Clarity Functions
* (multiply)
Introduced in: Clarity 1
input: int, ... | uint, ...
output: int | uint
signature: (* i1 i2...)
description:
Multiplies a variable number of integer inputs and returns the result. In the event of an overflow, throws a runtime error.
example:
+ (add)
Introduced in: Clarity 1
input: int, ... | uint, ...
output: int | uint
signature: (+ i1 i2...)
description:
Adds a variable number of integer inputs and returns the result. In the event of an overflow, throws a runtime error.
example:
- (subtract)
Introduced in: Clarity 1
input: int, ... | uint, ...
output: int | uint
signature: (- i1 i2...)
description:
Subtracts a variable number of integer inputs and returns the result. In the event of an underflow, throws a runtime error.
example:
/ (divide)
Introduced in: Clarity 1
input: int, ... | uint, ...
output: int | uint
signature: (/ i1 i2...)
description:
Integer divides a variable number of integer inputs and returns the result. In the event of division by zero, throws a runtime error.
example:
< (less than)
Introduced in: Clarity 1
input: int, int | uint, uint | string-ascii, string-ascii | string-utf8, string-utf8 | buff, buff
output: bool
signature: (< i1 i2)
description:
Compares two integers, returning true
if i1
is less than i2
and false
otherwise. i1 and i2 must be of the same type. Starting with Stacks 1.0, the <
-comparable types are int
and uint
. Starting with Stacks 2.1, the <
-comparable types are expanded to include string-ascii
, string-utf8
and buff
.
example:
<= (less than or equal)
Introduced in: Clarity 1
input: int, int | uint, uint | string-ascii, string-ascii | string-utf8, string-utf8 | buff, buff
output: bool
signature: (<= i1 i2)
description:
Compares two integers, returning true if i1
is less than or equal to i2
and false
otherwise. i1 and i2 must be of the same type. Starting with Stacks 1.0, the <=
-comparable types are int
and uint
. Starting with Stacks 2.1, the <=
-comparable types are expanded to include string-ascii
, string-utf8
and buff
.
example:
> (greater than)
Introduced in: Clarity 1
input: int, int | uint, uint | string-ascii, string-ascii | string-utf8, string-utf8 | buff, buff
output: bool
signature: (> i1 i2)
description:
Compares two integers, returning true
if i1
is greater than i2
and false otherwise. i1 and i2 must be of the same type. Starting with Stacks 1.0, the >
-comparable types are int
and uint
. Starting with Stacks 2.1, the >
-comparable types are expanded to include string-ascii
, string-utf8
and buff
.
example:
>= (greater than or equal)
Introduced in: Clarity 1
input: int, int | uint, uint | string-ascii, string-ascii | string-utf8, string-utf8 | buff, buff
output: bool
signature: (>= i1 i2)
description:
Compares two integers, returning true
if i1
is greater than or equal to i2
and false
otherwise. i1 and i2 must be of the same type. Starting with Stacks 1.0, the >=
-comparable types are int
and uint
. Starting with Stacks 2.1, the >=
-comparable types are expanded to include string-ascii
, string-utf8
and buff
.
example:
and
Introduced in: Clarity 1
input: bool, ...
output: bool
signature: (and b1 b2 ...)
description:
Returns true
if all boolean inputs are true
. Importantly, the supplied arguments are evaluated in-order and lazily. Lazy evaluation means that if one of the arguments returns false
, the function short-circuits, and no subsequent arguments are evaluated.
example:
append
Introduced in: Clarity 1
input: list A, A
output: list
signature: (append (list 1 2 3 4) 5)
description:
The append
function takes a list and another value with the same entry type, and outputs a list of the same type with max_len += 1.
example:
as-contract
Introduced in: Clarity 1
input: A
output: A
signature: (as-contract expr)
description:
The as-contract
function switches the current context's tx-sender
value to the contract's principal and executes expr
with that context. It returns the resulting value of expr
.
example:
as-max-len?
Introduced in: Clarity 1
input: sequence_A, uint
output: (optional sequence_A)
signature: (as-max-len? sequence max_length)
description:
The as-max-len?
function takes a sequence argument and a uint-valued, literal length argument. The function returns an optional type. If the input sequence length is less than or equal to the supplied max_length, this returns (some sequence)
, otherwise it returns none
. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
.
example:
asserts!
Introduced in: Clarity 1
input: bool, C
output: bool
signature: (asserts! bool-expr thrown-value)
description:
The asserts!
function admits a boolean argument and asserts its evaluation: if bool-expr is true
, asserts!
returns true
and proceeds in the program execution. If the supplied argument is returning a false value, asserts!
returns thrown-value
and exits the current control-flow.
example:
at-block
Introduced in: Clarity 1
input: (buff 32), A
output: A
signature: (at-block id-block-hash expr)
description:
The at-block
function evaluates the expression expr
as if it were evaluated at the end of the block indicated by the block-hash argument. The expr
closure must be read-only.
Note: The block identifying hash must be a hash returned by the id-header-hash
block information property. This hash uniquely identifies Stacks blocks and is unique across Stacks forks. While the hash returned by header-hash
is unique within the context of a single fork, it is not unique across Stacks forks.
The function returns the result of evaluating expr
.
example:
begin
Introduced in: Clarity 1
input: AnyType, ... A
output: A
signature: (begin expr1 expr2 expr3 ... expr-last)
description:
The begin
function evaluates each of its input expressions, returning the return value of the last such expression. Note: intermediary statements returning a response type must be checked.
example:
bit-and
Introduced in: Clarity 2
input: int, ... | uint, ...
output: int | uint
signature: (bit-and i1 i2...)
description:
Returns the result of bitwise and'ing a variable number of integer inputs.
example:
bit-not
Introduced in: Clarity 2
input: int | uint
output: int | uint
signature: (bit-not i1)
description:
Returns the one's complement (sometimes also called the bitwise compliment or not operator) of i1
, effectively reversing the bits in i1
. In other words, every bit that is 1
in ì1will be
0in the result. Conversely, every bit that is
0in
i1will be
1` in the result.
example:
bit-or
Introduced in: Clarity 2
input: int, ... | uint, ...
output: int | uint
signature: (bit-or i1 i2...)
description:
Returns the result of bitwise inclusive or'ing a variable number of integer inputs.
example:
bit-shift-left
Introduced in: Clarity 2
input: int, uint | uint, uint
output: int | uint
signature: (bit-shift-left i1 shamt)
description:
Shifts all the bits in i1
to the left by the number of places specified in shamt
modulo 128 (the bit width of Clarity integers).
