This is a public-interest question.
The title of the question Why does this error keep popping up even though I clearly fixed it? poignantly expresses a fundamental truth of LaTeX usage: sometimes the error message just does not mean what it says. It is possible to get more information from TeX, but this operates at the lowest level possible: basic command-line interaction. No amount of this can make clear what went wrong conceptually.
Particularly insidious in this regard are environments that function as enormous macros, because the error is not reported at the line where it occurs but at the \end{}
tag, where all the processing is done (of course, this can happen with a macro that takes huge arguments, but you hardly ever see those). For example, no useful diagnostics can ever be extracted from amsmath
's align
environment, because it measures its entire contents before typesetting them a second time at the end.
I think it would be useful to gather a (necessarily anecdotal and incomplete) list of frequently-occurring error messages issued by such environments and their interpretations. Specifically, I'm looking for answers of the form:
An environment.
A misleading error message produced by that environment, particularly one with useless line information.
Typical input producing that error along with a useful description of what's wrong.
An explanation of how the error in the input leads to an antinomy in TeX's processing that produces the message given.
I'll lead off with an explanation of the error in the first question I linked, as an example.
amsmath
constructs, there's a nice list of error messages, with explanations, in the section 10 of the user manual --texdoc amsldoc
. – barbara beeton May 11 '13 at 20:12missing number
issues, but actually doesn't explain the one in the question. – Ryan Reich May 11 '13 at 20:18amsmath
documentation will be updated when the macros undergo an overhaul (not yet scheduled), and if something is missing, it would be helpful to have a good list of items that need to be addressed. – barbara beeton May 11 '13 at 20:30missing } inserted
given among the errors in the manual. – Ryan Reich May 11 '13 at 20:35missing }
also happens if a$
gets intoeqnarray
, so it's not justamsmath
. but i'll put it on the list. – barbara beeton May 11 '13 at 20:42