From: Russ Cox <rsc@golang.org>
Date: Fri, 20 Mar 2009 18:32:58 +0000 (-0700)
Subject: range over channels.
X-Git-Tag: weekly.2009-11-06~1998
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=54aa835b44cf62fa503edb174f507a6331da8b7a;p=gostls13.git

range over channels.

also fix multiple-evaluation bug in range over arrays.

R=ken
OCL=26576
CL=26576
---

diff --git a/src/cmd/gc/walk.c b/src/cmd/gc/walk.c
index c5442fe76e..a510a1a989 100644
--- a/src/cmd/gc/walk.c
+++ b/src/cmd/gc/walk.c
@@ -3184,7 +3184,7 @@ Node*
 dorange(Node *nn)
 {
 	Node *k, *v, *m;
-	Node *n, *hk, *on, *r, *a;
+	Node *n, *hv, *hc, *ha, *hk, *on, *r, *a;
 	Type *t, *th;
 	int local;
 
@@ -3212,16 +3212,23 @@ dorange(Node *nn)
 		goto ary;
 	if(t->etype == TMAP)
 		goto map;
+	if(t->etype == TCHAN)
+		goto chan;
 
 	yyerror("range must be over map/array");
 	goto out;
 
 ary:
 	hk = nod(OXXX, N, N);		// hidden key
-	tempname(hk, types[TINT]);	// maybe TINT32
+	tempname(hk, types[TINT]);
+	
+	ha = nod(OXXX, N, N);		// hidden array
+	tempname(ha, t);
 
 	n->ninit = nod(OAS, hk, nodintconst(0));
-	n->ntest = nod(OLT, hk, nod(OLEN, m, N));
+	n->ninit = list(nod(OAS, ha, m), n->ninit);
+
+	n->ntest = nod(OLT, hk, nod(OLEN, ha, N));
 	n->nincr = nod(OASOP, hk, nodintconst(1));
 	n->nincr->etype = OADD;
 
@@ -3233,7 +3240,7 @@ ary:
 		if(local)
 			v = old2new(v, t->type);
 		n->nbody = list(n->nbody,
-			nod(OAS, v, nod(OINDEX, m, hk)) );
+			nod(OAS, v, nod(OINDEX, ha, hk)) );
 	}
 	addtotop(n);
 	goto out;
@@ -3288,7 +3295,29 @@ map:
 	r = nod(OADDR, hk, N);
 	r = nod(OCALL, on, r);
 	n->nbody = nod(OAS, nod(OLIST, k, v), r);
+	goto out;
+
+chan:
+	if(v != N)
+		yyerror("chan range can only have one variable");
+
+	hc = nod(OXXX, N, N);	// hidden chan
+	tempname(hc, t);
+	
+	hv = nod(OXXX, N, N);	// hidden value
+	tempname(hv, t->type);
 
+	n->ninit = list(
+		nod(OAS, hc, m),
+		nod(OAS, hv, nod(ORECV, hc, N))
+	);
+	n->ntest = nod(ONOT, nod(OCLOSED, hc, N), N);
+	n->nincr = nod(OAS, hv, nod(ORECV, hc, N));
+
+	if(local)
+		k = old2new(k, hv->type);
+	n->nbody = nod(OAS, k, hv);
+	addtotop(n);
 	goto out;
 
 out:
diff --git a/test/chan/sieve.go b/test/chan/sieve.go
index 0cebdc6412..7d06e98fa7 100644
--- a/test/chan/sieve.go
+++ b/test/chan/sieve.go
@@ -19,8 +19,7 @@ func Generate(ch chan<- int) {
 // Copy the values from channel 'in' to channel 'out',
 // removing those divisible by 'prime'.
 func Filter(in <-chan int, out chan<- int, prime int) {
-	for {
-		i := <-in;  // Receive value of new variable 'i' from 'in'.
+	for i := range in {  // Loop over values received from 'in'.
 		if i % prime != 0 {
 			out <- i  // Send 'i' to channel 'out'.
 		}
@@ -32,6 +31,7 @@ func Sieve(primes chan<- int) {
 	ch := make(chan int);  // Create a new channel.
 	go Generate(ch);  // Start Generate() as a subprocess.
 	for {
+		// Note that ch is different on each iteration.
 		prime := <-ch;
 		primes <- prime;
 		ch1 := make(chan int);
@@ -45,7 +45,7 @@ func main() {
 	go Sieve(primes);
 	a := []int{2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97};
 	for i := 0; i < len(a); i++ {
-		if <-primes != a[i] { panic(a[i])}
+		if x := <-primes; x != a[i] { panic(x, " != ", a[i]) }
 	}
 	sys.Exit(0);
 }
diff --git a/test/range.go b/test/range.go
new file mode 100644
index 0000000000..7a8c686350
--- /dev/null
+++ b/test/range.go
@@ -0,0 +1,59 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// 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
+
+// test range over channels
+
+func gen(c chan int, lo, hi int) {
+	for i := lo; i <= hi; i++ {
+		c <- i;
+	}
+	close(c);
+}
+
+func seq(lo, hi int) chan int {
+	c := make(chan int);
+	go gen(c, lo, hi);
+	return c;
+}
+
+func testchan() {
+	s := "";
+	for i := range seq('a', 'z') {
+		s += string(i);
+	}
+	if s != "abcdefghijklmnopqrstuvwxyz" {
+		panicln("Wanted lowercase alphabet; got", s);
+	}
+}
+
+// test that range over array only evaluates
+// the expression after "range" once.
+
+var nmake = 0;
+func makearray() []int {
+	nmake++;
+	return []int{1,2,3,4,5};
+}
+
+func testarray() {
+	s := 0;
+	for k, v := range makearray() {
+		s += v;
+	}
+	if nmake != 1 {
+		panicln("range called makearray", nmake, "times");
+	}
+	if s != 15 {
+		panicln("wrong sum ranging over makearray");
+	}
+}
+
+func main() {
+	testchan();
+	testarray();
+}