Bug in evaluating "if(p==[],...)"

[Gottfried Helms <Gottfried.Helms@t-online.de>]

This is a funny bug.

I have a function with two arguments (p,q);
 - if in argument p is a scalar value, a vector in q is expected,
 - if in p is a vector, in q is a scalar expected.
 The vectors can be empty (p=[] or q=[]), their type being vector
 simply indicates, that some specific sequel has to be worked.


Here is the maximally reduced function:

{testfindroots_pq(p=[],q=[]) = my();
    if(p==[]
       ,print("p=",p," q=",q," ---> heading in p==[] path  ");
       ,print("p=",p," q=",q," ---> heading in p<>[] path  ");
      ); }


Here the result:

testfindroots_pq([],1) \\ p=[] q=1 ---> heading in p==[] path        +++ correct
testfindroots_pq([],0) \\ p=[] q=0 ---> heading in p==[] path        +++ correct

testfindroots_pq(1,[]) \\ p=1 q=[] ---> heading in p<>[] path        +++ correct
testfindroots_pq(0,[]) \\ p=0 q=[] ---> heading in p==[] path        ***** false *****

The problem is here, that supplying the scalar integer value "0" is
taken as "==[]" (but not for instance the integer value "1")

Just to note for this tiny bug.

-----------------------------------------------------------------------------------

A correctly working version is of course the more explicite

{testfindroots_pq(p=[],q=[]) = my();
   if(type(p)=="t_VEC"  \\ <-- this works correctly
       ,print("p=",p," q=",q," ---> heading in p==[] path ");
       ,print("p=",p," q=",q," ---> heading in p<>[] path ");
     ); }

Gottfried Helms