Add simple evaluation

src/main.c

@@ -1,10 +1,29 @@
+#include <assert.h>
 #include <stdio.h>
+
 #include "nihilispm.h"
 #include "nihilispm_state.h"
+#include "nihilispm_internal.h"
+#include "nihilispm_utility.h"
+#include "builtins.h"
 
 int main(int argc, const char **argv) {
     (void) argc, (void) argv;
     struct nl_state *state = nl_state_create();
 
+    nl_state_put(state, "+", nl_builtin_create(nl_builtin_add));
+    nl_state_put(state, "-", nl_builtin_create(nl_builtin_sub));
+    nl_state_put(state, "*", nl_builtin_create(nl_builtin_mul));
+    nl_state_put(state, "/", nl_builtin_create(nl_builtin_div));
+    nl_state_put(state, "%", nl_builtin_create(nl_builtin_mod));
+
+    struct nl_object *sexp = nl_parse(argv[1]);
+    struct nl_object *result = nl_evaluate(state, nl_car(sexp));
+
+    assert(result != NULL);
+    assert(result->type == NL_TYPE_INT);
+
+    printf("%d\n", result->integer);
+
     return 0;
 }