On 10/22/2014 09:46 PM, Gregory Ewing wrote: > Chris Angelico wrote: >> I've seen much MUCH worse... where multiple conditional >> expressions get combined arithmetically, and then the result used >> somewhere... > > In the days of old-school BASIC it was common to > exploit the fact that boolean expressions evaluated > to 0 or 1 (or -1, depending on your dialect :) to > achieve conditional expressions or other tricks.
As far as I can tell, no BASIC dialect I've looked at (DOS and Linux worlds only), has ever had any logical operators like AND (&&), OR (||), and NOT (!). They only appear to have bitwise operators (&,|,~ C equivalent). The fact that comparison operators returned 0 and -1 made the bitwise operators function the same as logical. But you can run into trouble if you tried to use a common python idiom like this: x = read_some_lines() 'returns number of lines read, or zero if none are if not x: print ("I couldn't read any lines") exit(1) Basically any value other than -1 for x would cause the not x to be true. Off topic, and no matter to python programmers. But for BASIC you need to watch out for this. One BASIC dialect introduced a set of functions, istrue() and isfalse() to convert a non-zero truth value to -1, and any falsish value to zero (like maybe an empty string). That way the bitwise operators would always function as logical operators in a conditional expression. -- https://mail.python.org/mailman/listinfo/python-list