Console I/O and formatting

I/O statements

print, println, and input are Wave language statements for formatted console I/O.

fun main() {
    var count: i32 = 0;
    input("{}", count);
    print("count = ");
    println("{}", count);
}

Each statement ends with ;. The first argument must be a string literal; a variable or computed string cannot be used as the format argument.

Placeholders

Only the exact two-character sequence {} is a placeholder.

println("name = {}, score = {}", name, score);

The number of placeholders must equal the number of following expressions. A mismatch is a compile-time error.

println("{} {}", one);       // error: two placeholders, one value
println("plain text", one); // error: no placeholder, extra value

Other braces remain literal text; there are no named or indexed placeholders in this syntax.

print and println

print writes the formatted text as-is. println appends a newline.

print("loading...");
println("done");

Formatting accepts scalar values such as integers, floating-point values, strings, and pointers. Arrays and structs are not formatting arguments.

input destinations

Every expression after the input format must identify writable storage for the parsed value.

var number: i32 = 0;
input("{}", number);

Variables, supported field accesses, and supported dereference forms can be destinations. Literals and computed rvalues cannot.

If input cannot convert every requested value, the program exits with a failure status.

Runtime boundary

These console statements require a hosted runtime. Freestanding kernels and embedded programs provide target-specific input and output through explicit functions or FFI boundaries.