Note that there is a deliberate choice made to ignore arithmetic overflow for this operation. In use cases where overflow should be detected, developers should use *
, /
, and pow
instead of the shift operators.
example:
bit-shift-right
Introduced in: Clarity 2
input: int, uint | uint, uint
output: int | uint
signature: (bit-shift-right i1 shamt)
description:
Shifts all the bits in i1
to the right by the number of places specified in shamt
modulo 128 (the bit width of Clarity integers). When i1
is a uint
(unsigned), new bits are filled with zeros. When i1
is an int
(signed), the sign is preserved, meaning that new bits are filled with the value of the previous sign-bit.
Note that there is a deliberate choice made to ignore arithmetic overflow for this operation. In use cases where overflow should be detected, developers should use *
, /
, and pow
instead of the shift operators.
example:
bit-xor
Introduced in: Clarity 2
input: int, ... | uint, ...
output: int | uint
signature: (bit-xor i1 i2...)
description:
Returns the result of bitwise exclusive or'ing a variable number of integer inputs.
example:
buff-to-int-be
Introduced in: Clarity 2
input: (buff 16)
output: int
signature: (buff-to-int-be (buff 16))
description:
Converts a byte buffer to a signed integer use a big-endian encoding. The byte buffer can be up to 16 bytes in length. If there are fewer than 16 bytes, as this function uses a big-endian encoding, the input behaves as if it is zero-padded on the left.
Note: This function is only available starting with Stacks 2.1.
example:
buff-to-int-le
Introduced in: Clarity 2
input: (buff 16)
output: int
signature: (buff-to-int-le (buff 16))
description:
Converts a byte buffer to a signed integer use a little-endian encoding. The byte buffer can be up to 16 bytes in length. If there are fewer than 16 bytes, as this function uses a little-endian encoding, the input behaves as if it is zero-padded on the right.
Note: This function is only available starting with Stacks 2.1.
example:
buff-to-uint-be
Introduced in: Clarity 2
input: (buff 16)
output: uint
signature: (buff-to-uint-be (buff 16))
description:
Converts a byte buffer to an unsigned integer use a big-endian encoding. The byte buffer can be up to 16 bytes in length. If there are fewer than 16 bytes, as this function uses a big-endian encoding, the input behaves as if it is zero-padded on the left.
Note: This function is only available starting with Stacks 2.1.
example:
buff-to-uint-le
Introduced in: Clarity 2
input: (buff 16)
output: uint
signature: (buff-to-uint-le (buff 16))
description:
Converts a byte buffer to an unsigned integer use a little-endian encoding.. The byte buffer can be up to 16 bytes in length. If there are fewer than 16 bytes, as this function uses a little-endian encoding, the input behaves as if it is zero-padded on the right.
Note: This function is only available starting with Stacks 2.1.
example:
concat
Introduced in: Clarity 1
input: sequence_A, sequence_A
output: sequence_A
signature: (concat sequence1 sequence2)
description:
The concat
function takes two sequences of the same type, and returns a concatenated sequence of the same type, with the resulting sequence_len = sequence1_len + sequence2_len. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
.
example:
contract-call?
Introduced in: Clarity 1
input: ContractName, PublicFunctionName, Arg0, ...
output: (response A B)
signature: (contract-call? .contract-name function-name arg0 arg1 ...)
description:
The contract-call?
function executes the given public function of the given contract. You may not use this function to call a public function defined in the current contract. If the public function returns err, any database changes resulting from calling contract-call?
are aborted. If the function returns ok, database changes occurred.
example:
contract-of
Introduced in: Clarity 1
input: Trait
output: principal
signature: (contract-of .contract-name)
description:
The contract-of
function returns the principal of the contract implementing the trait.
example:
default-to
Introduced in: Clarity 1
input: A, (optional A)
output: A
signature: (default-to default-value option-value)
description:
The default-to
function attempts to 'unpack' the second argument: if the argument is a (some ...)
option, it returns the inner value of the option. If the second argument is a (none)
value, default-to
it returns the value of default-value
.
example:
define-constant
Introduced in: Clarity 1
input: MethodSignature, MethodBody
output: Not Applicable
signature: (define-constant name expression)
description:
define-constant
is used to define a private constant value in a smart contract. The expression passed into the definition is evaluated at contract launch, in the order that it is supplied in the contract. This can lead to undefined function or undefined variable errors in the event that a function or variable used in the expression has not been defined before the constant.
Like other kinds of definition statements, define-constant
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
example:
define-data-var
Introduced in: Clarity 1
input: VarName, TypeDefinition, Value
output: Not Applicable
signature: (define-data-var var-name type value)
description:
define-data-var
is used to define a new persisted variable for use in a smart contract. Such variable are only modifiable by the current smart contract.
Persisted variable are defined with a type and a value.
Like other kinds of definition statements, define-data-var
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
example:
define-fungible-token
Introduced in: Clarity 1
input: TokenName, <uint>
output: Not Applicable
signature: (define-fungible-token token-name <total-supply>)
description:
define-fungible-token
is used to define a new fungible token class for use in the current contract.
The second argument, if supplied, defines the total supply of the fungible token. This ensures that all calls to the ft-mint?
function will never be able to create more than total-supply
tokens. If any such call were to increase the total supply of tokens passed that amount, that invocation of ft-mint?
will result in a runtime error and abort.
Like other kinds of definition statements, define-fungible-token
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
Tokens defined using define-fungible-token
may be used in ft-transfer?
, ft-mint?
, and ft-get-balance
functions
example:
define-map
Introduced in: Clarity 1
input: MapName, TypeDefinition, TypeDefinition
output: Not Applicable
signature: (define-map map-name key-type value-type)
description:
define-map
is used to define a new datamap for use in a smart contract. Such maps are only modifiable by the current smart contract.
