ConTeXt / e-TeX Real Numbers?

Question

I've been using LaTeX for about 6 years and the calc package for a long time. Therefore, not being able to use real / floating point numbers was never really a problem.

I've been pouring over the documentation of ConTeXt for the last few days, but haven't seeing if they've decided to address this. It appears that Lua is probably the answer, but I'm just trying to fight my way through ConTeXt, at this point.

Is there an e-TeX or ConTeXt way to deal with this? I think the answer is no, but I thought I'd try. :)

Answer 1

Current ConTeXt code uses \dimexpr and \numexpr from e-TeX a lot, because most of ConTeXt predates luatex.

If you want to do a quick calculation in lua, you can just do something trivial like this:

\def\evaluate#1{\directlua{tex.sprint(tostring(#1))}}

then you can write:

\evaluate{10.2+1e6}
\evaluate{10.2/0}

et cetera.

Best wishes, Taco

Answer 2

e-TeX can evaluate simple fixed-point expressions via \dimexpr, but as you already stated, for ConTeXt Mk IV programming in Lua is the way to go, and it is much nicer, simpler and cleaner than anything TeX could ever offer.

Answer 3

Here is a simple port of the first four functions of fp-basic.sty

\unprotect
\def\FPadd#1#2#3% #1 = #2 + #3
  {\ctxlua{context.setvalue("\strippedcsname#1", #2+#3)}}

\def\FPsub#1#2#3% #1 = #2 - #3
  {\ctxlua{context.setvalue("\strippedcsname#1", #2-#3)}}

\def\FPmul#1#2#3% #1 = #2 * #3
  {\ctxlua{context.setvalue("\strippedcsname#1", #2*#3)}}

\def\FPdiv#1#2#3% #1 = #2 / #3
  {\ctxlua{context.setvalue("\strippedcsname#1", #2/#3)}}
\protect

Other functions can be defined in a similar manner, if needed. As a bonus, this works for any number format (1e6, etc) that is recognized by lua. There are no error checks, so division by zero gives inf. For example:

\starttext
\FPadd\ADD{10.2}{1e6}
\FPsub\SUB{10.2}{13.5}
\FPmul\MUL{10.2}{13.5}
\FPdiv\DIV{10.2}{0}

\startlines
\ADD
\SUB
\MUL
\DIV
\stoplines
\stoptext

gives

1000010.2
-3.3
137.7
inf

Answer 4

How about the pgfmath part of pgf? I know it can be used in ConTeXt, I just don't know if it will do full floating point for you. In trying to find out to what degree this would work for you I also found this link which has some other useful thoughts, especially in the comments.