dup

diff --git a/implementations/uvm-ncc/joy.c b/implementations/uvm-ncc/joy.c
index f6cc29b..244d854 100644 (file)
--- a/implementations/uvm-ncc/joy.c
+++ b/implementations/uvm-ncc/joy.c
@@ -572,6 +572,7 @@ joy_eval(char *symbol, u32 stack, u32 expression)
        MATCH("clear") return (u64)expression;
        MATCH("swaack") { stack = swaack(stack); }
        else MATCH("pop") { stack = pop(stack); }
+       else MATCH("dup") { stack = dup(stack); }
        else MATCH("stack") { stack = cons(stack, stack); }
        //else MATCH("") { stack = (stack); }
        CHECK_ERROR
@@ -601,6 +602,17 @@ pop(u32 stack)
 
 
 u32
+dup(u32 stack)
+{
+       if (!stack) {
+               error = NOT_ENOUGH_VALUES_ON_STACK;
+               return 0;
+       }
+       return cons(head(stack), stack);
+}
+
+
+u32
 joy(u32 stack, u32 expression)
 {
        u32 term;
@@ -649,7 +661,7 @@ main()
        print_endl();
        */
 
-       u32 expression = text_to_expression("1 2 3 [4 5 6] swaack pop 23 stack 18");
+       u32 expression = text_to_expression("1 2 3 stack dup swaack");
        //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);