signbit() and other true/false functions

[Michael D. Godfrey]

John,

I expect that you have seen bug #38291, which was my fault.
I used signbit(x) ==1  when I should have used signbit(x) !=0

But, is it generally true that the set of "truth-value" functions
return 0 for false and "anything else" for true?

It may seem a bit obsessive but I think it would be more
robust if the result were 0/1 and, of course, the same on
all platforms.  I would still say that the documentation should
make clear that the appropriate test should be with respect to
0.

Anyhow, I admit that my use of == 1 was simply an error.
Sorry.

Michael