> Is that it's only use? Then why? dip can easily be formulated using > non-retain stack using primitives: > > For example: "a" "b" "c" [ append ] dip -> "a" "b" "c" -rot append swap >
That implementation assumes the quotation takes two operands and produces one result, which is not always the case. More generally, the functional argument of “dip” is not really supposed to be able to touch the argument it’s operating under. If you don’t have types or a stack checker enforcing this, the formulations with a retain stack or dynamically composing quotations are safe by construction, but the “-rot” version is not. Consider “[ 3drop ] dip” or “[ append dup ] dip”. You can easily describe the constraint with a type dependent on the arity of the argument type, though. In the current state of Kitten: dip :: ∀R S a. (R a (R → S) → S a) ------------------------------------------------------------------------------ "Accelerate Dev Cycles with Automated Cross-Browser Testing - For FREE Instantly run your Selenium tests across 300+ browser/OS combos. Get unparalleled scalability from the best Selenium testing platform available Simple to use. Nothing to install. Get started now for free." http://p.sf.net/sfu/SauceLabs _______________________________________________ Factor-talk mailing list Factor-talk@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/factor-talk
