You can use \show
or \meaning
to see individual commands but I usually have latex.ltx
in my emacs (editor) buffer, you can find your copy with kpsewhich (or just look in the log of any latex file for the file path to article.cls
etc)
On my system
$ kpsewhich latex.ltx
/usr/local/texlive/2014/texmf-dist/tex/latex/base/latex.ltx
At line 1308 you see
\DeclareRobustCommand\hspace{\@ifstar\@hspacer\@hspace}
\def\@hspace#1{\hskip #1\relax}
\def\@hspacer#1{\vrule \@width\z@\nobreak
\hskip #1\hskip \z@skip}
searching in the file will show that \hspace
does not appear except in those lines so no command defined in the format uses \hspace
in its definition.
You can also see a typeset pdf version of the same by going
texdoc source2e
\hspace
or the primitive\hskip
code being used for arbitrary spacing. – Joseph Wright♦ Oct 7 '14 at 12:35\hspace
' can be interpreted as meaning 'Which commands use\hspace
internally?' while you mean 'How is\hspace
implemented?' or similar. – Joseph Wright♦ Oct 7 '14 at 12:57