mirror of
https://github.com/golang/go
synced 2024-11-06 08:36:14 -07:00
0b477ef17e
X ,s;^// \$G (\$D/)?\$F\.go *$;// compile;g X ,s;^// \$G (\$D/)?\$F\.go && \$L \$F\.\$A *$;// build;g X ,s;^// \$G (\$D/)?\$F\.go && \$L \$F\.\$A && \./\$A\.out *$;// run;g X ,s;^// errchk \$G( -e)? (\$D/)?\$F\.go *$;// errorcheck;g R=golang-dev, bradfitz CC=golang-dev https://golang.org/cl/5656082
122 lines
2.0 KiB
Go
122 lines
2.0 KiB
Go
// 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.
|
|
|
|
package main
|
|
|
|
import (
|
|
"fmt"
|
|
"runtime"
|
|
"time"
|
|
)
|
|
|
|
type Number struct {
|
|
next *Number
|
|
}
|
|
|
|
// -------------------------------------
|
|
// Peano primitives
|
|
|
|
func zero() *Number { return nil }
|
|
|
|
func is_zero(x *Number) bool { return x == nil }
|
|
|
|
func add1(x *Number) *Number {
|
|
e := new(Number)
|
|
e.next = x
|
|
return e
|
|
}
|
|
|
|
func sub1(x *Number) *Number { return x.next }
|
|
|
|
func add(x, y *Number) *Number {
|
|
if is_zero(y) {
|
|
return x
|
|
}
|
|
|
|
return add(add1(x), sub1(y))
|
|
}
|
|
|
|
func mul(x, y *Number) *Number {
|
|
if is_zero(x) || is_zero(y) {
|
|
return zero()
|
|
}
|
|
|
|
return add(mul(x, sub1(y)), x)
|
|
}
|
|
|
|
func fact(n *Number) *Number {
|
|
if is_zero(n) {
|
|
return add1(zero())
|
|
}
|
|
|
|
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 zero()
|
|
}
|
|
|
|
func count(x *Number) int {
|
|
if is_zero(x) {
|
|
return 0
|
|
}
|
|
|
|
return count(sub1(x)) + 1
|
|
}
|
|
|
|
func check(x *Number, expected int) {
|
|
var c = count(x)
|
|
if c != expected {
|
|
panic(fmt.Sprintf("error: found %d; expected %d", c, expected))
|
|
}
|
|
}
|
|
|
|
// -------------------------------------
|
|
// 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)
|
|
}
|
|
|
|
// -------------------------------------
|
|
// Factorial
|
|
|
|
func main() {
|
|
t0 := time.Now()
|
|
verify()
|
|
for i := 0; i <= 9; i++ {
|
|
print(i, "! = ", count(fact(gen(i))), "\n")
|
|
}
|
|
runtime.GC()
|
|
t1 := time.Now()
|
|
|
|
gcstats("BenchmarkPeano", 1, t1.Sub(t0))
|
|
}
|