Search found 28 matches

by stackman
Wed Oct 24, 2012 7:17 am
Forum: Common Lisp
Topic: Binary search tree obscure code...
Replies: 5
Views: 18652

Re: Binary search tree obscure code...

Everything is fine in the code, you're just confused by what the call to a struct returns. When you eval nums at the repl, the :print-function defined by defstruct is called and returns a string of the form #<5>, where 5 is the element stored in the main node of your tree. Graham returns a string of...
by stackman
Sat Oct 20, 2012 1:54 pm
Forum: Common Lisp
Topic: strange error with mapcan and quote.
Replies: 1
Views: 4014

strange error with mapcan and quote.

I get a weird behavior with sbcl when I try the following code at the repl. (mapcan (lambda (x) (if (evenp x) '(even))) (list 1 2 3 4)) Sbcl hangs at 100% CPU without returning an error. Why do I get such a behavior? Apparently, this is related to the quote '(even). If I replace it by (list 'even), ...
by stackman
Fri Oct 19, 2012 1:38 am
Forum: Common Lisp
Topic: loop keywords
Replies: 4
Views: 9021

Re: loop keywords

Ah, I understand now. Thanks for the thorough answer.
by stackman
Thu Oct 18, 2012 1:20 am
Forum: Common Lisp
Topic: loop keywords
Replies: 4
Views: 9021

loop keywords

Hi, I see sometimes loop forms written as follows. (loop :for x :from 1 :to 10 :collect x) Why do some people prefix the loop keywords with a colon? Is this required by some implementations? The hyperspec insists on the fact that "Loop keywords are not true keywords." So why does the use o...
by stackman
Thu Oct 18, 2012 1:01 am
Forum: Common Lisp
Topic: fractional part of a number
Replies: 3
Views: 6497

Re: fractional part of a number

Thanks for the replies, this is definitely better.
by stackman
Mon Oct 15, 2012 1:35 pm
Forum: Common Lisp
Topic: fractional part of a number
Replies: 3
Views: 6497

fractional part of a number

Hi,
Is there a simple way to return the fractional part of a number in common lisp?
At the moment I am using

Code: Select all

(multiple-value-call (lambda (x y)(declare (ignore x)) y) (floor 1.5))
but this seems a bit verbose.
by stackman
Mon Oct 15, 2012 8:50 am
Forum: Common Lisp
Topic: true function
Replies: 3
Views: 6137

Re: true function

This does not give exactly the same result.

Code: Select all

CL-USER> (some 'identity (list nil "no" nil))
=> "no"
CL-USER> (notevery 'not (list nil "no" nil))
=> T
So I guess there is no builtin true function.
Anyway, thanks for the answer.
by stackman
Sat Oct 06, 2012 6:23 am
Forum: Common Lisp
Topic: true function
Replies: 3
Views: 6137

true function

Hi, is there a "true" function in Common Lisp ? I mean does there exist a function that returns t for all non nil values of its argument, and nil if its argument is nil? There are at least two "false" functions, not and null, which are strictly equivalent, but I was not able to l...