Why use ''\[ ...\]'' in place of ''$$ ... $$''?

LaTeX defines inline- and display-maths commands, apparently duplicating the TeX primitive maths sequences which surround maths commands with single (or pairs of) dollar signs.

In fact, LaTeX's inline maths grouping, \( … \), has (almost) exactly the same effect as the TeX primitive version $ … $. (The exception: the LaTeX version checks to ensure you don't put \( and \) the wrong way round; this does occasionally detect errors….)

Since this is the case, one often finds LaTeX users, who have some experience of using Plain TeX, merely assuming that LaTeX's display maths grouping \[ … \] may be replaced by the TeX primitive display maths $$ … $$.

Unfortunately, the assumption is wrong: some LaTeX code needs to patch display maths, it can only do so by patching \[ and \] (or their equivalents). Most obviously, the class option fleqn simply does not work for equations coded using $$ … $$, whether you're using the standard classes alone, or using package amsmath. Also, the \[ and \] construct has code for rationalising vertical spacing in some extreme cases; that code is not provided $$ … $$, so if you use the Plain TeX version, you may occasionally observe inconsistent vertical spacing. Similar behaviour can bite if you are writing a proof; placing the “QED symbol” doesn't work if it is in $$-displayed maths.

There are more subtle effects (especially with package amsmath), and the simple rule is “use \[ … \] (at least) whenever displayed maths is needed in LaTeX”.

(Note that the sequence \[ … \] is duplicated by the displaymath environment, which can be said to “look nicer”, and actually describes what's being done.)


Source: Why use ''\[ ... \]'' in place of ''$$ ... $$''?

domaines_specialises/mathematiques/arguments_contre_les_doubles_dollars2.txt · Dernière modification: 2019/02/03 08:34 par jejust
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