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Printing and I/O

esque's I/O surface is intentionally tiny. There are three functions you can call for their side effect, plus one expression form (each) that drives them across a tensor. Every I/O-performing function — the intrinsics and any wrappers you write — must be marked @io (see Effects and I/O).

print_i32(x: i32) -> i32 @io​

Writes x to standard output as a decimal integer, followed by a newline. Returns x unchanged so the call can sit in expression position.

@io fn main() -> i32 = print_i32(42)
$ ./hello
42
$ echo $?
42

print_i32 is a runtime intrinsic, synthesised by the compiler when the program references it. It uses the Linux write syscall directly; there is no libc dependency.

print_f32(x: f32) -> f32 @io​

Writes x as a decimal float (six fractional digits, no trailing trim today), followed by a newline. Returns x unchanged.

@io fn main() -> i32 = { print_f32(3.14); 0 }
$ ./hello
3.140000
$ echo $?
0

print_str(s: string) -> string @io​

Writes the bytes of s verbatim. No trailing newline is added. Returns s unchanged.

@io fn main() -> i32 = { print_str("hello\n"); 0 }

each(v, f)​

Drive a print across a tensor:

@io fn main() -> i32 = {
    each(0..5, print_i32);
    0
}
$ ./prog
0
1
2
3
4
$ echo $?
0

each accepts any named top-level function whose effect set fits the enclosing function's. A pure f works in any caller; an @io f requires the caller to be @io too. You can wrap your own print logic:

@io fn shout(x: i32) -> i32 = print_i32(x * 100)

@io fn main() -> i32 = {
    each(0..3, shout);
    0
}

A closure or captured name is still a type error — f must resolve to a top-level function name.

What is missing​

  • Reading input. There is no read_line, no argv, no stdin.
  • File I/O.
  • Environment / clock / RNG.

These are stdlib gaps, not language gaps. Once we settle on a runtime story for them they will appear as ordinary @io functions.

Reading input​

There is no input today. Write programs whose inputs are baked in or computed; treat the exit code or stdout as the output.

Next: Worked examples​