system.io

Input/Output operations for console and standard streams.

import system.io as io

Output Functions

println(value)

Print a value followed by a newline.

io.println("Hello, World!")
io.println(42)
io.println([1, 2, 3])

print(value)

Print a value without a trailing newline.

io.print("Enter your name: ")
let name = io.readLine()
io.println("Hello, " + name)

printf(format, ...args)

Formatted output (C-style format string).

io.printf("Name: %s, Age: %d\n", "Alice", 30)
io.printf("Pi: %.2f\n", 3.14159)
io.printf("Hex: %x\n", 255)

Format specifiers:

Input Functions

readLine()

Read a line of text from standard input.

io.print("What is your name? ")
let name = io.readLine()
io.println("Hello, " + name + "!")

readInt()

Read and parse an integer from standard input.

io.print("Enter a number: ")
let num = io.readInt()
io.println("You entered: " + num)

readDouble()

Read and parse a floating-point number.

io.print("Enter a decimal: ")
let value = io.readDouble()
io.println("You entered: " + value)

readChar()

Read a single character.

io.print("Press any key: ")
let ch = io.readChar()
io.println("You pressed: " + ch)

Error Output

eprintln(value)

Print to standard error with newline.

io.eprintln("Error: File not found")

eprint(value)

Print to standard error without newline.

io.eprint("Warning: ")
io.eprintln("Low memory")

Stream Control

flush()

Flush standard output buffer.

io.print("Processing...")
io.flush()  // Ensure output appears immediately
// ... do work ...
io.println(" done!")

Complete Examples

Interactive Calculator

import system.io as io

io.println("Simple Calculator")
io.println("Enter two numbers:")

io.print("First number: ")
let a = io.readInt()

io.print("Second number: ")
let b = io.readInt()

io.println("")
io.println("Results:")
io.printf("  %d + %d = %d\n", a, b, a + b)
io.printf("  %d - %d = %d\n", a, b, a - b)
io.printf("  %d * %d = %d\n", a, b, a * b)
io.printf("  %d / %d = %.2f\n", a, b, a / b)

Menu System

import system.io as io

fn showMenu() {
io.println("\n=== Menu ===")
io.println("1. Option One")
io.println("2. Option Two")
io.println("3. Exit")
io.print("Choice: ")
return io.readLine()
}

let running = true
while (running) {
let choice = showMenu()

if (choice == "1") {
io.println("You chose Option One")
} else if (choice == "2") {
io.println("You chose Option Two")
} else if (choice == "3") {
running = false
io.println("Goodbye!")
} else {
io.eprintln("Invalid choice!")
}
}

Progress Indicator

import system.io as io
import system.time as time

fn showProgress(current, total) {
let percent = (current * 100) / total
io.printf("\rProgress: [%d/%d] %d%%", current, total, percent)
io.flush()
}

io.println("Processing...")
for (let i = 1; i <= 10; i = i + 1) {
time.sleep(100)  // Simulate work
showProgress(i, 10)
}
io.println("\nDone!")

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