Implement while

src/CMakeLists.txt

@@ -64,6 +64,7 @@ functionaltest("len")
 functionaltest("not")
 functionaltest("type")
 functionaltest("if")
+functionaltest("while")
 
 install(TARGETS apfl DESTINATION lib)
 install(TARGETS apfl-bin DESTINATION bin)

src/apfl.h

@@ -657,6 +657,8 @@ enum apfl_value_type apfl_get_type(apfl_ctx, apfl_stackidx);
 void apfl_drop(apfl_ctx, apfl_stackidx);
 // Move a value to the top of the stack
 void apfl_move_to_top_of_stack(apfl_ctx, apfl_stackidx);
+// Copy a value to the top of the stack
+void apfl_copy(apfl_ctx ctx, apfl_stackidx index);
 // Push a nil onto the stack
 void apfl_push_nil(apfl_ctx);
 // Push a boolean onto the stack

src/context.c

@@ -427,6 +427,13 @@ apfl_move_to_top_of_stack(apfl_ctx ctx, apfl_stackidx index)
     }
 }
 
+void
+apfl_copy(apfl_ctx ctx, apfl_stackidx index)
+{
+    struct apfl_value value = apfl_stack_must_get(ctx, index);
+    apfl_stack_must_push(ctx, apfl_value_set_cow_flag(value));
+}
+
 void
 apfl_stack_clear(apfl_ctx ctx)
 {

src/functional-tests/while.at

@@ -0,0 +1,28 @@
+===== script =====
+i = 0
+while { (not (== i 10)) } {
+    print i
+    i = + i 1
+}
+
+i = 0
+print (while { (not (== i 10)) } {
+    i = + i 1
+    * 10 i
+})
+
+print (while {false} {"fail"})
+
+===== output =====
+0
+1
+2
+3
+4
+5
+6
+7
+8
+9
+100
+nil

src/globals.c

@@ -274,6 +274,42 @@ type(apfl_ctx ctx)
     apfl_push_const_string(ctx, typestr(apfl_get_type(ctx, -1)));
 }
 
+static void
+impl_while(apfl_ctx ctx)
+{
+    size_t argc = apfl_len(ctx, 0);
+    if (argc != 2) {
+        apfl_raise_const_error(ctx, APFL_RESULT_ERR, "while needs 2 functions as arguments");
+    }
+
+    apfl_get_list_member_by_index(ctx, 0, 0);
+    if (apfl_get_type(ctx, -1) != APFL_VALUE_FUNC) {
+        apfl_raise_const_error(ctx, APFL_RESULT_ERR, "while needs 2 functions as arguments");
+    }
+    apfl_get_list_member_by_index(ctx, 0, 1);
+    if (apfl_get_type(ctx, -1) != APFL_VALUE_FUNC) {
+        apfl_raise_const_error(ctx, APFL_RESULT_ERR, "while needs 2 functions as arguments");
+    }
+
+    apfl_drop(ctx, 0);
+
+    apfl_push_nil(ctx); // Return value in case of no iteration
+
+    for (;;) {
+        apfl_copy(ctx, 0);
+        apfl_list_create(ctx, 0);
+        apfl_call(ctx, -2, -1);
+        if (!apfl_is_truthy(ctx, -1)) {
+            break;
+        }
+
+        apfl_drop(ctx, -1);
+        apfl_copy(ctx, 1);
+        apfl_list_create(ctx, 0);
+        apfl_call(ctx, -2, -1);
+    }
+}
+
 static const struct global_def globals[] = {
     {"if", impl_if},
     {"==", impl_eq},
@@ -288,6 +324,7 @@ static const struct global_def globals[] = {
     {"not", not},
     {"len", len},
     {"type", type},
+    {"while", impl_while},
     {NULL, NULL},
 };