@tt: translate-time programs

@tt runs a program before C is emitted. It can compute, read files, and emit any C text or tokens.

A computed table

NanoC

@tt
  f square(n) = n * n
  values := []
  for i range(5)
    values = push(values, str(square(i)))
  emit("static const int squares[] = {" + join(values, ",") + "};")
f main
  squares[4] != 16

static const int squares[] = {0,1,4,9,16};

int main(void) {
    return squares[4] != 16;
}

Values are dynamic: integers, text, lists and booleans. Functions, loops and branches use the same indentation syntax as NanoC itself.

Quoting code

quote(...) captures tokens with $name holes, so you can generate declarations without string concatenation.

NanoC

@tt
  n := 42
  emit(quote(int answer = $n;))
f main
  answer != 42

int answer = 42;

int main(void) {
    return answer != 42;
}

Context functions

Function	Returns
`cycle()`	Current one-based expansion cycle
`line()`	Source line of the call
`file()`	Input file spelling
`name()`	Enclosing function name, or empty at file scope
`target()`	Selected C standard, or `c++17`

Source transforms

rewrite(text) replaces the source and the pipeline repeats until the text stops changing; again() forces another pass. Counts are bounded by default; --max-passes 0 --max-steps 0 removes the limits.

Host effects

Native @tt can read and write files and run programs (write, mkdir, remove, run, exec, sh). --check validates expansion but refuses to execute those, so checking never changes your machine.

Every builtin has a reference page with a verified example.
The guide lesson walks through the pipeline.