swap

diff --git a/implementations/uvm-ncc/joy.c b/implementations/uvm-ncc/joy.c
index a03d5ff..ca6a01b 100644 (file)
--- a/implementations/uvm-ncc/joy.c
+++ b/implementations/uvm-ncc/joy.c
@@ -560,6 +560,7 @@ text_to_expression(char *str)
        return top;
 }
 
+
 /*
 In order to return two "pointers" I'm going to just OR them
 into one u64 value.  It might be conceptually cleaner to define
@@ -583,7 +584,8 @@ joy_eval(char *symbol, u32 stack, u32 expression)
        else MATCH("pop") { stack = pop(stack); }
        else MATCH("dup") { stack = dup(stack); }
        else MATCH("stack") { stack = cons(stack, stack); }
-       // first, rest, swap, ...
+       else MATCH("swap") { stack = swap(stack); }
+       // first, rest, ...
        //else MATCH("") { stack = (stack); }
        CHECK_ERROR
        //print_str(symbol);print_endl();
@@ -619,6 +621,23 @@ dup(u32 stack)
 
 
 u32
+swap(u32 stack)
+{
+       u32 tos = pop_any(stack);
+       CHECK_ERROR
+       stack = tail(stack);
+       u32 second = pop_any(stack);
+       CHECK_ERROR
+       stack = tail(stack);
+       stack = cons(tos, stack);
+       CHECK_ERROR
+       stack = cons(second, stack);
+       CHECK_ERROR
+       return stack;
+}
+
+
+u32
 joy(u32 stack, u32 expression)
 {
        u32 term;
@@ -670,7 +689,7 @@ main()
        print_endl();
        */
 
-       u32 expression = text_to_expression("1 2 3 stack dup swaack");
+       u32 expression = text_to_expression("1 2 3 stack dup swaack swap");
        //u32 expression = text_to_expression("1 2 3 clear 4 5 6");
        //u32 expression = text_to_expression(" 1[2[true 3][aa[aa bb] aa bb cc]bob]false[]bob 3[4] ga[]ry");
        print_joy_list(expression);