On 04/02/2017 12:09 AM, Andrew Parsloe wrote: > Is there a simple way to distinguish -0 from 0 in l3fp? > > I had been aligning left in a table a column of sines, +0 or -0 followed > by decimal point & digits. By adding an \hphantom{-} before the positive > numbers, they aligned nicely on the decimal point in the column, but > then along came -0. The simple conditional, "if !(number < 0) add > phantom", added the phantom and the column aligned like > 0 > 0.5878 > -0 > -0.5878 > etc. > In the absence of formatted printing of numbers, -0 is a problem. Even a > built-in test for -0 would ease matters, since in any kind of formatted > printing of numbers 0 and -0 will generally require different handling. > > As it is, I've had to test each fp for whether it is zero; if it is I > convert to a tl variable and test whether that is -0. This is clumsy. > Hence my opening question. > > Andrew Sorry for the delay. One option is to normalize -0 to +0 by adding +0. Namely, number+0 is equal to number for any non-zero number and is +0 for both +0 and -0. Another option is to compute 1/number after disabling the "division-by-zero" trap, and test whether that's +inf or -inf, but that's more complicated than the tl test you're doing. A better option is that I should add a "copysign" function, that is in the IEEE standard: copysign(1,x) gives +1 or -1 depending on the sign bit of x (so in particular this distinguishes +0 and -0). For your specific use case I would use \fp_to_tl:n then test whether the first character (\str_head:n) is "-" or not. This also covers nan properly. Bruno