Build a REPL for ucLISP

Still some rough edges

src/main.c

@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "uclisp.h"
+#include "types.h"
+
+#ifdef PLATFORM_PICO_SDK
+#include "pico/stdio.h"
+#include "pico/stdlib.h"
+#endif
+
+struct ucl *ucl;
+
+// TODO: Get these from a header
+struct ucl_object *ucl_car(struct ucl*, struct ucl_object *);
+void ucl_print_obj(struct ucl_object *);
+
+int main() {
+
+#ifdef PLATFORM_PICO_SDK
+    stdio_usb_init();
+    gpio_init(PICO_DEFAULT_LED_PIN);
+    gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT);
+    bool gpio_state = false;
+#endif
+
+    ucl = ucl_create();
+
+    while(1) {
+#ifdef PLATFORM_PICO_SDK
+        gpio_put(PICO_DEFAULT_LED_PIN, gpio_state);
+        gpio_state = !gpio_state;
+#endif
+
+        // TODO: Work out input for pico
+        size_t line_len = 512;
+        char *line = NULL;
+        printf("> ");
+        getline(&line, &line_len, stdin);
+
+        struct ucl_object *sexp = ucl_parse(ucl, line);
+        struct ucl_object *result = NULL;
+        if (sexp->type == UCL_TYPE_ERROR) {
+            result = sexp;
+        } else {
+            result = ucl_evaluate(ucl, ucl_car(ucl, sexp));
+        }
+        ucl_print_obj(result);
+        printf("\n");
+        ucl_gc(ucl);
+        free(line);
+    }
+
+    return 0;
+}