@lang:len

Length of a value: element count for an array, byte length for a string or bytes.

Returns: number

Syntax

@lang:len(value)

Arguments

Name	Type	Description
value	array	Source array, string or bytes value

See Also

• @at — access element by index
• @slice — extract a sub-array
• @str.len — string length

On-chain face (@len!)

The element count of a literal, live fixed-size or dynamic array, or nested collection helper. For a call returning string/bytes, return its decoded byte length.

Examples

load lang

set $gov 0xc0dbDcA66a0636236fAbe1B3C16B1bD4C84bB1E1

# Top level: compiles to a core nav ending in the LEN sentinel
assert @len!($gov::!{voters()(address[])}) >= 3 "not enough voters"
assert @len!($gov::!{voters()(address[])}) != 0

# Nested: the same LEN-sentinel nav, composable as a number
assert @calc!(@len!($gov::!{voters()(address[])}) * 2) > 4

Notes

• For a string/bytes return the decoded length is the byte length (UTF-8 characters may span multiple bytes). For raw returndata size use @bytes.len!.
• Over a nested collection helper (@len!(@filter!(…)), @len!(@safe:owners!())) the length is the live element count. Pairs count as one element. Generic pipelines can return their count without first packing the final array; byte lengths of string/bytes helpers stay with @bytes.len!/@str.len!.

See Also

• assert, @bytes.len!

Return-value lenses can select whole fixed arrays, including inside tuples and other arrays. The full selected value must be present; a truncated return reverts even when its declared fixed length is known at compile time.