(and), (or), (+), (*) ...
Posted: Thu Jun 11, 2009 12:26 pm
In Newlisp
In Common Lisp:
IN Scheme:
Can I suggest change of the behaviour in Newlisp, this time I think CL and Scheme got it right, ie. result of the operation on zero arguments is neutral element for given operation. It is the most critical for and, because unilke + and *, it returns some result, but not expected one. One example from practice:
(and x1 x2 true x3 ...) = (and x1 x2 x3 ...)
Simplification of and - formula by deletion of true is typical syntactical transformation of logical formula. However, in Newlisp, the last deletition cannot be done because
(and true) =/= (and)
other interesting cases are max and min, even begin can be understood as special case.
Code: Select all
> (and)
nil
> (or)
nil
> (+)
ERR: missing argument in function +
> (*)
ERR: missing argument in function *
>Code: Select all
[1]> (or)
NIL
[2]> (and)
T
[3]> (+)
0
[4]> (*)
1Code: Select all
> (or)
#f
> (and)
#t
> (+)
0
> (*)
1
> (and x1 x2 true x3 ...) = (and x1 x2 x3 ...)
Simplification of and - formula by deletion of true is typical syntactical transformation of logical formula. However, in Newlisp, the last deletition cannot be done because
(and true) =/= (and)
other interesting cases are max and min, even begin can be understood as special case.