Maps are defined with a key type and value type, often these types are tuple types.
Like other kinds of definition statements, define-map
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
example:
define-non-fungible-token
Introduced in: Clarity 1
input: AssetName, TypeSignature
output: Not Applicable
signature: (define-non-fungible-token asset-name asset-identifier-type)
description:
define-non-fungible-token
is used to define a new non-fungible token class for use in the current contract. Individual assets are identified by their asset identifier, which must be of the type asset-identifier-type
. Asset identifiers are unique identifiers.
Like other kinds of definition statements, define-non-fungible-token
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
Assets defined using define-non-fungible-token
may be used in nft-transfer?
, nft-mint?
, and nft-get-owner?
functions
example:
define-private
Introduced in: Clarity 1
input: MethodSignature, MethodBody
output: Not Applicable
signature: (define-private (function-name (arg-name-0 arg-type-0) (arg-name-1 arg-type-1) ...) function-body)
description:
define-private
is used to define private functions for a smart contract. Private functions may not be called from other smart contracts, nor may they be invoked directly by users. Instead, these functions may only be invoked by other functions defined in the same smart contract.
Like other kinds of definition statements, define-private
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
Private functions may return any type.
example:
define-public
Introduced in: Clarity 1
input: MethodSignature, MethodBody
output: Not Applicable
signature: (define-public (function-name (arg-name-0 arg-type-0) (arg-name-1 arg-type-1) ...) function-body)
description:
define-public
is used to define a public function and transaction for a smart contract. Public functions are callable from other smart contracts and may be invoked directly by users by submitting a transaction to the Stacks blockchain.
Like other kinds of definition statements, define-public
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
Public functions must return a ResponseType (using either ok
or err
). Any datamap modifications performed by a public function is aborted if the function returns an err
type. Public functions may be invoked by other contracts via contract-call?
.
example:
define-read-only
Introduced in: Clarity 1
input: MethodSignature, MethodBody
output: Not Applicable
signature: (define-read-only (function-name (arg-name-0 arg-type-0) (arg-name-1 arg-type-1) ...) function-body)
description:
define-read-only
is used to define a public read-only function for a smart contract. Such functions are callable from other smart contracts.
Like other kinds of definition statements, define-read-only
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
Read-only functions may return any type. However, read-only functions may not perform any datamap modifications, or call any functions which perform such modifications. This is enforced both during type checks and during the execution of the function. Public read-only functions may be invoked by other contracts via contract-call?
.
example:
define-trait
Introduced in: Clarity 1
input: VarName, [MethodSignature]
output: Not Applicable
signature: (define-trait trait-name ((func1-name (arg1-type arg2-type ...) (return-type))))
description:
define-trait
is used to define a new trait definition for use in a smart contract. Other contracts can implement a given trait and then have their contract identifier being passed as a function argument in order to be called dynamically with contract-call?
.
Traits are defined with a name, and a list functions, defined with a name, a list of argument types, and return type.
In Clarity 1, a trait type can be used to specify the type of a function parameter. A parameter with a trait type can be used as the target of a dynamic contract-call?
. A principal literal (e.g. ST1PQHQKV0RJXZFY1DGX8MNSNYVE3VGZJSRTPGZGM.foo
) may be passed as a trait parameter if the specified contract implements all of the functions specified by the trait. A trait value (originating from a parameter with trait type) may also be passed as a trait parameter if the types are the same.
Beginning in Clarity 2, a trait can be used in all of the same ways that a built-in type can be used, except that it cannot be stored in a data var or map, since this would inhibit static analysis. This means that a trait type can be embedded in a compound type (e.g. (optional <my-trait>)
or (list 4 <my-trait>)
) and a trait value can be bound to a variable in a let
or match
expression. In addition to the principal literal and trait value with matching type allowed in Clarity 1, Clarity 2 also supports implicit casting from a compatible trait, meaning that a value of type trait-a
may be passed to a parameter with type trait-b
if trait-a
includes all of the requirements of trait-b
(and optionally additional functions).
Like other kinds of definition statements, define-trait
may only be used at the top level of a smart contract definition (i.e., you cannot put a define statement in the middle of a function body).
example:
element-at
Introduced in: Clarity 1
input: sequence_A, uint
output: (optional A)
signature: (element-at? sequence index)
description:
The element-at?
function returns the element at index
in the provided sequence. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
, for which the corresponding element types are, respectively, A
, (buff 1)
, (string-ascii 1)
and (string-utf8 1)
. In Clarity1, element-at
must be used (without the ?
). The ?
is added in Clarity2 for consistency -- built-ins that return responses or optionals end in ?
. The Clarity1 spelling is left as an alias in Clarity2 for backwards compatibility.
example:
element-at?
Introduced in: Clarity 2
input: sequence_A, uint
output: (optional A)
signature: (element-at? sequence index)
description:
The element-at?
function returns the element at index
in the provided sequence. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
, for which the corresponding element types are, respectively, A
, (buff 1)
, (string-ascii 1)
and (string-utf8 1)
. In Clarity1, element-at
must be used (without the ?
). The ?
is added in Clarity2 for consistency -- built-ins that return responses or optionals end in ?
. The Clarity1 spelling is left as an alias in Clarity2 for backwards compatibility.
example:
err
Introduced in: Clarity 1
input: A
output: (response A B)
signature: (err value)
description:
The err
function constructs a response type from the input value. Use err
for creating return values in public functions. An err value indicates that any database changes during the processing of the function should be rolled back.
example:
filter
Introduced in: Clarity 1
input: Function(A) -> bool, sequence_A
output: sequence_A
signature: (filter func sequence)
description:
The filter
function applies the input function func
to each element of the input sequence, and returns the same sequence with any elements removed for which func
returned false
. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
, for which the corresponding element types are, respectively, A
, (buff 1)
, (string-ascii 1)
and (string-utf8 1)
. The func
argument must be a literal function name.
example:
fold
Introduced in: Clarity 1
input: Function(A, B) -> B, sequence_A, B
output: B
signature: (fold func sequence_A initial_B)
description:
The fold
function condenses sequence_A
into a value of type B
by recursively applies the function func
to each element of the input sequence and the output of a previous application of func
.
fold
uses initial_B
in the initial application of func
, along with the first element of sequence_A
. The resulting value of type B
is used for the next application of func
, along with the next element of sequence_A
and so on. fold
returns the last value of type B
returned by these successive applications func
.
Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
, for which the corresponding element types are, respectively, A
, (buff 1)
, (string-ascii 1)
and (string-utf8 1)
. The func
argument must be a literal function name.
example:
from-consensus-buff?
Introduced in: Clarity 2
input: type-signature(t), buff
output: (optional t)
signature: (from-consensus-buff? type-signature buffer)
description:
from-consensus-buff?
is a special function that will deserialize a buffer into a Clarity value, using the SIP-005 serialization of the Clarity value. The type that from-consensus-buff?
tries to deserialize into is provided by the first parameter to the function. If it fails to deserialize the type, the method returns none
.
example:
ft-burn?
Introduced in: Clarity 1
input: TokenName, uint, principal
output: (response bool uint)
signature: (ft-burn? token-name amount sender)
description:
ft-burn?
is used to decrease the token balance for the sender
principal for a token type defined using define-fungible-token
. The decreased token balance is not transferred to another principal, but rather destroyed, reducing the circulating supply.
On a successful burn, it returns (ok true)
. In the event of an unsuccessful burn it returns one of the following error codes:
(err u1)
-- sender
does not have enough balance to burn this amount or the amount specified is not positive
example:
ft-get-balance
Introduced in: Clarity 1
input: TokenName, principal
output: uint
signature: (ft-get-balance token-name principal)
description:
ft-get-balance
returns token-name
balance of the principal principal
. The token type must have been defined using define-fungible-token
.
example:
ft-get-supply
Introduced in: Clarity 1
input: TokenName
output: uint
signature: (ft-get-supply token-name)
description:
ft-get-balance
returns token-name
circulating supply. The token type must have been defined using define-fungible-token
.
example:
ft-mint?
Introduced in: Clarity 1
input: TokenName, uint, principal
output: (response bool uint)
signature: (ft-mint? token-name amount recipient)
description:
ft-mint?
is used to increase the token balance for the recipient
principal for a token type defined using define-fungible-token
. The increased token balance is not transfered from another principal, but rather minted.
If a non-positive amount is provided to mint, this function returns (err 1)
. Otherwise, on successfully mint, it returns (ok true)
.
example:
ft-transfer?
Introduced in: Clarity 1
input: TokenName, uint, principal, principal
output: (response bool uint)
signature: (ft-transfer? token-name amount sender recipient)
description:
ft-transfer?
is used to increase the token balance for the recipient
principal for a token type defined using define-fungible-token
by debiting the sender
principal. In contrast to stx-transfer?
, any user can transfer the assets. When used, relevant guards need to be added.
This function returns (ok true) if the transfer is successful. In the event of an unsuccessful transfer it returns one of the following error codes:
(err u1)
-- sender
does not have enough balance to transfer (err u2)
-- sender
and recipient
are the same principal (err u3)
-- amount to send is non-positive
example:
get
Introduced in: Clarity 1
input: KeyName, (tuple) | (optional (tuple))
output: A
signature: (get key-name tuple)
description:
The get
function fetches the value associated with a given key from the supplied typed tuple. If an Optional
value is supplied as the inputted tuple, get
returns an Optional
type of the specified key in the tuple. If the supplied option is a (none)
option, get returns (none)
.
example:
get-block-info?
Introduced in: Clarity 1
input: BlockInfoPropertyName, uint
output: (optional buff) | (optional uint)
signature: (get-block-info? prop-name block-height)
description:
The get-block-info?
function fetches data for a block of the given Stacks block height. The value and type returned are determined by the specified BlockInfoPropertyName
. If the provided block-height
does not correspond to an existing block prior to the current block, the function returns none
. The currently available property names are as follows:
burnchain-header-hash
: This property returns a (buff 32)
value containing the header hash of the burnchain (Bitcoin) block that selected the Stacks block at the given Stacks chain height.
id-header-hash
: This property returns a (buff 32)
value containing the index block hash of a Stacks block. This hash is globally unique, and is derived from the block hash and the history of accepted PoX operations. This is also the block hash value you would pass into (at-block)
.
header-hash
: This property returns a (buff 32)
value containing the header hash of a Stacks block, given a Stacks chain height. *WARNING this hash is not guaranteed to be globally unique, since the same Stacks block can be mined in different PoX forks. If you need global uniqueness, you should use id-header-hash
.
miner-address
: This property returns a principal
value corresponding to the miner of the given block. WARNING In Stacks 2.1, this is not guaranteed to be the same principal
that received the block reward, since Stacks 2.1 supports coinbase transactions that pay the reward to a contract address. This is merely the address of the principal
that produced the block.
time
: This property returns a uint
value of the block header time field. This is a Unix epoch timestamp in seconds which roughly corresponds to when the block was mined. Note: this does not increase monotonically with each block and block times are accurate only to within two hours. See BIP113 for more information.
New in Stacks 2.1:
block-reward
: This property returns a uint
value for the total block reward of the indicated Stacks block. This value is only available once the reward for the block matures. That is, the latest block-reward
value available is at least 101 Stacks blocks in the past (on mainnet). The reward includes the coinbase, the anchored block's transaction fees, and the shares of the confirmed and produced microblock transaction fees earned by this block's miner. Note that this value may be smaller than the Stacks coinbase at this height, because the miner may have been punished with a valid PoisonMicroblock
transaction in the event that the miner published two or more microblock stream forks.
miner-spend-total
: This property returns a uint
value for the total number of burnchain tokens (i.e. satoshis) spent by all miners trying to win this block.
miner-spend-winner
: This property returns a uint
value for the number of burnchain tokens (i.e. satoshis) spent by the winning miner for this Stacks block. Note that this value is less than or equal to the value for miner-spend-total
at the same block height.
example:
get-burn-block-info?
