# Embedded parentheses giving the error: ! Missing { inserted.

I'm getting the above error and I can't figure out why. Here's the offending code.

t\left(2^\left(m+1\right) \right)

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Welcome to TeX.sx! – Kurt Oct 27 '12 at 22:54
Thank you! Nice people around here. – Jon Aird Oct 28 '12 at 22:44

## 1 Answer

You are just passing the token \left to the superscript, you need to pass it the whole sub-expression using a { } group:

$t\left(2^{\left(m+1\right) }\right)$


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Thanks, that makes sense. – Jon Aird Oct 27 '12 at 22:55
The solution certainly makes sense. Could someone explain to me what the error message means? Is it saying that TeX detected a problem because the argument to ^ was merely \left, and somehow it knew that was wrong? So TeX went ahead and inserted a { there, but didn't know where to put the }? I guess the "inserted" part of the error message is what confuses me the most. Why would TeX bother to insert a { if it's just going to fail with a fatal error anyway? – LarsH Jul 9 '13 at 18:39
@LarsH your description is correct,apart from the fact that errors are not fatal you have the chance to interact with them as you go along. For example you can respond i} to insert a matching close brace and the document will then complete without further error. – David Carlisle Jul 9 '13 at 20:29
Thanks, I wondered if it was something of that sort. We don't use that kind of model much these days, do we? I mean, where the processor runs into an error, and can't continue as is, but allows you to intervene, and then it can keep going without starting over. – LarsH Jul 9 '13 at 20:32
@LarsH No but when it was taking 15 minutes per page, getting to the end and then fixing as many errors as possible before starting over was a big win. – David Carlisle Jul 9 '13 at 20:34