-// $G $F.go && $L $F.$A && ./$A.out
+// run
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+// Test that heavy recursion works. Simple torture test for
+// segmented stacks: do math in unary by recursion.
+
package main
-type Number struct {
- next *Number
-}
+import "runtime"
+type Number *Number
// -------------------------------------
// Peano primitives
func zero() *Number {
- return nil;
+ return nil
}
-
func is_zero(x *Number) bool {
- return x == nil;
+ return x == nil
}
-
func add1(x *Number) *Number {
- e := new(Number);
- e.next = x;
- return e;
+ e := new(Number)
+ *e = x
+ return e
}
-
func sub1(x *Number) *Number {
- return x.next;
+ return *x
}
-
-func add(x, y *Number) *Number{
+func add(x, y *Number) *Number {
if is_zero(y) {
- return x;
+ return x
}
- return add(add1(x), sub1(y));
+ return add(add1(x), sub1(y))
}
-
func mul(x, y *Number) *Number {
- if is_zero(x) || is_zero(y){
- return zero();
+ if is_zero(x) || is_zero(y) {
+ return zero()
}
- return add(mul(x, sub1(y)), x);
+ return add(mul(x, sub1(y)), x)
}
-
func fact(n *Number) *Number {
if is_zero(n) {
- return add1(zero());
+ return add1(zero())
}
- return mul(fact(sub1(n)), n);
+ return mul(fact(sub1(n)), n)
}
-
// -------------------------------------
// Helpers to generate/count Peano integers
func gen(n int) *Number {
if n > 0 {
- return add1(gen(n - 1));
+ return add1(gen(n - 1))
}
- return zero();
+ return zero()
}
-
func count(x *Number) int {
if is_zero(x) {
- return 0;
+ return 0
}
- return count(sub1(x)) + 1;
+ return count(sub1(x)) + 1
}
-
func check(x *Number, expected int) {
- var c = count(x);
+ var c = count(x)
if c != expected {
- panic("error: found ", c, "; expected ", expected, "\n");
+ print("error: found ", c, "; expected ", expected, "\n")
+ panic("fail")
}
}
-
// -------------------------------------
// Test basic functionality
-func verify() {
- check(zero(), 0);
- check(add1(zero()), 1);
- check(gen(10), 10);
-
- check(add(gen(3), zero()), 3);
- check(add(zero(), gen(4)), 4);
- check(add(gen(3), gen(4)), 7);
-
- check(mul(zero(), zero()), 0);
- check(mul(gen(3), zero()), 0);
- check(mul(zero(), gen(4)), 0);
- check(mul(gen(3), add1(zero())), 3);
- check(mul(add1(zero()), gen(4)), 4);
- check(mul(gen(3), gen(4)), 12);
-
- check(fact(zero()), 1);
- check(fact(add1(zero())), 1);
- check(fact(gen(5)), 120);
+func init() {
+ check(zero(), 0)
+ check(add1(zero()), 1)
+ check(gen(10), 10)
+
+ check(add(gen(3), zero()), 3)
+ check(add(zero(), gen(4)), 4)
+ check(add(gen(3), gen(4)), 7)
+
+ check(mul(zero(), zero()), 0)
+ check(mul(gen(3), zero()), 0)
+ check(mul(zero(), gen(4)), 0)
+ check(mul(gen(3), add1(zero())), 3)
+ check(mul(add1(zero()), gen(4)), 4)
+ check(mul(gen(3), gen(4)), 12)
+
+ check(fact(zero()), 1)
+ check(fact(add1(zero())), 1)
+ check(fact(gen(5)), 120)
}
-
// -------------------------------------
// Factorial
+var results = [...]int{
+ 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800,
+ 39916800, 479001600,
+}
func main() {
-
- verify();
- for i := 0; i <= 10; i++ {
- print(i, "! = ", count(fact(gen(i))), "\n");
+ max := 9
+ if runtime.GOARCH == "wasm" {
+ max = 7 // stack size is limited
+ }
+ for i := 0; i <= max; i++ {
+ if f := count(fact(gen(i))); f != results[i] {
+ println("FAIL:", i, "!:", f, "!=", results[i])
+ panic(0)
+ }
}
}
-