Introduced in: Clarity 2
input: BurnBlockInfoPropertyName, uint
output: (optional buff) | (optional (tuple (addrs (list 2 (tuple (hashbytes (buff 32)) (version (buff 1))))) (payout uint)))
signature: (get-burn-block-info? prop-name block-height)
description:
The get-burn-block-info?
function fetches data for a block of the given burnchain block height. The value and type returned are determined by the specified BlockInfoPropertyName
. Valid values for block-height
only include heights between the burnchain height at the time the Stacks chain was launched, and the last-processed burnchain block. If the block-height
argument falls outside of this range, then none
shall be returned.
The following BlockInfoPropertyName
values are defined:
The
header-hash
property returns a 32-byte buffer representing the header hash of the burnchain block at burnchain heightblock-height
.The
pox-addrs
property returns a tuple with two items: a list of up to two PoX addresses that received a PoX payout at that block height, and the amount of burnchain tokens paid to each address (note that per the blockchain consensus rules, each PoX payout will be the same for each address in the block-commit transaction). The list will include burn addresses -- that is, the unspendable addresses that miners pay to when there are no PoX addresses left to be paid. During the prepare phase, there will be exactly one burn address reported. During the reward phase, up to two burn addresses may be reported in the event that some PoX reward slots are not claimed.
The addrs
list contains the same PoX address values passed into the PoX smart contract:
They each have type signature
(tuple (hashbytes (buff 32)) (version (buff 1)))
The
version
field can be any of the following:0x00
means this is a p2pkh address, andhashbytes
is the 20-byte hash160 of a single public key0x01
means this is a p2sh address, andhashbytes
is the 20-byte hash160 of a redeemScript script0x02
means this is a p2wpkh-p2sh address, andhashbytes
is the 20-byte hash160 of a p2wpkh witness script0x03
means this is a p2wsh-p2sh address, andhashbytes
is the 20-byte hash160 of a p2wsh witness script0x04
means this is a p2wpkh address, andhashbytes
is the 20-byte hash160 of the witness script0x05
means this is a p2wsh address, andhashbytes
is the 32-byte sha256 of the witness script0x06
means this is a p2tr address, andhashbytes
is the 32-byte sha256 of the witness script
example:
hash160
Introduced in: Clarity 1
input: buff|uint|int
output: (buff 20)
signature: (hash160 value)
description:
The hash160
function computes RIPEMD160(SHA256(x))
of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.
example:
if
Introduced in: Clarity 1
input: bool, A, A
output: A
signature: (if bool1 expr1 expr2)
description:
The if
function admits a boolean argument and two expressions which must return the same type. In the case that the boolean input is true
, the if
function evaluates and returns expr1
. If the boolean input is false
, the if
function evaluates and returns expr2
.
example:
impl-trait
Introduced in: Clarity 1
input: TraitIdentifier
output: Not Applicable
signature: (impl-trait trait-identifier)
description:
impl-trait
can be use for asserting that a contract is fully implementing a given trait. Additional checks are being performed when the contract is being published, rejecting the deployment if the contract is violating the trait specification.
Trait identifiers can either be using the sugared syntax (.token-a.token-trait), or be fully qualified ('SPAXYA5XS51713FDTQ8H94EJ4V579CXMTRNBZKSF.token-a.token-trait).
Like other kinds of definition statements, impl-trait
may only be used at the top level of a smart contract definition (i.e., you cannot put such a statement in the middle of a function body).
example:
index-of
Introduced in: Clarity 1
input: sequence_A, A
output: (optional uint)
signature: (index-of? sequence item)
description:
The index-of?
function returns the first index at which item
can be found, using is-eq
checks, in the provided sequence. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
, for which the corresponding element types are, respectively, A
, (buff 1)
, (string-ascii 1)
and (string-utf8 1)
. If the target item is not found in the sequence (or if an empty string or buffer is supplied), this function returns none
. In Clarity1, index-of
must be used (without the ?
). The ?
is added in Clarity2 for consistency -- built-ins that return responses or optionals end in ?
. The Clarity1 spelling is left as an alias in Clarity2 for backwards compatibility.
example:
index-of?
Introduced in: Clarity 2
input: sequence_A, A
output: (optional uint)
signature: (index-of? sequence item)
description:
The index-of?
function returns the first index at which item
can be found, using is-eq
checks, in the provided sequence. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
, for which the corresponding element types are, respectively, A
, (buff 1)
, (string-ascii 1)
and (string-utf8 1)
. If the target item is not found in the sequence (or if an empty string or buffer is supplied), this function returns none
. In Clarity1, index-of
must be used (without the ?
). The ?
is added in Clarity2 for consistency -- built-ins that return responses or optionals end in ?
. The Clarity1 spelling is left as an alias in Clarity2 for backwards compatibility.
example:
int-to-ascii
Introduced in: Clarity 2
input: int | uint
output: (string-ascii 40)
signature: (int-to-ascii (int|uint))
description:
Converts an integer, either int
or uint
, to a string-ascii
string-value representation.
Note: This function is only available starting with Stacks 2.1.
example:
int-to-utf8
Introduced in: Clarity 2
input: int | uint
output: (string-utf8 40)
signature: (int-to-utf8 (int|uint))
description:
Converts an integer, either int
or uint
, to a string-utf8
string-value representation.
Note: This function is only available starting with Stacks 2.1.
example:
is-eq
Introduced in: Clarity 1
input: A, A, ...
output: bool
signature: (is-eq v1 v2...)
description:
Compares the inputted values, returning true
if they are all equal. Note that unlike the (and ...)
function, (is-eq ...)
will not short-circuit. All values supplied to is-eq must be the same type.
example:
is-err
Introduced in: Clarity 1
input: (response A B)
output: bool
signature: (is-err value)
description:
is-err
tests a supplied response value, returning true
if the response was an err
, and false
if it was an ok
.
example:
is-none
Introduced in: Clarity 1
input: (optional A)
output: bool
signature: (is-none value)
description:
is-none
tests a supplied option value, returning true
if the option value is (none)
, and false
if it is a (some ...)
