ref: 577f8a21ded3a49c799ee49b90508801f1361842
dir: /Exceptions/exceptions.b/
implement Exceptions; include "sys.m"; include "draw.m"; sys: Sys; Exceptions: module { init: fn(nil: ref Draw->Context, nil: list of string); }; FIB: exception(int, int); init(nil: ref Draw->Context, nil: list of string) { sys = load Sys Sys->PATH; for(i := 0; i < 5 ; i++) { f := fibonacci(i); if(f < 0) break; sys->print("F(%d) = %d\n", i, f); } raise "going down!"; exit; } fibonacci(n: int): int { { fib(1, n, 1, 1); } exception e { FIB => (x, nil) := e; return x; "*" => sys->print("unexpected string exception %s raised\n", e); * => sys->print("unexpected exception raised\n"); } return 0; } fib(n, m, x, y: int) raises (FIB) { if(n >= m) raise FIB(x, y); { fib(n+1, m, x, y); } exception e { FIB => (x, y) = e; x = x+y; y = x-y; raise FIB(x, y); } }