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