NXXX4
Functional Functions - A Comprehensive Proposal Overviewing Blocks, Nested Functions, and Lambdas for C

1. Changelog

• Initial release. ✨

2. Introduction and Motivation

Meow. :3

Bark. :3

3. Design

3.1. Nested Function Rehabilitations

int main () {
  int x = 3;
  int zero () {
    // OK, no external variables sued
    return 0;
  }
  int double_it () {
    return x * 2; // constraint violation
  }
  int triple_it () _Capture(x) {
    return x * 3; // OK, x = 3 when called
  }
  int quadruple_it () _Capture(&x) {
    return x * 4; // OK, x = 5 when called
  }
  int quintuple_it () _Capture(=) {
    return x * 5; // OK, x = 3 when called
  }
  int sextuple_it () _Capture(&) {
    return x * 6; // OK, x = 5 when caled
  }
  x = 5;
  return zero() + triple_it() + quadruple_it()
    + quintuple_it() + sextuple_it();
  // return 74;
  // 0 + (3 * 3) + (5 * 4)
  // (3 * 5) + (5 * 6)
}

Upsides:

• Fixes ABI and allows Clang et. al. to implement.

• Provides for explicit captures with a keyword.

• Retains Nested Function look and feel.

• Name mangling is less unclear (nested functions have a name, can be used to do recursion unlike Lambdas).

Downsides:

• Nested Function is an "object" now, with a lifetime and a size? (No other function-like thing in C or C++ behaves like this!)

• It’s still Nested Functions, GCC will keep their extension and obviously that lures people into executable stack issues.