Formatted Output with iodine

Use iodine’s printd library to write formatted output from i++ programs.

The iodine/printd.ih library provides printd, a C-style formatted output function that writes to standard output and appends a newline.

Print a value

Pass a format string and values, such as printd("count: %d", count).

One call, one line

printd appends a newline after each call.

Import printd

Import printd from iodine. Choose whether to expose the function or retain an explicit namespace qualifier.

Expose printd

After expose printd, call the function directly:

using printd from <iodine/printd>;
expose printd;

int main() {
    printd("Hello, i++!");
    printd("value: %d", 42);
    return 0;
}

Use the namespace

Without expose, qualify each call with @lib:

using printd from <iodine/printd>;

int main() {
    printd@lib("Hello, i++!");
    printd@lib("value: %d", 42);
    return 0;
}

For namespace syntax and other import forms, see library imports.

Supported format specifiers

The library handles common C-style format tokens:

Specifier	Value
%d, %i	int
%ld	long
%lld	long long
%u	Unsigned integer
%o	Octal
%x, %X	Lowercase or uppercase hexadecimal
%p	Pointer
%s	String
%c	Character
%f	Floating-point value
%%	Literal percent sign

Pass values after the format string, as you would with C’s printf. For example:

printd("%s scored %d points", "Ada", 100);

printfs and its interpolation syntax are not included in this iodine library. Use printd with format specifiers.

The implementation writes through the Linux x86_64 write system call. Its sys_write assembly function is defined inside printd.ih.