on the OLPC wiki, there's NIP ( a b -- b ) and TUCK ( a b -- b a b ) and -ROT ( a b c -- c a b ) which I call LROT, but what is the word which has the stack diagram ( a b c -- b a c ) ? Is it UNDER?

I would be tempted to name them bca, bac, cab, and cba, but I have a perverse affinity for three-letter mnemonics.

(CAAR x) == (CAR (CAR x))
(CADR x) == (CAR (CDR x))
(CDDR x) == (CDR (CDR x))
(CDAR x) == (CDR (CAR x))

I was thinking the same thing.

Lisp actually does exactly this with CAR and CDR combinations.

Such that you have several things like:


I think many have all the combinations out to 5 letters (CAAAR).

FLIP ( a b c -- b a c )
FLOP ( a b c -- c b a )

I'm going to call them FLIP and FLOP for now, until I find out what the names are supposed to be.

I think that what chitselb means is that every stack manipulation should have a name, not that every conceivable stack manipulation (no matter how rarely used) should be implemented in a Forth system. It is a simple matter to write a CODE word for any manipulation that isn't in your Forth system but is likely to be used a lot in a program. I have often found 2PICK to be such a word.

for "flop" I would probably use ROTSWAP if I needed the word or SWAPUNDER if the former name was not descriptive enough.
"flip" would probably sound better as 3REVERSE. (I hope I didn't get "flip" and "flop" mixed up. )

I have often found 2PICK to be such a word.