Re: Standard library praise and challenge
- Posted by bill Sep 14, 2011
- 3190 views
One can say {} is the empty sequence. True.
However that is not the case when you are comparing atoms. {} has no atom, nothing, NULL. Hence when the sequence is flattened the empty sub-sequences disappear (just as in SQL, NULLs are ignored).
It leaves the problem of what to do with max(NULL) and min(NULL). They should return nothing ({} or NAN). It is odd to call it an error since this would imply that min({{},1}) should also be an error as it is saying:
"which is smaller nothing or 1?"
Note the (inconsistent) treatment of NULL by compare:
include std/math.e 1: ? compare(MINF,MINF) 0 2: ? compare(MINF,min({})) -1 * 3: ? compare(MINF,max({})) 0 ** 4: ? compare(MINF,PINF) -1 5: ? compare(min({}),MINF) 1 * 6: ? compare(min({}),min({}) 0 7: ? compare(min({}),max({})) 1 ** 8: ? compare(min({}),PINF) 0 ** 9: ? compare(max({}),MINF) 0 ** 10: ? compare(max({}),min({})) -1 ** 11: ? compare(max({}),max({})) 0 12: ? compare(max({}),PINF) 0 * 13: ? compare(PINF,MINF) 1 14: ? compare(PINF,min({})) 0 ** 15: ? compare(PINF,max({})) 1 * 16: ? compare(PINF,PINF) 0
