PATCH: 4.1: multi-parameter for loop

[Peter Stephenson <pws@xxxxxxx>]

This is meddling with things one probably shouldn't touch, unless one's
working on a particularly annoying and sporadic bug in something else.

This extends the for syntax to take multiple parameters after it; they take
multiple words from the argument list.  The main intended use of this is
for imitating perl's `each' feature:

  typeset -A assoc
  assoc=(key1 val1 key2 val2)
  for key value in ${(kv)assoc}; do
    print $key $value
  done

prints
  
  key1 val1
  key2 val2

(though ordering of elements isn't guaranteed, of course).

My main worry is that the wordcode stuff is as clear as mud to me.  In
particular, I don't know what WC_FOR_SKIP is doing, why it divides the data
size(?) by 4, and whether it needs changing when there's more stuff in
the for structure.

I probably won't be committing this for a while, if at all.  All tests
still pass, though.

Index: Src/loop.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/loop.c,v
retrieving revision 1.4
diff -u -r1.4 loop.c
--- Src/loop.c	2000/06/17 17:05:53	1.4
+++ Src/loop.c	2001/06/20 14:34:48
@@ -52,15 +52,15 @@
     Wordcode end, loop;
     wordcode code = state->pc[-1];
     int iscond = (WC_FOR_TYPE(code) == WC_FOR_COND), ctok = 0, atok = 0;
+    int last = 0;
     char *name, *str, *cond = NULL, *advance = NULL;
     zlong val = 0;
-    LinkList args = NULL;
+    LinkList vars = NULL, args = NULL;
 
-    name = ecgetstr(state, EC_NODUP, NULL);
     end = state->pc + WC_FOR_SKIP(code);
 
     if (iscond) {
-	str = dupstring(name);
+	str = dupstring(ecgetstr(state, EC_NODUP, NULL));
 	singsub(&str);
 	if (isset(XTRACE)) {
 	    char *str2 = dupstring(str);
@@ -77,28 +77,32 @@
 	}
 	cond = ecgetstr(state, EC_NODUP, &ctok);
 	advance = ecgetstr(state, EC_NODUP, &atok);
-    } else if (WC_FOR_TYPE(code) == WC_FOR_LIST) {
-	int htok = 0;
-
-	if (!(args = ecgetlist(state, *state->pc++, EC_DUPTOK, &htok))) {
-	    state->pc = end;
-	    return 0;
-	}
-	if (htok)
-	    execsubst(args);
     } else {
-	char **x;
+	vars = ecgetlist(state, *state->pc++, EC_NODUP, NULL);
+
+	if (WC_FOR_TYPE(code) == WC_FOR_LIST) {
+	    int htok = 0;
+
+	    if (!(args = ecgetlist(state, *state->pc++, EC_DUPTOK, &htok))) {
+		state->pc = end;
+		return 0;
+	    }
+	    if (htok)
+		execsubst(args);
+	} else {
+	    char **x;
 