.
example:
is-ok
Introduced in: Clarity 1
input: (response A B)
output: bool
signature: (is-ok value)
description:
is-ok
tests a supplied response value, returning true
if the response was ok
, and false
if it was an err
.
example:
is-some
Introduced in: Clarity 1
input: (optional A)
output: bool
signature: (is-some value)
description:
is-some
tests a supplied option value, returning true
if the option value is (some ...)
, and false
if it is a none
.
example:
is-standard
Introduced in: Clarity 2
input: principal
output: bool
signature: (is-standard standard-or-contract-principal)
description:
Tests whether standard-or-contract-principal
matches the current network type, and therefore represents a principal that can spend tokens on the current network type. That is, the network is either of type mainnet
, or testnet
. Only SPxxxx
and SMxxxx
c32check form addresses can spend tokens on a mainnet, whereas only STxxxx
and SNxxxx
c32check forms addresses can spend tokens on a testnet. All addresses can receive tokens, but only principal c32check form addresses that match the network type can spend tokens on the network. This method will return true
if and only if the principal matches the network type, and false otherwise.
Note: This function is only available starting with Stacks 2.1.
example:
keccak256
Introduced in: Clarity 1
input: buff|uint|int
output: (buff 32)
signature: (keccak256 value)
description:
The keccak256
function computes KECCAK256(value)
of the inputted value. Note that this differs from the NIST SHA-3
(that is, FIPS 202) standard. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.
example:
len
Introduced in: Clarity 1
input: sequence_A
output: uint
signature: (len sequence)
description:
The len
function returns the length of a given sequence. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
.
example:
let
Introduced in: Clarity 1
input: ((name1 AnyType) (name2 AnyType) ...), AnyType, ... A
output: A
signature: (let ((name1 expr1) (name2 expr2) ...) expr-body1 expr-body2 ... expr-body-last)
description:
The let
function accepts a list of variable name
and expression
pairs, evaluating each expression and binding it to the corresponding variable name. let
bindings are sequential: when a let
binding is evaluated, it may refer to prior binding. The context created by this set of bindings is used for evaluating its body expressions. The let expression returns the value of the last such body expression. Note: intermediary statements returning a response type must be checked
example:
list
Introduced in: Clarity 1
input: A, ...
output: (list A)
signature: (list expr1 expr2 expr3 ...)
description:
The list
function constructs a list composed of the inputted values. Each supplied value must be of the same type.
example:
log2
Introduced in: Clarity 1
input: int | uint
output: int | uint
signature: (log2 n)
description:
Returns the power to which the number 2 must be raised to to obtain the value n
, rounded down to the nearest integer. Fails on a negative numbers.
example:
map
Introduced in: Clarity 1
input: Function(A, B, ..., N) -> X, sequence_A, sequence_B, ..., sequence_N
output: (list X)
signature: (map func sequence_A sequence_B ... sequence_N)
description:
The map
function applies the function func
to each corresponding element of the input sequences, and outputs a list of the same type containing the outputs from those function applications. Applicable sequence types are (list A)
, buff
, string-ascii
and string-utf8
, for which the corresponding element types are, respectively, A
, (buff 1)
, (string-ascii 1)
and (string-utf8 1)
. The func
argument must be a literal function name. Also, note that, no matter what kind of sequences the inputs are, the output is always a list.
example:
map-delete
Introduced in: Clarity 1
input: MapName, tuple
output: bool
signature: (map-delete map-name key-tuple)
description:
The map-delete
function removes the value associated with the input key for the given map. If an item exists and is removed, the function returns true
. If a value did not exist for this key in the data map, the function returns false
.
example:
map-get?
Introduced in: Clarity 1
input: MapName, tuple
output: (optional (tuple))
signature: (map-get? map-name key-tuple)
description:
The map-get?
function looks up and returns an entry from a contract's data map. The value is looked up using key-tuple
. If there is no value associated with that key in the data map, the function returns a none
option. Otherwise, it returns (some value)
.
example:
map-insert
Introduced in: Clarity 1
input: MapName, tuple_A, tuple_B
output: bool
signature: (map-insert map-name key-tuple value-tuple)
description:
The map-insert
function sets the value associated with the input key to the inputted value if and only if there is not already a value associated with the key in the map. If an insert occurs, the function returns true
. If a value already existed for this key in the data map, the function returns false
.
Note: the value-tuple
requires 1 additional byte for storage in the materialized blockchain state, and therefore the maximum size of a value that may be inserted into a map is MAX_CLARITY_VALUE - 1.
example:
map-set
Introduced in: Clarity 1
input: MapName, tuple_A, tuple_B
output: bool
signature: (map-set map-name key-tuple value-tuple)
description:
The map-set
function sets the value associated with the input key to the inputted value. This function performs a blind update; whether or not a value is already associated with the key, the function overwrites that existing association.
Note: the value-tuple
requires 1 additional byte for storage in the materialized blockchain state, and therefore the maximum size of a value that may be inserted into a map is MAX_CLARITY_VALUE - 1.
example:
match
Introduced in: Clarity 1
input: (optional A) name expression expression | (response A B) name expression name expression
output: C
signature: (match opt-input some-binding-name some-branch none-branch) | (match-resp input ok-binding-name ok-branch err-binding-name err-branch)
description:
The match
function is used to test and destructure optional and response types.
If the input
is an optional, it tests whether the provided input
is a some
or none
option, and evaluates some-branch
or none-branch
in each respective case.
Within the some-branch
, the contained value of the input
argument is bound to the provided some-binding-name
name.
Only one of the branches will be evaluated (similar to if
statements).
If the input
is a response, it tests whether the provided input
is an ok
or err
response type, and evaluates ok-branch
or err-branch
in each respective case.
Within the ok-branch
, the contained ok value of the input
argument is bound to the provided ok-binding-name
name.
Within the err-branch
, the contained err value of the input
argument is bound to the provided err-binding-name
name.
Only one of the branches will be evaluated (similar to if
statements).
