tisp

commit 9c817c76b1a5965203db65704be6770102d6cb0f
parent 5ec23fca3e25c5a0dee3baaa82802831dc502fec
Author: Ed van Bruggen <edvb@uw.edu>
Date:   Sat, 26 Dec 2020 21:53:06 -0800

Add defined? function

Returns bool on if symbol given is assigned a value

Diffstat:
test.c
 | 
6
++++++
tisp.c
 | 
15
+++++++++++++++

2 files changed, 21 insertions(+), 0 deletions(-)
diff --git a/test.c b/test.c
@@ -205,6 +205,12 @@ char *tests[][2] = {
 	{ "add2",                        "2"       },
 	{ "(set! add2 \"2\")",           "2"       },
 	{ "add2",                        "2"       },
+	{ "defined?",                    NULL      },
+	{ "(defined? invalid-var)",      "Nil"     },
+	{ "(defined? defined?)",         "True"    },
+	{ "(defined? car)",              "True"    },
+	{ "(defined? when)",             "True"    },
+	{ "(defined? apply)",            "True"    },
 
 	{ "lambda",                       NULL },
 	{ "((lambda (x) x) 3)",           "3"  },
diff --git a/tisp.c b/tisp.c
@@ -1000,6 +1000,20 @@ form_set(Tsp st, Hash env, Val args)
 	return val;
 }
 
+static Val
+form_definedp(Tsp st, Hash env, Val args)
+{
+	Entry e = NULL;
+	tsp_arg_min(args, "defined?", 1);
+	tsp_arg_type(car(args), "defined?", TSP_SYM);
+	for (Hash h = env; h; h = h->next) {
+		e = entry_get(h, car(args)->v.s);
+		if (e->key)
+			break;
+	}
+	return (!e || !e->key) ? st->nil : st->t;
+}
+
 /* loads tisp file or C dynamic library */
 /* TODO lua like error listing places load looked */
 /* TODO only use dlopen if -ldl is given with TIB_DYNAMIC */
@@ -1117,6 +1131,7 @@ tisp_env_init(size_t cap)
 	tsp_env_form(def);
 	tsp_env_name_form(set!, set);
 	tsp_env_prim(load);
+	tsp_env_name_form(defined?, definedp);
 	tsp_env_prim(error);
 	tsp_env_form(version);