eqz: Wasm numeric instruction

The eqz numeric instruction checks if a number is equal to zero.

Try it

(module
  (import "env" "log_bool" (func $log_bool (param i32)))
  (func $main
    ;; load `0` onto the stack
    i32.const 0

    i32.eqz ;; check if the previous number on the stack is equal to 0
    call $log_bool ;; log the result
  )
  (start $main)
)

const url = "{%wasm-url%}";

function log_bool(value) {
  console.log(Boolean(value));
  // Expected output: false
}

await WebAssembly.instantiateStreaming(fetch(url), {
  env: { log_bool },
});

Syntax

value_type.eqz

value_type

The type of value the instruction is being run on. The following types support eqz:

• i32
• i64

eqz

The eqz instruction. Must always be included after the value_type and a period (.).

Type

[input] -> [output]

input

The input value.

output

The output value. If input is equal to 0, 1 will be pushed on to the stack, otherwise 0 will be pushed on to the stack. The output values are integers.

Binary encoding

Specifications

• WebAssembly Core Specification

See also

• eq