Note: Type checking requires that the type of both the ok and err parts of the response object be determinable. For situations in which one of the parts of a response is untyped, you should use unwrap-panic
or unwrap-err-panic
instead of match
.
example:
merge
Introduced in: Clarity 1
input: tuple, tuple
output: tuple
signature: (merge tuple { key1: val1 })
description:
The merge
function returns a new tuple with the combined fields, without mutating the supplied tuples.
example:
mod
Introduced in: Clarity 1
input: int, int | uint, uint | string-ascii, string-ascii | string-utf8, string-utf8 | buff, buff
output: int | uint
signature: (mod i1 i2)
description:
Returns the integer remainder from integer dividing i1
by i2
. In the event of a division by zero, throws a runtime error.
example:
nft-burn?
Introduced in: Clarity 1
input: AssetName, A, principal
output: (response bool uint)
signature: (nft-burn? asset-class asset-identifier sender)
description:
nft-burn?
is used to burn an asset that the sender
principal owns. The asset must have been defined using define-non-fungible-token
, and the supplied asset-identifier
must be of the same type specified in that definition.
On a successful burn, it returns (ok true)
. In the event of an unsuccessful burn it returns one of the following error codes:
(err u1)
-- sender
does not own the specified asset (err u3)
-- the asset specified by asset-identifier
does not exist
example:
nft-get-owner?
Introduced in: Clarity 1
input: AssetName, A
output: (optional principal)
signature: (nft-get-owner? asset-class asset-identifier)
description:
nft-get-owner?
returns the owner of an asset, identified by asset-identifier
, or none
if the asset does not exist. The asset type must have been defined using define-non-fungible-token
, and the supplied asset-identifier
must be of the same type specified in that definition.
example:
nft-mint?
Introduced in: Clarity 1
input: AssetName, A, principal
output: (response bool uint)
signature: (nft-mint? asset-class asset-identifier recipient)
description:
nft-mint?
is used to instantiate an asset and set that asset's owner to the recipient
principal. The asset must have been defined using define-non-fungible-token
, and the supplied asset-identifier
must be of the same type specified in that definition.
If an asset identified by asset-identifier
already exists, this function will return an error with the following error code:
(err u1)
Otherwise, on successfuly mint, it returns (ok true)
.
example:
nft-transfer?
Introduced in: Clarity 1
input: AssetName, A, principal, principal
output: (response bool uint)
signature: (nft-transfer? asset-class asset-identifier sender recipient)
description:
nft-transfer?
is used to change the owner of an asset identified by asset-identifier
from sender
to recipient
. The asset-class
must have been defined by define-non-fungible-token
and asset-identifier
must be of the type specified in that definition. In contrast to stx-transfer?
, any user can transfer the asset. When used, relevant guards need to be added.
This function returns (ok true) if the transfer is successful. In the event of an unsuccessful transfer it returns one of the following error codes:
(err u1)
-- sender
does not own the asset (err u2)
-- sender
and recipient
are the same principal (err u3)
-- asset identified by asset-identifier does not exist
example:
not
Introduced in: Clarity 1
input: bool
output: bool
signature: (not b1)
description:
Returns the inverse of the boolean input.
example:
ok
Introduced in: Clarity 1
input: A
output: (response A B)
signature: (ok value)
description:
The ok
function constructs a response type from the input value. Use ok
for creating return values in public functions. An ok value indicates that any database changes during the processing of the function should materialize.
example:
or
Introduced in: Clarity 1
input: bool, ...
output: bool
signature: (or b1 b2 ...)
description:
Returns true
if any boolean inputs are true
. Importantly, the supplied arguments are evaluated in-order and lazily. Lazy evaluation means that if one of the arguments returns true
, the function short-circuits, and no subsequent arguments are evaluated.
example:
pow
Introduced in: Clarity 1
input: int, int | uint, uint | string-ascii, string-ascii | string-utf8, string-utf8 | buff, buff
output: int | uint
signature: (pow i1 i2)
description:
Returns the result of raising i1
to the power of i2
. In the event of an overflow, throws a runtime error. Note: Corner cases are handled with the following rules:
if both
i1
andi2
are0
, return1
if
i1
is1
, return1
if
i1
is0
, return0
if
i2
is1
, returni1
if
i2
is negative or greater thanu32::MAX
, throw a runtime error
example:
principal-construct?
Introduced in: Clarity 2
input: (buff 1), (buff 20), [(string-ascii 40)]
output: (response principal { error_code: uint, principal: (option principal) })
signature: (principal-construct? (buff 1) (buff 20) [(string-ascii 40)])
description:
A principal value represents either a set of keys, or a smart contract. The former, called a standard principal, is encoded as a (buff 1)
version byte, indicating the type of account and the type of network that this principal can spend tokens on, and a (buff 20)
public key hash, characterizing the principal's unique identity. The latter, a contract principal, is encoded as a standard principal concatenated with a (string-ascii 40)
contract name that identifies the code body.
The principal-construct?
function allows users to create either standard or contract principals, depending on which form is used. To create a standard principal, principal-construct?
would be called with two arguments: it takes as input a (buff 1)
which encodes the principal address's version-byte
, a (buff 20)
which encodes the principal address's hash-bytes
. To create a contract principal, principal-construct?
would be called with three arguments: the (buff 1)
and (buff 20)
to represent the standard principal that created the contract, and a (string-ascii 40)
which encodes the contract's name. On success, this function returns either a standard principal or contract principal, depending on whether or not the third (string-ascii 40)
argument is given.
This function returns a Response
. On success, the ok
value is a Principal
. The err
value is a value tuple with the form { error_code: uint, value: (optional principal) }
.
If the single-byte version-byte
is in the valid range 0x00
to 0x1f
, but is not an appropriate version byte for the current network, then the error will be u0
, and value
will contain (some principal)
, where the wrapped value is the principal. If the version-byte
is not in this range, however, then the value
will be none
.
If the version-byte
is a buff
of length 0, if the single-byte version-byte
is a value greater than 0x1f
, or the hash-bytes
is a buff
of length not equal to 20, then error_code
will be u1
and value
will be None
.
If a name is given, and the name is either an empty string or contains ASCII characters that are not allowed in contract names, then error_code
will be u2
.
Note: This function is only available starting with Stacks 2.1.
example:
principal-destruct?
