std/io

std/io provides functions for writing to stdout/stderr and reading from stdin.

Many of these functions are also available without an import via std/prelude — println and printInt work out of the box in most programs.

API

pub ext fun println(s: String) Void;
pub ext fun printInt(i: Int) Void;
pub ext fun printFloat(f: Float) Void;
pub ext fun printFloat64(f: Float64) Void;
pub ext fun printBool(b: Bool) Void;
pub ext fun printChar(c: Char) Void;
pub ext fun eprintln(s: String) Void;
pub ext fun getLn() String;
pub ext fun printf(format: String, ...) Int;
pub ext fun printfln(format: String, ...) Int;

Function	Description
println(s)	Print a string followed by a newline
printInt(i)	Print an integer
printFloat(f)	Print a float
printFloat64(f)	Print a 64-bit float
printBool(b)	Print true or false
printChar(c)	Print a single character
eprintln(s)	Print to stderr followed by a newline
getLn()	Read a line from stdin (returns String)
printf(fmt, ...)	C-style formatted print (no newline)
printfln(fmt, ...)	C-style formatted print with newline

Examples

Basic output

import "std/io" { println, printInt, printFloat, printBool, printChar };

fun main() Int {
    println("Hello, Zap!");
    printInt(42);
    printFloat(3.14);
    printBool(true);
    printChar('Z');
    return 0;
}

Formatted output

import "std/io";

fun main() Int {
    io.printfln("Name: %s, Age: %d", "Alice", 30);
    io.printfln("Pi ≈ %.4f", 3.14159);
    io.printf("no newline here");
    io.println("");
    return 0;
}

Reading input

import "std/io" { println, getLn };

fun main() Int {
    println("What's your name?");
    var name: String = getLn();
    println("Hello, " ~ name ~ "!");
    return 0;
}

Writing to stderr

import "std/io" { eprintln, println };

fun main() Int {
    println("This goes to stdout");
    eprintln("This goes to stderr");
    return 0;
}