Macro proposal

macro.c

// 1. Macros with arguments
macro @foo(int &v) {
  v++;
  if (v > 10) return 10;
  return v;
}

int bar() {
  int a = 10;
  @foo(a);
}

// Expands to:
/*
int bar() {
  int a = 10;
  a++;
  if (a > 10) return 10;
  return a;
}
*/

// 2. macros may return values
macro int @foo2(int &v, int &w) {
  v++;
  if (v > 10) return 10;
  w += 3;
  return 0;
}

int bar2() {
  d = 0;
  a = 10;
  int b = @foo2(a, d);
}

// Expands to
/*
void bar2() {
  d = 0;
  a = 10;
  int b;
  if (a > 10) {
    b = 10;
  } else {
    b = 0;
    d += 3;
  }  
}  
*/

// 3. They can include a single body that is expanded inline
macro int @foo3(int &a, @block body) {
  while (a > 10) {
    a--;
    @body();
  }
}

void bar3() {
  b = 20;
  @foo3(b) {
    print(b);
  }
}

// Expands to:
/*
void bar3() {
  b = 20;
  while (b > 10) {
    b--;
    {
      print(b);
    }  
  }
}
*/

// 4. The body itself may take an arbitrary number of injected parameters
macro int @foo4(@block(int x, int y) body) {
  for (int i = 0; i < 100; i++) {
    @body(i, i % 3);
  }
}

void bar4() {
  @foo4() {
    if (@y == 0) print(@x);
  }
}

// Expands to:
/*
void bar4() {
  for (int i = 0; i < 100; i++) {
    if (i % 3 == 0) print (i);
  }
}
*/

// 5. Untyped is just fine:
macro @foo5(&v) {
  v *= 2;
}

int bar5() {
  int a = 10;
  @foo5(a); // Valid, becomes a *= 2;
  float b = 1.2;
  @foo5(b); // Valid, becomes b *= 2;
}