Introduced in: Clarity 2
input: principal
output: (response (tuple (hash-bytes (buff 20)) (name (optional (string-ascii 40))) (version (buff 1))) (tuple (hash-bytes (buff 20)) (name (optional (string-ascii 40))) (version (buff 1))))
signature: (principal-destruct? principal-address)
description:
A principal value represents either a set of keys, or a smart contract. The former, called a standard principal, is encoded as a (buff 1)
version byte, indicating the type of account and the type of network that this principal can spend tokens on, and a (buff 20)
public key hash, characterizing the principal's unique identity. The latter, a contract principal, is encoded as a standard principal concatenated with a (string-ascii 40)
contract name that identifies the code body.
principal-destruct?
will decompose a principal into its component parts: either{version-byte, hash-bytes}
for standard principals, or {version-byte, hash-bytes, name}
for contract principals.
This method returns a Response
that wraps this data as a tuple.
If the version byte of principal-address
matches the network (see is-standard
), then this method returns the pair as its ok
value.
If the version byte of principal-address
does not match the network, then this method returns the pair as its err
value.
In both cases, the value itself is a tuple containing three fields: a version
value as a (buff 1)
, a hash-bytes
value as a (buff 20)
, and a name
value as an (optional (string-ascii 40))
. The name
field will only be (some ..)
if the principal is a contract principal.
Note: This function is only available starting with Stacks 2.1.
example:
principal-of?
Introduced in: Clarity 1
input: (buff 33)
output: (response principal uint)
signature: (principal-of? public-key)
description:
The principal-of?
function returns the principal derived from the provided public key. If the public-key
is invalid, it will return the error code (err u1).
.
Note: Before Stacks 2.1, this function has a bug, in that the principal returned would always be a testnet single-signature principal, even if the function were run on the mainnet. Starting with Stacks 2.1, this bug is fixed, so that this function will return a principal suited to the network it is called on. In particular, if this is called on the mainnet, it will return a single-signature mainnet principal.
example:
print
Introduced in: Clarity 1
input: A
output: A
signature: (print expr)
description:
The print
function evaluates and returns its input expression. On Stacks Core nodes configured for development (as opposed to production mining nodes), this function prints the resulting value to STDOUT
(standard output).
example:
replace-at?
Introduced in: Clarity 2
input: sequence_A, uint, A
output: (optional sequence_A)
signature: (replace-at? sequence index element)
description:
The replace-at?
function takes in a sequence, an index, and an element, and returns a new sequence with the data at the index position replaced with the given element. The given element's type must match the type of the sequence, and must correspond to a single index of the input sequence. The return type on success is the same type as the input sequence.
If the provided index is out of bounds, this functions returns none
.
example:
secp256k1-recover?
Introduced in: Clarity 1
input: (buff 32), (buff 65)
output: (response (buff 33) uint)
signature: (secp256k1-recover? message-hash signature)
description:
The secp256k1-recover?
function recovers the public key used to sign the message which sha256 is message-hash
with the provided signature
. If the signature does not match, it will return the error code (err u1).
. If the signature is invalid, it will return the error code (err u2).
. The signature includes 64 bytes plus an additional recovery id (00..03) for a total of 65 bytes.
example:
secp256k1-verify
Introduced in: Clarity 1
input: (buff 32), (buff 64) | (buff 65), (buff 33)
output: bool
signature: (secp256k1-verify message-hash signature public-key)
description:
The secp256k1-verify
function verifies that the provided signature of the message-hash was signed with the private key that generated the public key. The message-hash
is the sha256
of the message. The signature includes 64 bytes plus an optional additional recovery id (00..03) for a total of 64 or 65 bytes.
example:
sha256
Introduced in: Clarity 1
input: buff|uint|int
output: (buff 32)
signature: (sha256 value)
description:
The sha256
function computes SHA256(x)
of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.
example:
sha512
Introduced in: Clarity 1
input: buff|uint|int
output: (buff 64)
signature: (sha512 value)
description:
The sha512
function computes SHA512(x)
of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.
example:
sha512/256
Introduced in: Clarity 1
input: buff|uint|int
output: (buff 32)
signature: (sha512/256 value)
description:
The sha512/256
function computes SHA512/256(x)
(the SHA512 algorithm with the 512/256 initialization vector, truncated to 256 bits) of the inputted value. If an integer (128 bit) is supplied the hash is computed over the little-endian representation of the integer.
example:
slice?
Introduced in: Clarity 2
input: sequence_A, uint, uint
output: (optional sequence_A)
signature: (slice? sequence left-position right-position)
description:
The slice?
function attempts to return a sub-sequence of that starts at left-position
(inclusive), and ends at right-position
(non-inclusive). If left_position
==right_position
, the function returns an empty sequence. If either left_position
or right_position
are out of bounds OR if right_position
is less than left_position
, the function returns none
.
example:
some
Introduced in: Clarity 1
input: A
output: (optional A)
signature: (some value)
description:
The some
function constructs a optional
type from the input value.
example:
sqrti
Introduced in: Clarity 1
input: int | uint
output: int | uint
signature: (sqrti n)
description:
Returns the largest integer that is less than or equal to the square root of n
.
Fails on a negative numbers.
example:
string-to-int?
Introduced in: Clarity 2
input: (string-ascii 1048576) | (string-utf8 262144)
output: (optional int)
signature: (string-to-int? (string-ascii|string-utf8))
description:
Converts a string, either string-ascii
or string-utf8
, to an optional-wrapped signed integer. If the input string does not represent a valid integer, then the function returns none
. Otherwise it returns an integer wrapped in some
.
Note: This function is only available starting with Stacks 2.1.
example:
string-to-uint?
Introduced in: Clarity 2
input: (string-ascii 1048576) | (string-utf8 262144)
output: (optional uint)
signature: (string-to-uint? (string-ascii|string-utf8))
description:
Converts a string, either string-ascii
or string-utf8
, to an optional-wrapped unsigned integer. If the input string does not represent a valid integer, then the function returns none
. Otherwise it returns an unsigned integer wrapped in some
.
Note: This function is only available starting with Stacks 2.1.
example: