source: doc/papers/concurrency/examples/Fib.cfa@ 043a5b6

#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 FIB_INIT { 0, 1 }
typedef struct { int fn1, fn2; } Fib;
int fib_state( Fib & f ) with( f ) {
        int ret = fn2;
        int fn = fn1 + fn2;
        fn2 = fn1; fn1 = fn;
        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 next( Fib1 & fib ) with( fib ) { resume( fib ); return fn; }

coroutine Fib2 { int ret; };                                    // used for communication
void main( Fib2 & fib ) with( fib ) {                   // called on first resume
        int fn, fn1 = 1, fn2 = 0;                                       // precompute first two states
        for () {
                ret = fn2;
                fn = fn1 + fn2;  fn2 = fn1;  fn1 = fn;  // general case
                suspend();                                                              // restart last resume
        }
}
int next( Fib2 & fib ) with( fib ) {
        resume( fib );                                                          // restart last suspend
        return ret;
}

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

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

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

        Fib2 f1, f2;
        for ( 10 )
                sout | next( (Fib2 &)f1 ) | next( (Fib2 &)f2 );
}

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