newLISP Challenge: The seemingly simple 'my-or'

[DrDave]

Does this work for you?

Code Select Expand

(define-macro (my-or)
   (let (
         temp  (eval (args 0))
         temp1 (eval (args 1))
        )
     (if temp
         temp
         temp1
     )

    )
)



results:

Code Select Expand

(my-or temp nil) = 45
(my-or nil temp) = 45
-----------
first arg
should be 1: 1
-----------
first arg
second arg
should be 2: 2

[m i c h a e l]

Here's a minimal version:

Code Select Expand

(define-macro (my-or)
   (or (eval (args 0)) (eval (args 1)))
)


m i c h a e l

[itistoday]

Does this work for you?



results:

How did you get those results? With that code the second argument is always evaluated, therefore producing this result:

Code Select Expand

(my-or temp nil) = 45
(my-or nil temp) = 45
-----------
first arg
second arg
should be 1: 1
-----------
first arg
second arg
should be 2: 2

[itistoday]

Here's a minimal version:

Code Select Expand

(define-macro (my-or)
   (or (eval (args 0)) (eval (args 1)))
)


That's cheating. :-p



I guess I didn't state it, but part of the idea/challenge is that you're supposed to define your own 'or', if you could use the built-in 'or' then it wouldn't really be a challenge..

[DrDave]

How did you get those results? With that code the second argument is always evaluated, therefore producing this result:

Code Select Expand

(my-or temp nil) = 45
(my-or nil temp) = 45
-----------
first arg
second arg
should be 1: 1
-----------
first arg
second arg
should be 2: 2

Ah, my bad. You're right. I didn't look carefully at the results.

[xytroxon]

Here's a minimal version:

Code Select Expand

(define-macro (my-or)
   (or (eval (args 0)) (eval (args 1)))
)


That's cheating. :-p



I guess I didn't state it, but part of the idea/challenge is that you're supposed to define your own 'or', if you could use the built-in 'or' then it wouldn't really be a challenge..

Inheritance is a powerful (and in 2009), a fundamental programming concept... For OOP, or for LISP, which at it's core "invented" inheritance by it's "functional" programming language nature... Every new function "inherits" code from existing functions... "or" is the base function... "my-or" is the derived functionality that reuses the "or" code and extends it's functionality... Using the "if" function is no more, or no less a valid idiom than using the "or" function...



Michael's version is clear, concise, and I can understand at a glance what it is doing... It is "pure"... It is "beautiful"... The only potential fault with such "beauty" is that it must also work... In real world programming, functionality must always trump beautiful form... When both functional form and beauty come together, it is rare, and profound...



"OR" is this to be an obfuscated newLISP contest? ;-)



-- xytroxon

[itistoday]

Not an obfuscated contest, no, just a challenge to see if you can figure out a way to do it. While working on this problem myself I came up with what I thought was a clever little solution and I thought it would make for a fun topic/challenge. :-)

[newdep]

(define-macro (my-or)

   (not (and (eval (args 0)) (eval (args 1))))

)



but probably thats a sidekick ;-)

[itistoday]

but probably thats a sidekick ;-)

Yeah... but in addition that doesn't produce the correct results:

Code Select Expand

(my-or temp nil) = true
(my-or nil temp) = true
-----------
first arg
second arg
should be 1: nil
-----------
first arg
should be 2: true

[newdep]

yeah Im still looking into it because I want small code result ;-)

So i like micheal solution but im aming for a more scheme lookalike..

[newdep]

I cant get closer then this to scheme..

Code Select Expand


(define-macro (my-or)
 (let (temp
  (unless (eval (args 0))  
   (eval (args 1))))  
    temp))  

Code Select Expand

(my-or temp nil) = 45
(my-or nil temp) = 45
-----------
first arg
should be 1: 1
-----------
first arg
second arg
should be 2: 2



At least its short (shorter then the if version)

returns the values correctly and doesnt drop variables..



But then again it uses (args) and it uses 'unless (which is an 'or).





PS: Dropin another quizzzzzzzzzz ;-)

[xytroxon]

(define-macro (my-or)

   (not (and (eval (args 0)) (eval (args 1))))

)



but probably thats a sidekick ;-)

LOL!!!



I love these code challenges :-)



But the quest should always be for the shortest path...



In other LISPs "eval" can be a speed hog (major slow down)...



-- xytroxon

[itistoday]

I cant get closer then this to scheme..

Code Select Expand


(define-macro (my-or)
 (let (temp
  (unless (eval (args 0))  
   (eval (args 1))))  
    temp))  

Code Select Expand

(my-or temp nil) = 45
(my-or nil temp) = 45
-----------
first arg
should be 1: 1
-----------
first arg
second arg
should be 2: 2



At least its short (shorter then the if version)

returns the values correctly and doesnt drop variables..



But then again it uses (args) and it uses 'unless (which is an 'or).





PS: Dropin another quizzzzzzzzzz ;-)

Congrats newdep! That's a valid solution!



It is similar in principle to the one I came up with, but actually yours is better because it is much faster. In fact it's almost as fast as placing the macro in its own namespace.  Send me a PM with your full name and email if you'd like a license to Espionage.



Here is the one I came up with, as you can see the principle of avoiding the evaluation is sortof the same, whereas you do it with 'unless', I did it with the exception mechanism. ](define-macro (my-or)
   (catch
      (begin
         (let (temp (eval (args 0)))
            (if temp (throw temp))
         )
         (throw (eval (args 1)))
      )
   )
)[/code]

[itistoday]

Yes, the 'unless' and 'or' are similar, but the 'or' solution as was presented was equivalent to doing this (and therefore not an acceptable solution):

Code Select Expand

(set 'my-or or)

I was mainly looking for something similar to what I had, which I feel your solution was, as it used the same principle of avoiding the extra evaluation that was in DrDave's code while avoiding variable capture as well.



I hope though that nobody actually writes their macros this way, as to an outsider it would be completely non-obvious why the extra hoop-jumping was taking place.



This just demonstrates the need for a http://www.alh.net/newlisp/phpbb/viewtopic.php?t=2714">define-smacro in newLISP.

[newdep]

Aha...I win finaly something here ;-)

Thanks for the price.. I dont have a Mac with OSX only

a MacClassic and an IMac.. But If you dont mind I would Like to store

you kind generosity for the "yearly newlisp Contest".. Where a winner

then also could get your nice software package.. (If thats oke with you, it would be a nice addon for the price shelf...)



Coming back to the Scheme example, I think its somehow unfair too what

Scheme does with GenSym. So personaly I prefer the newlisp (arg) way

of solving this. Where GenSym is a nice workaround its also not transparent for the function..



..I liked the quizzzz.. nice brain trainers these are...