Does a space always belong after
pt, e.g. as used in
\hskip1pt? If a space is used, are there situations where a space will appear where it is not intended? If no space is used, will
pt be unrecognized, e.g., if a letter immediately follows, as in
By the syntax rules of TeX, any length specification allows an optional space after it which is ignored.
The space is always looked for performing macro expansion, which ends when a space or another unexpandable token is found. A space token is then ignored.
However, you should remember that a
is not equivalent to
The former will result in a
So it's best to end incomplete
The following should answer your question:
It boils down to readability of your code. In that sense, separating lengths from other document elements ("option" 2 & 4 above) makes sense.
Of course, if your editor has syntax highlighting, then perhaps you can live with all possibilities.