SF patch #872326: Generator expression implementation

(Code contributed by Jiwon Seo.)

The documentation portion of the patch is being re-worked and will be
checked-in soon.  Likewise, PEP 289 will be updated to reflect Guido's
rationale for the design decisions on binding behavior (as described in
in his patch comments and in discussions on python-dev).

The test file, test_genexps.py, is written in doctest format and is
meant to exercise all aspects of the the patch.  Further additions are
welcome from everyone.  Please stress test this new feature as much as
possible before the alpha release.

Modules/parsermodule.c

@@ -855,7 +855,9 @@ VALIDATER(subscriptlist);       VALIDATER(sliceop);
 VALIDATER(exprlist);            VALIDATER(dictmaker);
 VALIDATER(arglist);             VALIDATER(argument);
 VALIDATER(listmaker);           VALIDATER(yield_stmt);
-VALIDATER(testlist1);
+VALIDATER(testlist1);           VALIDATER(gen_for);
+VALIDATER(gen_iter);            VALIDATER(gen_if);
+VALIDATER(testlist_gexp);
 
 #undef VALIDATER
 
@@ -1246,6 +1248,21 @@ validate_list_iter(node *tree)
     return res;
 }
 
+/*  gen_iter:  gen_for | gen_if
+ */
+static int
+validate_gen_iter(node *tree)
+{
+    int res = (validate_ntype(tree, gen_iter)
+               && validate_numnodes(tree, 1, "gen_iter"));
+    if (res && TYPE(CHILD(tree, 0)) == gen_for)
+        res = validate_gen_for(CHILD(tree, 0));
+    else
+        res = validate_gen_if(CHILD(tree, 0));
+
+    return res;
+}
+
 /*  list_for:  'for' exprlist 'in' testlist [list_iter]
  */
 static int
@@ -1268,6 +1285,28 @@ validate_list_for(node *tree)
     return res;
 }
 
+/*  gen_for:  'for' exprlist 'in' test [gen_iter]
+ */
+static int
+validate_gen_for(node *tree)
+{
+    int nch = NCH(tree);
+    int res;
+
+    if (nch == 5)
+        res = validate_gen_iter(CHILD(tree, 4));
+    else
+        res = validate_numnodes(tree, 4, "gen_for");
+
+    if (res)
+        res = (validate_name(CHILD(tree, 0), "for")
+               && validate_exprlist(CHILD(tree, 1))
+               && validate_name(CHILD(tree, 2), "in")
+               && validate_test(CHILD(tree, 3)));
+
+    return res;
+}
+
 /*  list_if:  'if' test [list_iter]
  */
 static int
@@ -1288,6 +1327,25 @@ validate_list_if(node *tree)
     return res;
 }
 
+/*  gen_if:  'if' test [gen_iter]
+ */
+static int
+validate_gen_if(node *tree)
+{
+    int nch = NCH(tree);
+    int res;
+
+    if (nch == 3)
+        res = validate_gen_iter(CHILD(tree, 2));
+    else
+        res = validate_numnodes(tree, 2, "gen_if");
+    
+    if (res)
+        res = (validate_name(CHILD(tree, 0), "if")
+               && validate_test(CHILD(tree, 1)));
+
+    return res;
+}
 
 /*  validate_fpdef()
  *
@@ -2187,7 +2245,7 @@ validate_atom(node *tree)
                    && (validate_rparen(CHILD(tree, nch - 1))));
 
             if (res && (nch == 3))
-                res = validate_testlist(CHILD(tree, 1));
+                res = validate_testlist_gexp(CHILD(tree, 1));
             break;
           case LSQB:
             if (nch == 2)
@@ -2244,7 +2302,7 @@ validate_listmaker(node *tree)
         ok = validate_test(CHILD(tree, 0));
 
     /*
-     *  list_iter | (',' test)* [',']
+     *  list_for | (',' test)* [',']
      */
     if (nch == 2 && TYPE(CHILD(tree, 1)) == list_for)
         ok = validate_list_for(CHILD(tree, 1));
@@ -2266,6 +2324,43 @@ validate_listmaker(node *tree)
     return ok;
 }
 
+/*  testlist_gexp:
+ *    test ( gen_for | (',' test)* [','] )
+ */
+static int
+validate_testlist_gexp(node *tree)
+{
+    int nch = NCH(tree);
+    int ok = nch;
+
+    if (nch == 0)
+        err_string("missing child nodes of testlist_gexp");
+    else {
+        ok = validate_test(CHILD(tree, 0));
+    }
+
+    /*
+     *  gen_for | (',' test)* [',']
+     */
+    if (nch == 2 && TYPE(CHILD(tree, 1)) == gen_for)
+        ok = validate_gen_for(CHILD(tree, 1));
+    else {
+        /*  (',' test)* [',']  */
+        int i = 1;
+        while (ok && nch - i >= 2) {
+            ok = (validate_comma(CHILD(tree, i))
+                  && validate_test(CHILD(tree, i+1)));
+            i += 2;
+        }
+        if (ok && i == nch-1)
+            ok = validate_comma(CHILD(tree, i));
+        else if (i != nch) {
+            ok = 0;
+            err_string("illegal trailing nodes for testlist_gexp");
+        }
+    }
+    return ok;
+}
 
 /*  funcdef:
  *      'def' NAME parameters ':' suite
@@ -2318,6 +2413,18 @@ validate_arglist(node *tree)
         /* raise the right error from having an invalid number of children */
         return validate_numnodes(tree, nch + 1, "arglist");
 
+    if (nch > 1) {
+        for (i=0; i<nch; i++) {
+            if (TYPE(CHILD(tree, i)) == argument) {
+                node *ch = CHILD(tree, i);
+                if (NCH(ch) == 2 && TYPE(CHILD(ch, 1)) == gen_for) {
+                    err_string("need '(', ')' for generator expression");
+                    return 0;
+                }
+            }
+        }
+    }
+
     while (ok && nch-i >= 2) {
         /* skip leading (argument ',') */
         ok = (validate_argument(CHILD(tree, i))
@@ -2377,17 +2484,19 @@ validate_arglist(node *tree)
 
 /*  argument:
  *
- *  [test '='] test
+ *  [test '='] test [gen_for]
  */
 static int
 validate_argument(node *tree)
 {
     int nch = NCH(tree);
     int res = (validate_ntype(tree, argument)
-               && ((nch == 1) || (nch == 3))
+               && ((nch == 1) || (nch == 2) || (nch == 3))
                && validate_test(CHILD(tree, 0)));
 
-    if (res && (nch == 3))
+    if (res && (nch == 2))
+        res = validate_gen_for(CHILD(tree, 1));
+    else if (res && (nch == 3))
         res = (validate_equal(CHILD(tree, 1))
                && validate_test(CHILD(tree, 2)));