Multiple results in WebAssembly

A function may leave several values; the caller uses them in order.

(module
  ;; A function may leave several results on the stack; the caller
  ;; receives them in order.
  (func $divmod (export "divmod") (param $n i32) (param $d i32)
        (result i32 i32)
    (i32.div_s (local.get $n) (local.get $d))
    (i32.rem_s (local.get $n) (local.get $d)))

  ;; The two results feed the next instruction like any operands.
  (func (export "digit_sum_2") (param $n i32) (result i32)
    (call $divmod (local.get $n) (i32.const 10))
    i32.add))

How it works

1. (result i32 i32) types two returns — here quotient and remainder.
2. The body pushes both; nothing more is needed.
3. The caller's i32.add consumes the pair straight off the stack.

Keywords and builtins used here

• call
• export
• func
• i32
• module
• param
• result

The run, in numbers

Lines

12

Characters to type

440

Tokens

84

Three-star pace

65 tpm

At the three-star pace of 65 tokens a minute, this run takes about 78 seconds.

Type this snippet

Step 3 of 3 in Wider types, step 25 of 28 in Language basics.

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