add env functions

3 files changed, 151 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index f53a3f0..c37b196 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-SOURCES = parse.c list.c atom.c eval.c tokens.c
+SOURCES = parse.c list.c atom.c eval.c tokens.c env.c
 OBJECTS = $(SOURCES:.c=.o)
 
 CFLAGS = -Wall -g
diff --git a/env.c b/env.c
new file mode 100644
index 0000000..e58ef70
--- /dev/null
+++ b/env.c
@@ -0,0 +1,134 @@
+#include "env.h"
+#include "list.h"
+#include "atom.h"
+
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+
+struct kv
+{
+    const char *symbol;
+    struct atom *value;
+};
+
+struct list *env_new()
+{
+    return list_new(NULL);
+}
+
+struct atom *env_lookup(struct list *env, const char *symbol)
+{
+    env = env->next;
+    while (env)
+    {
+        struct kv *kv = (struct kv *) env->data;
+
+        if (strcmp(kv->symbol, symbol) == 0)
+        {
+            return kv->value;
+        }
+
+        env = env->next;
+    }
+    return NULL;
+}
+
+int env_set_(struct list *env, const char *symbol,
+    struct atom *atom, int force)
+{
+    struct list *first = env;
+    struct kv *kv;
+
+    env = env->next;
+    while (env)
+    {
+        kv = (struct kv *) env->data;
+
+        if (strcmp(symbol, kv->symbol) == 0)
+        {
+            if (!force)
+                return 0;
+
+            kv->value = atom;
+
+            return 1;
+        }
+
+        if (!env->next)
+            break;
+
+        env = env->next;
+    }
+
+    if (!env)
+        env = first;
+
+    kv = calloc(1, sizeof(*kv));
+    kv->symbol = strdup(symbol);
+    kv->value = atom;
+
+    list_append(env, kv);
+
+    return 1;
+}
+
+struct list *env_extend(struct list *env, int count, ...)
+{
+    va_list ap;
+    int i;
+
+    struct list *result = env_clone(env);
+
+    va_start(ap, count);
+
+    for (i = 0; i < count; ++i)
+    {
+        const char *symbol = va_arg(ap, const char *);
+        struct atom *atom = va_arg(ap, struct atom *);
+        env_set_(result, symbol, atom, 1);
+    }
+
+    va_end(ap);
+
+    return result;
+}
+
+// struct list *env_extend_env(struct list *enva, struct list *envb)
+// {
+
+// }
+
+int env_set(struct list *env, const char *symbol,
+    struct atom *value)
+{
+    return env_set_(env, symbol, value, 0);
+}
+
+void env_free(struct list *env)
+{
+
+}
+
+struct list *env_clone(struct list *env)
+{
+    struct list *clone = env_new();
+    struct list *last = clone;
+
+    env = env->next;
+    while (env)
+    {
+        struct kv *kv = (struct kv *) env->data;
+
+        struct kv *kv_clone = malloc(sizeof(*kv_clone));
+
+        kv_clone->symbol = strdup(kv->symbol);
+        kv_clone->value = atom_clone(kv->value);
+
+        last = list_append(last, kv_clone);
+
+        env = env->next;
+    }
+
+    return clone;
+}
diff --git a/env.h b/env.h
new file mode 100644
index 0000000..6fcf8cc
--- /dev/null
+++ b/env.h
@@ -0,0 +1,16 @@
+#ifndef ENV_H
+#define ENV_H
+
+struct list;
+struct atom;
+
+struct list *env_new();
+struct atom *env_lookup(struct list *env, const char *symbol);
+struct list *env_extend(struct list *env, int count, ...); //const char *symbol, struct atom *value
+// struct list *env_extend_env(struct list *enva, struct list *envb);
+int env_set(struct list *env, const char *symbol,
+    struct atom *value);
+void env_free(struct list *env);
+struct list *env_clone(struct list *env);
+
+#endif