iris

commit 2a05ed0a3743603003afeb9f36fa5912bdb9c10d
parent 4db212d423da3639af21f77dce6bf2d897d8fcc3
Author: sin <sin@2f30.org>
Date:   Thu, 15 May 2014 17:03:03 +0100

Add diff

Diffstat:
M
parser.c
 | 
27
+++++++++++++++++++++++++++

1 file changed, 27 insertions(+), 0 deletions(-)
diff --git a/parser.c b/parser.c
@@ -60,6 +60,7 @@ struct object {
 };
 
 static struct object *evaldefine(struct object *);
+static struct object *evaldiff(struct object *);
 static struct object *evalif(struct object *);
 static struct object *evalok(struct object *);
 static struct object *evalplus(struct object *);
@@ -72,6 +73,7 @@ struct {
 	struct object *(*fn)(struct object *);
 } builtins[] = {
 	{ .name = "define", .fn = evaldefine },
+	{ .name = "diff",   .fn = evaldiff   },
 	{ .name = "if",     .fn = evalif     },
 	{ .name = "ok",     .fn = evalok     },
 	{ .name = "plus",   .fn = evalplus   },
@@ -324,6 +326,31 @@ evaldefine(struct object *o)
 }
 
 static struct object *
+dodiff(struct object *o, struct object *n)
+{
+	if (!car(o))
+		return n;
+	if (car(o)->type != ONumber)
+		return error("expected number");
+	n->d.n.v -= car(o)->d.n.v;
+	return dodiff(cdr(o), n);
+}
+
+static struct object *
+evaldiff(struct object *o)
+{
+	struct object *ocar;
+
+	if (o->type != OPair)
+		return NULL;
+	ocar = car(o);
+	if (ocar->type != OIdentifier ||
+	    strcmp(ocar->d.i.s, "diff") != 0)
+		return NULL;
+	return dodiff(cdr(o), number(0));
+}
+
+static struct object *
 evalif(struct object *o)
 {
 	struct object *ocar;