> I had the experience recently of checking a complicated trigonometric > expression derived, after an embarrassingly long labour, from another > complicated trigonometric expression. Had I made a mistake in the > working? I evaluated the expressions using l3fp. One, for a number of > different parameter values gave 0, the other for the same parameter > values gave -0. I concluded, ruefully, that the derivation was correct. Note that \fp_compare:nTF { 0 = -0 } { true } { false } gives true, so you could just let l3fp compare the numbers. I have to say I'm surprised by that use of l3fp: I'd definitely use a general purpose programming language for that (e.g., python). Happy l3fp helps. > To someone, like me, not versed in numerical analysis, the occurrence of > signed zero was a surprise. The 0+x trick is good to know and perhaps > worth mentioning in the documentation. I'm not keen on mentioning it in the documentation, as it is a trick indeed. Instead, I've moved "customized formatting of floating points" (e.g. with a printf-like syntax) up in my todo list. I have some ideas there. Bruno