TeX - LaTeX Asked on July 26, 2020
This code compiles correctly as long as I don’t put spaces around arguments #3
and #4
in the definition of vec
. I can’t find anything about this in the xparse
documentation, and I have been under the impression that spaces in such places are the preferred style in LaTeX3
so I’d like to know why this happens. I have a feeling it may be trivial, but I’m not seeing it.
My MWE (contains code originally by @egreg):
documentclass{article}
usepackage{amsmath}
usepackage{xparse}
usepackage{esvect}
% A smarter vec command.
% Why doesn't it work when I put spaces around #3 or #4?
RenewDocumentCommand{vec}{ s m e{_^} }{%
ensuremath{%
IfBooleanTF {#1}
{vv{#2}}
{boldsymbol{#2}}
_{IfValueT{#3}{#3}vphantom{smash[b]{|}}}
^{IfValueT{#4}{#4}vphantom{smash[t]{big|}}}
}%
}%
begin{document}
[
vec{E}_{text{ball}}
qquad
vec{E}_{_{text{ball}}}
]
[
vec{p}_{text{ball}}
qquad
vec{p}_{_{text{ball}}}
qquad
]
[
vec{F}
qquad
vec{F}_{text{proton}}
qquad
vec{F}^{text{elec}}
qquad
vec{F}^{text{elec}}_{text{proton}}
qquad
vec{F}_{text{proton}}^{text{elec}}
]
[
vec{F}
qquad
vec{F}_{21}
qquad
vec{F}_{21}^{text{contact}}
qquad
vec{F}_{text{table on ball}}^{text{contact}}
qquad
vec{F}^{text{contact}}_{text{table on ball}}
]
end{document}
Here is the result without the spaces in question:
And here is the result WITH the spaces in question:
(continue from this comment)
An ugly workaround:
e{^_}
before ExplSyntaxOn
, in order to frozen the catcode of _
, and_
(required) and ^
(just for consistent) by their command form sb
(sub-script) and sp
(super-script), respectively.documentclass{article}
usepackage{amsmath}
usepackage{xparse}
usepackage{esvect}
% A smarter vec command.
% Why doesn't it work when I put spaces around #3 or #4?
deftemp{ RenewDocumentCommand{vec}{ s m e{_^} } }
ExplSyntaxOn
temp{%
ensuremath{%
IfBooleanTF {#1}
{vv{#2}}
{boldsymbol{#2}}
sb{IfValueT{ #3 }{#3}vphantom{smash[b]{|}}}
sp{IfValueT{ #4 }{#4}vphantom{smash[t]{big|}}}
}%
}%
ExplSyntaxOff
begin{document}
[
vec{E}_{text{ball}}
qquad
vec{E}_{_{text{ball}}}
]
[
vec{p}_{text{ball}}
qquad
vec{p}_{_{text{ball}}}
qquad
]
[
vec{F}
qquad
vec{F}_{text{proton}}
qquad
vec{F}^{text{elec}}
qquad
vec{F}^{text{elec}}_{text{proton}}
qquad
vec{F}_{text{proton}}^{text{elec}}
]
[
vec{F}
qquad
vec{F}_{21}
qquad
vec{F}_{21}^{text{contact}}
qquad
vec{F}_{text{table on ball}}^{text{contact}}
qquad
vec{F}^{text{contact}}_{text{table on ball}}
]
end{document}
Correct answer by muzimuzhi Z on July 26, 2020
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