rc

commit 7a643120366f1ea24eac5ccb759d4df616e7789b
parent 2dd0aa249c9bac4e5c616d1f386dc4271fdbab46
Author: Toby Goodwin <toby@paccrat.org>
Date:   Mon, 19 Mar 2018 20:55:56 +0000

implement desugaring version (again, lost due to git problem)

Diffstat:
M
ChangeLog
 | 
8
++++++++
M
rc.h
 | 
2
+-
M
tree.c
 | 
47
++++++++++++++++++++++++++++++++++++++++-------
M
trip.rc
 | 
3
++-

4 files changed, 51 insertions(+), 9 deletions(-)
diff --git a/ChangeLog b/ChangeLog
@@ -911,3 +911,11 @@ Changes since rc-1.5b2
   Bug: the grammar disallowed local assignments and redirections in the true
   branch of `if` when there was an `else` clause (thanks Dražen Borković and
   Bert Münnich; github #31).
+
+2018-03-17
+
+  Feature: implement the `flag` builtin.
+
+2018-03-19
+
+  Feature: implement `if not`.
diff --git a/rc.h b/rc.h
@@ -371,7 +371,7 @@ extern volatile sig_atomic_t slow;
 
 
 /* tree.c */
-extern Node *mk(int /*nodetype*/,...);
+extern Node *mk(enum nodetype, ...);
 extern Node *treecpy(Node *, void *(*)(size_t));
 extern void treefree(Node *);
 
diff --git a/tree.c b/tree.c
@@ -2,9 +2,47 @@
 
 #include "rc.h"
 
+/* convert if followed by ifnot to else */
+static Node *desugar_ifnot(Node *n) {
+	if (n->type == nBody && n->u[1].p && n->u[1].p->type == nIfnot) {
+		/* (body (if c x) (if-not y)) => (body (if c (else x y))) */
+		if (n->u[0].p->type == nIf) {
+			Node *yes = n->u[0].p;
+			Node *no = n->u[1].p;
+			Node *els = nalloc(offsetof(Node, u[2]));
+			els->type = nElse;
+			els->u[1].p = no->u[0].p;
+			els->u[0].p = yes->u[1].p;
+			yes->u[1].p = els;
+			n->u[1].p = NULL;
+		} else goto fail;
+	} else if (n->type == nBody &&
+			n->u[1].p && n->u[1].p->type == nBody &&
+			n->u[1].p->u[0].p &&
+				n->u[1].p->u[0].p->type == nIfnot) {
+		/* (body (if c x) (body (if-not y) z)) =>
+			(body (if c (else x y)) z) */
+		if (n->u[0].p->type == nIf) {
+			Node *yes = n->u[0].p;
+			Node *no = n->u[1].p->u[0].p;
+			Node *els = nalloc(offsetof(Node, u[2]));
+			els->type = nElse;
+                        els->u[1].p = no->u[0].p;
+                        els->u[0].p = yes->u[1].p;
+                        yes->u[1].p = els;
+                        n->u[1].p = n->u[1].p->u[1].p;
+		} else goto fail;
+	}
+
+	return n;
+fail:
+	rc_error("`if not' must follow `if'");
+	return NULL;
+}
+
 /* make a new node, pass it back to yyparse. Used to generate the parsetree. */
 
-extern Node *mk(int /*nodetype*/ t,...) {
+extern Node *mk(enum nodetype t,...) {
 	va_list ap;
 	Node *n;
 	va_start(ap, t);
@@ -60,13 +98,8 @@ extern Node *mk(int /*nodetype*/ t,...) {
 		break;
  	}
 	n->type = t;
-        if (t == nBody && n->u[1].p && n->u[1].p->type == nIfnot) {
-                if (n->u[0].p->type == nIf) {
-                        fprint(2, "here i am!\n");
-                } else
-                        rc_error("`if not' must follow `if'");
 
-        }
+	n = desugar_ifnot(n);
 	va_end(ap);
 	return n;
 }
diff --git a/trip.rc b/trip.rc
@@ -706,7 +706,8 @@ if (~ $status 0) {
 
 # exercise "if not"
 submatch 'if (false) echo foo; if not echo bar' 'bar' 'if not 1'
-submatch 'if (false) echo foo; echo qux; if not echo bar' 'rc: `if not'' must follow `if''' 'if not 2'
+submatch 'if (false) echo -n foo; if not echo -n bar; echo qux' 'barqux' 'if not 2'
+submatch 'if (false) echo foo; echo qux; if not echo bar' 'rc: `if not'' must follow `if''' 'if not 3'
 
 # exercise flag builtin
 submatch 'flag' 'rc: not enough arguments to flag' 'flag no args'