It is possible to transform the pure Rosetta form of GNU nested function similar to the pure C, such that it doesn't need any stack trampoline. I wonder if that would be closer in performance to the pure C form.
(I can't be bothered to run his benchmarks)
#include <stdio.h>
typedef struct env_ E;
typedef struct fat_ptr_ Fp;
typedef int fn(E*);
struct fat_ptr_ {
fn *f;
E *e;
};
#define INT(body) ({ int lambda(E*){ return body; }; (Fp){lambda,0}; })
struct env_ {
int k;
Fp xl; Fp x2; Fp x3; Fp x4;
};
#define FpMk(fn,e) {fn, e}
#define FpCall(fn) (fn.f(fn.e))
int main(){
int a(E env, Fp x5){
int b(E *ep){
return a( (E){--(ep->k), FpMk(b, ep), ep->xl, ep->x2, ep->x3}, ep->x4 );
}
return env.k<=0 ? FpCall(env.x4) + FpCall(x5) : b(&env);
}
printf(" %d\n", a( (E){10, INT(1), INT(-1), INT(-1), INT(1)}, INT(0)) );
}