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I am using the Neo keyboard layout, which uses all kinds of modifier keys to input all kinds of characters (e.g. Greek letters and mathematical symbols). It also has shift+Mod3+space mapped to Unicode 0A, no-break space. From time to time it happens that I mistakenly press these buttons (while entering a space between other symbols with the same modifier keys).

Unfortunately [Lua|Xe]TeX obeys these spaces as unbreakable spaces both in normal text and in mathmode (using fontspec and unicode-math). However my editor (vim) shows the symbol like a normal space, so it is impossible to see where I made a mistake.

Is there an easy way to tell [Lua|Xe]TeX to treat no-break spaces like normal spaces?

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up vote 11 down vote accepted
\newunicodechar{ }{ }

In the first argument you put a NO-BREAK SPACE (U+00A0), in the second a normal space. A better definition would be

\newunicodechar{ }{~}

(again the space is NO-BREAK SPACE), so this unbreakable space will stretch or shrink wit the other spaces in the line. Of course use the first one if you want a normal space, ça va sans dire. :)

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Another solution will be to change vim setup so that you can see the non-breakable space.

set listchars=nbsp:¬
set list

You can set appropriate syntax highlighting for NonText to highlight the non-breakable space.

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Great. Though I'll use ␣, as it has less chance of being actually used in the (math) text. – Caramdir May 16 '11 at 22:15

Sometimes you might want to use an actual no-break space. So turning them into normal spaces altogether might not be the best idea. In that case Adityas solution is a good start. But I don’t like my indentation displayed as ^I.

The following colours the no-break spaces in gvim:

hi NoBreakSpace guibg=LightGoldenrod1 guifg=black
syn match NoBreakSpace / / containedin=ALL
syn match NoBreakSpace / / containedin=ALL

You can also do something similar to set list by using the conceal feature and replace the displayed character in normal mode with

hi Conceal guibg=LightGoldenrod1 guifg=black
syn match WhiteSpace / / containedin=ALL conceal cchar=⍽
syn match WhiteSpace / / containedin=ALL conceal cchar=¦
setl conceallevel=2 concealcursor=nv

in .vim/after/ftplugin/tex/<somename>.vim.

This will also display $\alpha^{+1}$ as α⁺¹. If you don’t like these other concealments you can disable them with

let g:tex_conceal = ""

in your .vimrc. Compare :help tex-conceal.

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You can also do the following:

Go into Command mode in vim by hitting ESC, so what you enter appears in a special command-line at the bottom of the screen.


Enter / directly followed by what you want to search for and hit enter to search in forward direction.

To search in backwards direction, use ? instead of /.

To repeat the search in forward direction just hit n and to repeat the search in backwards direction, hit N.

To have the searchresults highlighted use :set hls (high-light search) or add set hls to your vimrc to switch it on permanently.


Again in command mode the syntax is: :[where] s/Searchpattern/Substitution/[Flags]

:22,150 s/a/z/ c this substitutes (the first appearance of) a with z from line 22 to 150 and the c at the end means, that vim will ask you each time before applying the substitution.

:1,$ s/a/z/ a will make the same substitution from the first to the last line of the document and the a at the end means to substitute without asking.

:% s/a/z/ g % is a shortcut for 1,$ and g means that vim will apply the substitution globally — substitute all appearances it finds in a line, else it might only substitute the first appearance.

These regular expressions are utterly powerful.

To find out more about this try :help substitute (you can leave the help via :q).

:set hls

:%s/ / /gc

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