Blocks & Batching

Blocks

Some commands accept a block of sub-commands in parentheses:

batch (
  exec 0x44fA8E6f47987339850636F88629646662444217 "foo()"
  exec 0x0102030405060708090a0b0c0d0e0f1011121314 "bar()"
)

loop $i of @arr(0 5) (
  print $i
)

set $x 10
if @bool($x > 0) (
  print "positive"
) (
  print "non-positive"
)

A block does not change name resolution — what a command name means is decided by load import lists and defs alone, never by the block it appears in (see Modules & Imports).

Batching

By default, each exec command produces a separate transaction. A script like:

load token

set $router 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D

exec @token(DAI) "approve(address,uint256)" $router @token:amount(DAI 1000)
exec $router "swap(address,uint256)" @token(DAI) @token:amount(DAI 1000)

submits two separate transactions — the second could fail independently of the first. Wrap commands in batch to combine them into one atomic transaction:

load token

set $router 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D

batch (
  exec @token(DAI) "approve(address,uint256)" $router @token:amount(DAI 1000)
  exec $router "swap(address,uint256)" @token(DAI) @token:amount(DAI 1000)
)

Both the approve and swap happen atomically — if either fails, both revert.

When to Use Batch

• Approve + action: Approve a token and use it in the same tx
• Multi-step operations: Multiple related state changes that should be atomic
• Gas efficiency: Save gas by avoiding multiple transaction submissions
• Safety: Ensure all-or-nothing execution of related operations

Event Captures on Batches

You can capture events emitted during the entire batch:

set $wxdai 0xe91D153E0b41518A2Ce8Dd3D7944Fa863463a97d

batch (
  exec $wxdai "deposit()" --value 0.001e18
  exec $wxdai "withdraw(uint)" 0.001e18
) -> Deposit(address indexed, uint) [_ $amount]

A batch executes as one transaction, so a tx capture on it binds a single hash for the whole bundle:

set $wxdai 0xe91D153E0b41518A2Ce8Dd3D7944Fa863463a97d

batch (
  exec $wxdai "deposit()" --value 0.001e18
  exec $wxdai "withdraw(uint)" 0.001e18
) $> $tx

Error Captures on Batches

You can capture revert errors from the entire batch. All three forms from Event & Error Captures work: assertion only, destructure, or boolean variable.

set $token 0x9C58BAcC331c9aa871AFD802DB6379a98e80CEdb

# Destructure the error reason
batch (
  exec $token "transfer(address,uint256)" @me 100e18
) -!> Error(string) [$reason]

# Assert a specific error without capturing data
batch (
  exec $token "transfer(address,uint256)" @me 100e18
) -!> Unauthorized()

# Boolean variable with optional capture
batch (
  exec $token "transfer(address,uint256)" @me 100e18
) -?!> Unauthorized() $reverted

Nested Batching

Batches can contain control flow and other constructs:

load token

set $recipients [0x4F2083f5fBede34C2714aFfb3105539775f7FE64 0x64c007ba4ab6184753dc1e8e7263e8d06831c5f6]

batch (
  loop $addr of $recipients (
    exec @token(DAI) "transfer(address,uint256)" $addr @token:amount(DAI 100)
  )
)