On 31-Aug-2012 06:25:26 Dave Kemper wrote: > Hi, > Is there a way to fetch the numeric value of a register regardless > of what output format is currently associated with the register? > > The only method I've been able to figure out is: > > .ds reigning_format \g% > .af % 0 > .nr page_number \n[%] > .af % \*[reigning_format] > > to save the format, switch it to numeric, fetch the value, and then > switch the format back to its saved status. Then I can use > \n[page_number] when I need the numeric version of the page number > (in calculations,for instance). This works, but is not very elegant. > > The existence of a better mechanism is implied by the .af documentation: > "Changing the output format of a read-only register causes an error. > It is necessary to first copy the register's value to a writeable > register, then apply the `af' request to this other register." > Unfortunately, no hint is provided on how one might copy the register's > value in a case where the register's output format cannot be changed. > The intuitive solution -- using .nr -- fails when the output format is > "i", generating the message: > > warning: numeric expression expected (got `i') > > (or "got `v'" or "got `x'", depending on the register's current value)
Given that when groff enounters (e.g.) \n% it substitutes at that point the value of \n% in its current ouitput format, I think that your "not very elegantg" solution (or equivalent) is the way to do it. However, you can sweep the inelegance under the carpet by defining a macro. For example, the following: .nr % 9 \n% \g% \" To display default format (Arabic) .br .af % i \n% \g% \" To display new format (l.c. Roman) .br .de get% \" Defines macro "get%" .ds rf \\g% .af % 1 .nr \\$1 \\n% .af % \\*[rf] .. .get% X \n[X] \g[X] \n% \g% \" To display final and original formats produces the result: 9 0 ix i 9 0 ix i And you could extend the macro to get the value from some register other than \n%, using a second argument, e.g. .de getnum .ds rf \\g[\\$1] .af \\$1 1 .nr \\$2 \\n[\\$1] .af \\$1 \\*[rf] .. so that ".getnum reg1 reg2" would put the numerical value of reg1 into reg2. Thus .getnum % Y \n[Y] \g[Y] \n% \g% produces the same result 9 0 ix i as before. Ted. ------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@wlandres.net> Date: 31-Aug-2012 Time: 10:10:01 This message was sent by XFMail -------------------------------------------------
