Intrinsic Constants

Alongside the constants you declare, the compiler provides a small set of intrinsic constants, each written with a leading #. They are not declared anywhere — the compiler substitutes each one with information about the source location or the build at the exact point where it appears.

Print(#file);   // e.g. "Main.rux"
Print(#line);   // the line number of this call

Available Intrinsics

Constant	Type	Expands to
#module	char8[]	Name of the enclosing module
#file	char8[]	Path of the current source file
#function	char8[]	Name of the enclosing function
#line	uint	Current line number
#column	uint	Current column number
#date	char8[]	Date the program was compiled
#time	char8[]	Time the program was compiled

The string-valued intrinsics produce a char8[]; #line and #column produce a compile-time unsigned integer that fits wherever an unsigned type such as uint32 or uint is expected.

Substitution at the Point of Use

An intrinsic expands where it is written. #line on line 40 evaluates to 40; #function inside func Parse evaluates to "Parse". Because the value is fixed at compile time, using one costs nothing at run time — it is already a plain literal by the time the program runs.

Default Arguments for Diagnostics

The most important use is as a default argument value. When an intrinsic is the default for a parameter, it expands at the call site rather than where the function is defined — so the function automatically learns where it was called from. This is exactly how the standard library's Assert and Fatal capture a location without the caller passing one:

func Log(message: char8[],
         file: char8[] = #file,
         function: char8[] = #function,
         line: uint32 = #line) {
    Print(file, ":", line, " (", function, ") ", message);
}

Log("starting up");   // file, function, and line filled in from this call site

Callers normally omit these arguments and let the compiler fill them in; pass them explicitly only to forward a location from somewhere else.

Build Stamps

Because #date and #time are constant expressions, they can initialize a regular const, which is a convenient way to embed a build stamp:

const BuildDate: char8[] = #date;
const BuildTime: char8[] = #time;

See Also

• Constants — declaring your own compile-time constants
• Assert and Fatal — standard-library functions that use these intrinsics
• String Literals — the char8[] type the string intrinsics produce