4 ms·

I have a feeling you don't have much CL experience... There really aren't very many CL destructive (mutating) list functions, and I personally almost never use

I have a feeling you don't have much CL experience... There really aren't very many CL destructive (mutating) list functions, and I personally almost never use them except on fresh lists (like for example when I nreverse a list I just created with successive pushes) and I'm pretty sure it's standard practice. Let's see what destructive list functions I can find in CL (ref: http://www.lispworks.com/documentation/HyperSpec/Body/c_conses.htm http://www.lispworks.com/documentation/HyperSpec/Body/c_cons...) rplaca, rplacd, nsublis, nsubst*, nconc, nreconc, nbutlast, mapcan, mapcon, nintersection, nset-difference, nset-exclusive-or I took some liberties but that's about 12/58 = 20% destructive functions (push, pop, pushnew are usually used on variables, not list structure). And good style dictates to use them very sparsely... Also, (loop for x in some-list sum (* 2 x)) is pretty functional, you're just mutating x locally but who cares, this is exactly like saying (apply #'+ (mapcar (lambda (x) (* 2 x)))) which is obviously functional.

Hexstream 18y ago
I knew something wasn't quite right. I forgot the sequence functions. So add this to the list: fill, map-into, nreverse, replace, nsubstitute, merge, delete, delete-duplicates So about 20/85 = 23,5%
jrockway 18y ago
Point conceded. The post I replied to says "CL discourages mutation" which is not true. I said "nearly all sequence functions are destructive", which is also not true. Upon further reflection, I think we can say CL doesn't really care if you mutate or not. There's more than one way to do it :)
- Hexstream 18y ago
  CL does discourage mutation... With all the structure sharing going on in CL programs you can't afford mutating things thoughtlessly.
  - jrockway 18y ago
    But OTOH, if you are careful about mutating when possible, your program will run faster. Not the most important thing in the world, I agree, but it is a "reward" for mutating things.
- plinkplonk 18y ago
  Upvoted for "Point conceded.". We don't see enough of this.
- anamax 18y ago
  > I said "nearly all sequence functions are destructive", Actually, you said "nearly all of the standard list functions". You do know that CL has sequences that are not lists, right?

Hexstream 18y ago

I knew something wasn't quite right. I forgot the sequence functions. So add this to the list: fill, map-into, nreverse, replace, nsubstitute, merge, delete, delete-duplicates So about 20/85 = 23,5%

jrockway 18y ago

Point conceded. The post I replied to says "CL discourages mutation" which is not true. I said "nearly all sequence functions are destructive", which is also not true. Upon further reflection, I think we can say CL doesn't really care if you mutate or not. There's more than one way to do it :)

Hexstream 18y ago
CL does discourage mutation... With all the structure sharing going on in CL programs you can't afford mutating things thoughtlessly.
- jrockway 18y ago
  But OTOH, if you are careful about mutating when possible, your program will run faster. Not the most important thing in the world, I agree, but it is a "reward" for mutating things.
plinkplonk 18y ago
Upvoted for "Point conceded.". We don't see enough of this.
anamax 18y ago
> I said "nearly all sequence functions are destructive", Actually, you said "nearly all of the standard list functions". You do know that CL has sequences that are not lists, right?