source: doc/papers/concurrency/examples/Fib.cfa @ 830edc6

#include <thread.hfa>
#include <fstream.hfa>

int fn1, fn2, state = 1;
int fib_gvar() {
        int fn;
        choose ( state ) {
          case 1: fn = 0;  fn1 = fn;  state = 2;
          case 2: fn = 1;  fn2 = fn1;  fn1 = fn;  state = 3;
          case 3: fn = fn1 + fn2;  fn2 = fn1;  fn1 = fn;
        }
        return fn;
}

#define FibCtor { 1, 0 }
typedef struct { int fn1, fn; } Fib;
int fib_state( Fib & f ) with(f) {
        int ret = fn; fn = fn1; fn1 = fn + ret;
        return ret;
}

coroutine Fib1 { int fn; };                                             // used for communication
void main( Fib1 & fib ) with( fib ) {                   // called on first resume
        fn = 0;  int fn1 = fn; suspend();
        fn = 1;  int fn2 = fn1;  fn1 = fn; suspend();
        for () {
                fn = fn1 + fn2;  fn2 = fn1;  fn1 = fn; suspend();
        }
}
int ?()( Fib1 & fib ) with( fib ) { return resume( fib ).fn; }

coroutine Fib2 { int fn; };                                             // used for communication
void main( Fib2 & fib ) with( fib ) {                   // called on first resume
        int fn1;                                                                        // precompute first two states
        [fn1, fn] = [1, 0];
        for () {
                suspend();                                                              // restart last resume
                [fn1, fn] = [fn, fn + fn1];
        }
}
int ?()( Fib2 & fib ) {                                                 // function-call interface
        return resume( fib ).fn;                                        // restart last suspend
}
int ?()( Fib2 & fib, int N ) {                                  // skip N values
        for ( N - 1 ) fib();                                            // use function-call interface
        return fib();
}
double ?()( Fib2 & fib ) {                                              // different return type
        return (int)(fib()) / 3.14159;                          // cast prevents recursive call
}

int main() {
        for ( 10 )
                sout | fib_gvar();
        sout | nl;

        Fib f1 = FibCtor, f2 = FibCtor;
        for ( 10 )
                sout | fib_state( f1 ) | fib_state( f2 );
        sout | nl;

        Fib1 f1, f2;
        for ( 10 )
                sout | f1() | f2();
        sout | nl;

        Fib2 f12, f22;
        for ( 10 )
                sout | (int)f12() | (double)f12() | f22( 2 );
}

// Local Variables: //
// tab-width: 4 //
// fill-column: 120 //
// compile-command: "cfa Fib.cfa" //
// End: //