a better way - apply/mapcar/lambda/mapcar/lambda

[Daron Denton]

school me please.
I want to prefix '("BBB" "CCC" "DDD") with '("aaa" "AAA"), and combine as one string, comma delimited.

(apply 'strcat
(apply 'append
(mapcar '(lambda (A )
(mapcar '(lambda (X )
(strcat A X ",")
)
'("BBB" "CCC" "DDD")
)
)
'("aaa" "AAA")
)))

correctly returns "aaaBBB,aaaCCC,aaaDDD,AAABBB,AAACCC,AAADDD,"

Is there a more elegant way of doing this?

 

[Devin]

(defun C:TEST
(setq str "")
(foreach a '("aaa" "bbb")
(foreach b '("BBB" "CCC" "DDD")
(setq str (strcat str a b ","))
)
)
)

 

[Ken Alexander]

Don't know if it's any better.......

(setq newlist ')
(foreach x '("aaa" "AAA")
(setq newlist
(append newlist
(mapcar
'(lambda (y)
(strcat x y ","))
'("BBB" "CCC" "DDD"))))
)

 

[Devin]

Why are you trying to process without the foreach?

Devin

 

[Daron Denton]

mapcar processes lists faster than foreach

 

[Devin]

I didn't know that, thanks!

Devin

 

[Devin]

Daron,

You might want to do a timing check, just to see which is faster in this case. The other way seems to add steps in the process, which my increase the runtime required.

Devin

 

[Daron Denton]

There has been much of that here in the past. That's why i posted, hoping one of the list pro's would chime in. Mine is overkill for the example, but it's been simplified here for testing. When the '("BBB" "CCC" "DDD") list contains over 100 items, it makes a difference.

 

[Devin]

I see.

Devin

 

[Ken Alexander]

Very minor change to your original:

(apply 'strcat
(mapcar '(lambda (y)
(apply 'strcat
(mapcar '(lambda (x)
(strcat y x ","))
'("BBB" "CCC" "DDD"))
))
'("aaa" "AAA")
)
)

 

[Jason Piercey]

I believe that depends on the list.

 

[Devin]

As I seem to be learning. I found that when I switched to mapcar my list processing was much faster. I wonder why it's foreach is slower?

Devin