Add error types and simple state

src/state.c

@@ -0,0 +1,60 @@
+#include "nihilispm.h"
+#include "nihilispm_internal.h"
+#include "nihilispm_state.h"
+#include "nihilispm_utility.h"
+
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+
+// Implements state as a giant alist
+// TODO: Consider generalizing the alist concept
+
+struct nl_state {
+    struct nl_object *list;
+};
+
+#define NAME_POSITION 0
+#define DATA_POSITION 1
+
+
+static struct nl_object *nl_state_get_cell(struct nl_state *state, const char *name) {
+    FOREACH_LIST(state->list, iter, item) {
+        assert(item->type == NL_TYPE_CELL);
+        const char *item_name = nl_list_nth(item, NAME_POSITION)->string;
+        if (!strcmp(name, item_name)) {
+            return item;
+        }
+    }
+
+    return NULL;
+}
+
+struct nl_object *nl_state_get(struct nl_state *state, const char *name) {
+    struct nl_object *cell = nl_state_get_cell(state, name);
+    NL_COND_OR_RET_ERROR(cell != NULL, "Unknown name");
+    return nl_list_nth(cell, DATA_POSITION);
+}
+
+void nl_state_put(struct nl_state *state, const char *name, struct nl_object *obj) {
+    struct nl_object *cell = nl_state_get_cell(state, name);
+    if (cell == NULL) {
+        nl_list_append(state->list,
+                       nl_tuple_create(
+                           nl_string_create(strdup(name)),
+                           obj));
+    } else {
+        // TODO: Refcounting / cleanup
+        cell->cell.cdr->cell.car = obj;
+    }
+}
+
+struct nl_state *nl_state_create() {
+    struct nl_state *state = malloc(sizeof(struct nl_state));
+    state->list = nl_nil_create();
+    return state;
+}
+
+void nl_state_delete(struct nl_state *state) {
+    nl_object_delete(state->list);
+}