3 ms·

It's been a long time since I used common lisp, but I seem to remember that the convention was to use if in a conditional expression and when for something that

It's been a long time since I used common lisp, but I seem to remember that the convention was to use if in a conditional expression and when for something that conditionally produces a side effect?

diggan 7y ago
If it's anything like Clojure (big assumption, but skimming the submission link seems to confirm things are the same), `if` is used when you want to do something OR do something else. You use `when` only when there is no `OR do something else` and/or when there is multiple things you want to do inside.
- pvinis 7y ago
  It's interesting to see how you use your if and when in your sentences. Surprisingly, you have an if without an else, and a when with an or at the end! :p I do remember that convention though, and it makes sense. I just found your usages in text interesting.
  - diggan 7y ago
    Haha, you're right! Re-reading my own comment, I seem to switch context between "normal language" conditionals where the rules obviously are different from the "programming language" context where they are strictly defined. Fun observation :)
aidenn0 7y ago
When has no else and if has no explicit progn. If you need an else for a side effect then cond or if will be used. I don't think there is a consensus on which of those to use for side effect vs expression when an else is needed
- arethuza 7y ago
  I probably got that idea from CLtL: https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node84.html https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node84.html Very much a "stylistic preference" though! Edit: I realised that for the 6 years or so I wrote CL as part of my day job that my well thumbed copy of CLtL was by far the most referenced programming language book I have ever used (mostly falling open at either the loop or CLOS chapters). Not sure what this says about CL!
reikonomusha 7y ago
This is a style rule at Rigetti Computing: use IF or COND when the return value matters and no side effects; use WHEN, UNLESS, COND if you have side effects. (Never use IF for side effects, never use WHEN/UNLESS for return values.)

It's been a long time since I used common lisp, but I seem to remember that the convention was to use if in a conditional expression and when for something that conditionally produces a side effect?

diggan 7y ago

If it's anything like Clojure (big assumption, but skimming the submission link seems to confirm things are the same), `if` is used when you want to do something OR do something else. You use `when` only when there is no `OR do something else` and/or when there is multiple things you want to do inside.

pvinis 7y ago
It's interesting to see how you use your if and when in your sentences. Surprisingly, you have an if without an else, and a when with an or at the end! :p I do remember that convention though, and it makes sense. I just found your usages in text interesting.
- diggan 7y ago
  Haha, you're right! Re-reading my own comment, I seem to switch context between "normal language" conditionals where the rules obviously are different from the "programming language" context where they are strictly defined. Fun observation :)

aidenn0 7y ago

When has no else and if has no explicit progn. If you need an else for a side effect then cond or if will be used. I don't think there is a consensus on which of those to use for side effect vs expression when an else is needed

arethuza 7y ago
I probably got that idea from CLtL: https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node84.html https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node84.html Very much a "stylistic preference" though! Edit: I realised that for the 6 years or so I wrote CL as part of my day job that my well thumbed copy of CLtL was by far the most referenced programming language book I have ever used (mostly falling open at either the loop or CLOS chapters). Not sure what this says about CL!

reikonomusha 7y ago

This is a style rule at Rigetti Computing: use IF or COND when the return value matters and no side effects; use WHEN, UNLESS, COND if you have side effects. (Never use IF for side effects, never use WHEN/UNLESS for return values.)