On Tue, 22 Dec 2015, Alan BRASLAU wrote:
Wolfgang,
Can you explain to us why it should be preferable for ConTeXt users to employ \frac12 rather than the native TeX construction {1\over 2}? I understand that the macro \frac does some additional trickery but the two constructions should *always* yield identical results (when keyed-in properly).
One of the troubles with { .... \over ...} and the like is that TeX does not know which "style" to use. This can lead to extra processing when using any command defined using \mathpalatte (such as \text, stacked arrows, and others). Consider \text{...}. Basically, we want \text{...} to typeset it's argument in a \hbox with textsize equal to the normalsize in normal mode and equal to script size when used in a subscript and in scriptsciptsize when used in a sub-subscript. Now, in traditional tex, when parsing {\text{hello} \over 2} TeX does not kow what size to use for \text{...} until it encounters the \over. So, when parsing \text{hello}, TeX generates all possible sizes and then prunes them later on. With nested constructs like {\text{hello}_{\text{world} \over 2} \over 2} it can lead to exponential number of branches. With \frac{\text{hello}}{2}, TeX "knows" what style to use for the arguments. So, extra processing is not needed (at least, this is the idea in LuaTeX; in PDFTeX, multiple sizes need to be generated). This can lead to some slightly faster processing. Also see http://tex.stackexchange.com/a/1261/ answer from Taco. Contrast the definition of \cramped given there from one in the LaTeX mathtools package (http://ctan.bppro.ca/macros/latex/contrib/mathtools/mathtools.dtx) [search from MT_cramped_clap_internal:Nn] Aditya