Implement loops + create variable when assigning to non-existent var

src/bc_compiler.c

@@ -374,7 +374,23 @@ void ast_to_bc ( BCCompilerState * state, Ast * ast ) {
       if ( index == 65535 ) {
         // GLOBAL
         u16 str_index = get_string_index ( state, assign -> name );
-        assert ( str_index != 0 );
+        if ( str_index == 0 ) {
+          // create global / local
+          if ( state -> scope == state -> top ) {
+            str_index = make_string_index ( state, assign -> name );
+            u16 * count = & state -> globals . global_count;
+            state -> globals . names [ *count ] = str_index;
+            ++(*count);
+            string_write_byte ( & function -> bc, 0x0B );
+            string_write_u16 ( & function -> bc, str_index );
+            return;
+          } else {
+            index = make_local_index ( state, assign -> name );
+            string_write_byte ( & function -> bc, 0x09 );
+            string_write_u16 ( & function -> bc, index );
+            return;
+          }
+        }
         u16 * count = & state -> globals . global_count;
         size_t i;
         for ( i = 0; i < *count; ++i )
@@ -417,6 +433,31 @@ void ast_to_bc ( BCCompilerState * state, Ast * ast ) {
       function -> bc . str [ cons_pos - 1 ] = (cons_len >> 8) & 255;
       return;
     }
+    case AST_LOOP: {
+      AstLoop * loop = (AstLoop*) ast;
+      BCFunction * function = & state -> constants . constants [ state -> fp ] . function;
+      ast_to_bc ( state, (Ast*) & (AstNull) { .base = (Ast) { .kind = AST_NULL } } ); 
+      size_t start_pos = function -> bc . len;
+      ast_to_bc ( state, loop -> condition );
+      string_write_byte ( & function -> bc, 0x0D );
+      string_write_u16  ( & function -> bc, 3 );
+      string_write_byte ( & function -> bc, 0x0E );
+      string_write_u16  ( & function -> bc, 0 );
+      size_t body_pos = function -> bc . len;
+      add_scope ( state );
+      ast_to_bc ( state, loop -> body );
+      remove_scope ( state );
+      string_write_byte ( & function -> bc, 0x0E );
+      string_write_u16  ( & function -> bc, 0 );
+      size_t after_pos = function -> bc . len;
+      i16 loop_len = after_pos - start_pos;
+      function -> bc . str [ after_pos - 2 ] = (-loop_len) & 255;
+      function -> bc . str [ after_pos - 1 ] = ((-loop_len) >> 8) & 255;
+      u16 body_len = after_pos - body_pos;
+      function -> bc . str [ body_pos - 2 ] = body_len & 255;
+      function -> bc . str [ body_pos - 1 ] = (body_len >> 8) & 255;
+      return;
+    }
     default:
       assert ( false );
   }