-	args = newlinklist();
-	for (x = pparams; *x; x++)
-	    addlinknode(args, dupstring(*x));
+	    args = newlinklist();
+	    for (x = pparams; *x; x++)
+		addlinknode(args, dupstring(*x));
+	}
     }
     lastval = 0;
     loops++;
     pushheap();
     cmdpush(CS_FOR);
     loop = state->pc;
-    for (;;) {
+    while (!last) {
 	if (iscond) {
 	    if (ctok) {
 		str = dupstring(cond);
@@ -127,14 +131,29 @@
 	    if (!val)
 		break;
 	} else {
-	    if (!args || !(str = (char *) ugetnode(args)))
-		break;
-	    if (isset(XTRACE)) {
-		printprompt4();
-		fprintf(xtrerr, "%s=%s\n", name, str);
-		fflush(xtrerr);
+	    LinkNode node;
+	    int count = 0;
+	    for (node = firstnode(vars); node; incnode(node))
+	    {
+		name = (char *)getdata(node);
+		if (!args || !(str = (char *) ugetnode(args)))
+		{
+		    if (count) { 
+			str = "";
+			last = 1;
+		    } else
+			break;
+		}
+		if (isset(XTRACE)) {
+		    printprompt4();
+		    fprintf(xtrerr, "%s=%s\n", name, str);
+		    fflush(xtrerr);
+		}
+		setsparam(name, ztrdup(str));
+		count++;
 	    }
-	    setsparam(name, ztrdup(str));
+	    if (!count)
+		break;
 	}
 	state->pc = loop;
 	execlist(state, 1, do_exec && args && empty(args));
Index: Src/parse.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/parse.c,v
retrieving revision 1.23
diff -u -r1.23 parse.c
--- Src/parse.c	2001/06/18 07:34:34	1.23
+++ Src/parse.c	2001/06/20 14:34:49
@@ -903,15 +903,25 @@
 	yylex();
 	type = WC_FOR_COND;
     } else {
+	int np, n, isin = 0;
 	infor = 0;
 	if (tok != STRING || !isident(tokstr))
 	    YYERRORV(oecused);
-	ecstr(tokstr);
+	np = ecadd(0);
+	n = 0;
 	incmdpos = 1;
-	yylex();
-	if (tok == STRING && !strcmp(tokstr, "in")) {
-	    int np, n;
+	for (;;) {
+	    n++;
+	    ecstr(tokstr);
+	    yylex();	
+	    if (tok != STRING || (isin = !strcmp(tokstr, "in")) || sel)
+		break;
+	    if (!isident(tokstr))
+		YYERRORV(oecused);
+	}
+	ecbuf[np] = n;
 
+	if (isin) {
 	    incmdpos = 0;
 	    yylex();
 	    np = ecadd(0);
@@ -921,8 +931,6 @@
 	    ecbuf[np] = n;
 	    type = (sel ? WC_SELECT_LIST : WC_FOR_LIST);
 	} else if (tok == INPAR) {
-	    int np, n;
-
 	    incmdpos = 0;
 	    yylex();
 	    np = ecadd(0);
Index: Doc/Zsh/grammar.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/grammar.yo,v
retrieving revision 1.4
diff -u -r1.4 grammar.yo
--- Doc/Zsh/grammar.yo	2000/08/29 06:35:40	1.4
+++ Doc/Zsh/grammar.yo	2001/06/20 14:34:49
@@ -149,12 +149,20 @@
 findex(for)
 cindex(for loops)
 cindex(loops, for)
-item(tt(for) var(name) [ tt(in) var(word) ... var(term) ] tt(do) var(list) tt(done))(
+item(tt(for) var(name) ... [ tt(in) var(word) ... ] var(term) tt(do) var(list) tt(done))(
 where var(term) is at least one newline or tt(;).
 Expand the list of var(word)s, and set the parameter
 var(name) to each of them in turn, executing
 var(list) each time.  If the tt(in) var(word) is omitted,
 use the positional parameters instead of the var(word)s.
+
+More than one parameter var(name) can appear before the list of
+var(word)s.  If var(N) var(name)s are given, then on each execution of the
+loop the next tt(N) var(word)s are assigned to the corresponding
+parameters.  If there are more var(name)s than remaining var(word)s, the
+remaining parameters are each set to the empty string.  Execution of the
+loop ends when there is no remaining var(word) to assign to the first
+var(name).
 )
 item(tt(for LPAR()LPAR()) [var(expr1)] tt(;) [var(expr2)] tt(;) [var(expr3)] tt(RPAR()RPAR() do) var(list) tt(done))(
 The arithmetic expression var(expr1) is evaluated first (see

-- 
Peter Stephenson <pws@xxxxxxx>                  Software Engineer
CSR Ltd., Unit 300, Science Park, Milton Road,
Cambridge, CB4 0XL, UK                          Tel: +44 (0)1223 392070


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