add file related functions

src/file.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+
+#include "picrin.h"
+
+pic_value
+pic_file_exists_p(pic_state *pic)
+{
+  char *fname;
+  size_t size;
+  FILE *fp;
+
+  pic_get_args(pic, "s", &fname, &size);
+
+  fp = fopen(fname, "r");
+  if (fp) {
+    fclose(fp);
+    return pic_true_value();
+  } else {
+    return pic_false_value();
+  }
+}
+
+pic_value
+pic_file_delete(pic_state *pic)
+{
+  char *fname;
+  size_t size;
+
+  pic_get_args(pic, "s", &fname, &size);
+
+  if (remove(fname) != 0) {
+    pic_error(pic, "file cannot be deleted");
+  }
+  return pic_true_value();
+}
+
+void
+pic_init_file(pic_state *pic)
+{
+  pic_defun(pic, "file-exists?", pic_file_exists_p);
+  pic_defun(pic, "delete-file", pic_file_delete);
+}

src/init.c

@@ -4,6 +4,7 @@ void pic_init_port(pic_state *);
 void pic_init_number(pic_state *);
 void pic_init_time(pic_state *);
 void pic_init_system(pic_state *);
+void pic_init_file(pic_state *);
 
 #define DONE pic_gc_arena_restore(pic, ai);
 
@@ -17,4 +18,5 @@ pic_init_core(pic_state *pic)
   pic_init_number(pic); DONE;
   pic_init_time(pic); DONE;
   pic_init_system(pic); DONE;
+  pic_init_file(pic); DONE;
 }