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Que veut dire l'erreur: « Missing $ inserted » ?

  • Message: Missing $ inserted
  • Origine: TeX.

\TeX{} a rencontré quelque chose qui n'est autorisé qu'en mode mathématique (par exemple, \sum, \alpha, ^) alors qu'il était en mode texte, ou, à l'inverse, quelque chose d'interdit en mode mathématique (par exemple \par) alors qu'il traitait une formule. Il a donc inséré un $ pour passer en mode mathématique ou pour le quitter.

Par exemple si l'on essaie d'obtenir un trait de soulignement « \_ » en saisissant _ au lieu de la commande \_, \LaTeX{} composera le reste du paragraphe en mode mathématique, le plus souvent en produisant plusieurs erreurs au cours de ce traitement.


There are certain things that only work in maths mode. If your document is not in maths mode and you have an _ or a ^ character, TeX (and by inheritance, LaTeX too) will say

! Missing $ inserted

as if you couldn't possibly have misunderstood the import of what you were typing, and the only possible interpretation is that you had committed a typo in failing to enter maths mode. TeX, therefore, tries to patch things up by inserting the $ you “forgot”, so that the maths-only object will work; as often as not this will land you in further confusion.

It's not just the single-character maths sub- and superscript operators: anything that's built in or declared as a maths operation, from the simplest lower-case \alpha through the inscrutable \mathchoice primitive, and beyond, will provoke the error if misused in text mode.

LaTeX offers a command \ensuremath, which will put you in maths mode for the execution of its argument, if necessary: so if you want an \alpha in your running text, say \ensuremath{\alpha}; if the bit of running text somehow transmutes into a bit of mathematics, the \ensuremath will become a no-op, so it's pretty much always safe.


Sources:

2_programmation/erreurs/m/missing_dollar_inserted.1610295598.txt.gz · Dernière modification: 2021/01/10 17:19 par jejust
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