@lang:flat

Flatten one level of nesting in an array.

On-chain (@lang:flat!): Up to 4 elements may be live calls, the rest constant arrays; each live element past the first is re-resolved by every later offset.

Returns: array

Syntax

@lang:flat(arr)

Arguments

Name	Type	Description
arr	array	Source array of arrays

See Also

• @concat — concatenate arrays
• @map — transform then flatten with @flat(@map(...))

On-chain face (@flat!)

Concatenate the word payloads of an array literal's parts on-chain through Operators.concat. Parts are constant arrays or :: call parts.

Up to four parts may be live. The envelopes splice into the calldata in order at the end, and each offset after the first live part is itself a live word: the constant base plus the running total of the earlier payloads, rounded up to whole words. A part may still sit at any logical position, since its ABI offset points at the splice rather than at where it reads.

Four is a hard limit rather than a guideline. An operand expression is a tree with no way to name a subterm, so each live part is re-resolved by every offset that follows it — source call included — which is N(N-1)/2 extra resolutions and a calldata blob growing with the square. An assertion is judged inside an eth_call, so an over-budget expression runs out of gas and reverts, and a reverted judge cannot be told apart from one that legitimately failed. Better to refuse at build time.

Examples

load lang

set $safe 0x44fA8E6f47987339850636F88629646662444217

assert @flat!([[1 2] $safe::{caps()(uint256[])}]) == 0x1122

See Also

• assert, @concat!