sign may well be a useful function, but hardly much to do with fp. chris > On 10 Mar 2017, at 16:49, Bruno Le Floch <[log in to unmask]> wrote: > > On 03/09/2017 05:42 PM, Andrew Parsloe wrote: >> Two functions which I think could be beneficially added to l3fp without >> straining its role as a kernel module (in the way that, say, the gamma >> function would) are the signature function (sgn) and a unit step >> function (Heaviside? -- the difficulty is what value to assign at 0). >> Given the numerical values assigned to true and false in l3fp, it is >> easy to mimic these with simple inequalities (e.g. (#1 > 0) - (#1 < 0) >> for sgn) but perhaps the functions should be there in the first place? >> >> I found myself wanting these when considering a table of fp values where >> it made sense to blank cells containing negative values which "got in >> the way". The code creating the table contained the option of blanking >> zero-value cells, so I multiplied the tabulated formula by 1 - (#1 < 0). >> >> Andrew >> >> --- >> This email has been checked for viruses by Avast antivirus software. >> https://www.avast.com/antivirus > > Will copied your message to https://github.com/latex3/latex3/issues/346 > and replied there that > >> sign() or sgn() definitely makes sense to me, but I’m not sure about >> step() / heaviside() / whatever. Can you give another example for the >> use case there? > > I'm adding sign(). I don't think heaviside is needed: (#1) > 0 ? (#1) : > 0 seems to do what you want pretty nicely. > > What do you think? > > Concerning Gamma, the main reason I haven't implemented it yet is that > it requires determining some magic constants that were only given to me > for a lower precision than what I need (10 digits instead of 16). > > Bruno