4 ms·

Why do you say LET and LET* have very different uses? I just use LET* if I need to reference a preceding variable in the same declaration (it happens). Actually

by gruseom 16y ago

Why do you say LET and LET* have very different uses? I just use LET* if I need to reference a preceding variable in the same declaration (it happens). Actually I vaguely remember PG in one of his Lisp books saying LET* indicates bad code, something I never understood, though empirically I've noticed some evidence for it.

jpr 16y ago
> LET* indicates bad code, something I never understood Neither did I, until I encountered something along the lines of: (let* ((foo ...) (foo ...) (foo ...) (foo ...) (foo ...) (foo ...) (foo ...)) ...)
- gruseom 16y ago
  That's strangely unidiomatic. I wonder why that person didn't just write: (let ((foo ...)) (setf foo ...) (setf foo ...) ...) On a tangential note, while I try to avoid multiple assignment as much as possible, I also enjoy availing myself of CL's imperativeness whenever doing so makes my code smaller or more efficient. I really like CL's multiparadigm approach. The sweet spot seems to be: allow side-effects in the small (i.e. within functions or small scopes) and be as strict as you can in composing larger pieces.
yewweitan 16y ago
Well, maybe 'very different' was an overstatement =). One way to look at it is that we should use single-use functions as far as possible to keep code straightforward. And as jpr said, LET* can potentially promote bad style, giving one the inclination to mix functional and imperative styles in a potentially troublesome fashion. I think it was in 'On Lisp' that PG said that use of LET* should be minimised for the reasons above. But if not, you're right. Use LET* just as you mentioned, but don't use LET* for all cases. Some discussion available @ Stack Overflow: http://stackoverflow.com/questions/554949/let-versus-let-in-common-lisp http://stackoverflow.com/questions/554949/let-versus-let-in-...

by gruseom 16y ago

jpr 16y ago

> LET* indicates bad code, something I never understood Neither did I, until I encountered something along the lines of: (let* ((foo ...) (foo ...) (foo ...) (foo ...) (foo ...) (foo ...) (foo ...)) ...)

gruseom 16y ago
That's strangely unidiomatic. I wonder why that person didn't just write: (let ((foo ...)) (setf foo ...) (setf foo ...) ...) On a tangential note, while I try to avoid multiple assignment as much as possible, I also enjoy availing myself of CL's imperativeness whenever doing so makes my code smaller or more efficient. I really like CL's multiparadigm approach. The sweet spot seems to be: allow side-effects in the small (i.e. within functions or small scopes) and be as strict as you can in composing larger pieces.

yewweitan 16y ago

Well, maybe 'very different' was an overstatement =). One way to look at it is that we should use single-use functions as far as possible to keep code straightforward. And as jpr said, LET* can potentially promote bad style, giving one the inclination to mix functional and imperative styles in a potentially troublesome fashion. I think it was in 'On Lisp' that PG said that use of LET* should be minimised for the reasons above. But if not, you're right. Use LET* just as you mentioned, but don't use LET* for all cases. Some discussion available @ Stack Overflow: http://stackoverflow.com/questions/554949/let-versus-let-in-common-lisp http://stackoverflow.com/questions/554949/let-versus-let-in-...