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 Re: Distinguishing display styles in math mode Andrew Parsloe <[log in to unmask]> Mon, 16 Jan 2017 23:23:43 +1300 text/plain (73 lines) On 16/01/2017 9:36 p.m., Joseph Wright wrote: > On 16/01/2017 08:19, David Carlisle wrote: >> On 16/01/2017 00:58, Andrew Parsloe wrote: >>> Only recently have I learnt to distinguish inline from display-style >>> maths mode by using \mode_if_inner:TF. It would be helpful for those of >>> us who come to expl3 programming without a good prior grounding in TeX >>> if a comment to this effect could be added to the documentation >>> (interface3.pdf). >>> >>> Andrew >> >> \mode_if_inner:TF is a wrapper around \ifinner so can't be used to >> distinguish inline from display. In fact in math \ifinner can't be used >> to detect much useful at all, the points at which tex is or is not in >> inner math mode are not usually interesting. (Unlike testing for inner >> when in vertical mode that tells you if you are in a box or on the main >> vertical list) > > Indeed, one cannot be sure that display math mode will actually be used > for any 'display' anyway. See for example the strategy used by breqn: > all typesetting is done in inline math mode, using \displaystyle where > appropriate. (Display math mode is used only for obtaining the length of > the line of text immediately preceding the 'display'.) > > Almost certainly you want to use \mathchoice (currently there is no > interface for this in expl3 beyond the primitive), though you might also > look at LuaTeX's additional primitives in this area if you are > considering a 'LuaTeX-only' solution. > > Joseph > I had forgotten \mathchoice. I'm not qualified to argue about the use of \mode_if_inner:TF beyond saying that it has correctly worked to date. *All* the cases of interest to me are of the following kind. #1 is a token list digestible by \fp_eval:n (usually with more * and parentheses than are strictly needed); #2 is a token list consisting of digits and a decimal point (in fact the rounded decimal number resulting from the fp evaluation of #1). Andrew \documentclass{article} \usepackage{expl3,xparse,amsmath} \begin{document} \ExplSyntaxOn \DeclareDocumentCommand \testinner { m m }    {      \mode_if_inner:TF        { \mbox{#1} \to\quad { #2 } }        { \begin{aligned} \mbox{#1} & \to \\ & { #2 } \\ \end{aligned}        }    } \ExplSyntaxOff This is an inline $\testinner { 2*sin(pi/12)*cos(pi/12) } {2\sin(\pi/12)\cos(\pi/12)=0.5 }$ expression. This is a $\testinner { 2*sin(pi/12)*cos(pi/12) } { 2\sin(\pi/12)\cos(\pi/12)=0.5 }$display-style expression. \end{document} --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus