What to do with this hyperref note on amsmath?

Question

http://www.ctan.org/tex-archive/macros/latex/contrib/hyperref/ has this note copied below:

amsmath
-------------
The environments equation and eqnarray are not supported too well. For example, there might be spacing problems (eqnarray isn't recommended anyway, see CTAN:info/l2tabu/, the situation for equation is unclear, because nobody is interested in investigating). Consider using the environments that package amsmath provide, e.g. gather for equation. The environment equation can even redefined to use gather:

\usepackage{amsmath}
\let\equation\gather
\let\endequation\endgather`

However, gather and equation environment have the spacing difference as in the answer by Will in align vs equation. Thus my question:

In a document using both hyperref and amsmath, what is the best replacement for equation?

Answer 1

You can see a spacing problem with the following example. The two equations have different spacing with hyperref, but the same spacing (as they should) without it:

\documentclass[fleqn]{article}

\usepackage{amsmath}
\usepackage{hyperref}

\begin{document}

This is a test to check the spacing of the equation environment. Too much?
\begin{equation}
a=b
\end{equation}
This is a test to check the spacing of the equation environment.

This is a test to check the spacing of the equation environment. Too much?%
\begin{equation}
a=b
\end{equation}
This is a test to check the spacing of the equation environment.

\end{document} 

But this problem is imo not enough to stop using the equation environment. The other math environments produce too much space if the sentence before the displayed math is short:

\documentclass{article}

\usepackage{amsmath}

\begin{document}

This is a test to check the spacing of the equation environment. Too much? Foo.
\begin{equation}
a=b
\end{equation}
This is a test to check the spacing of the equation environment.

This is a test to check the spacing of the align environment. Too much? Foo.
\begin{align}
a=b
\end{align}
This is a test to check the spacing of the align environment.

\end{document} 

which is a much more common problem.

Answer 2

i'm writing on behalf of the maintainers of amsmath. we do maintain a list of bugs reported for both amsmath and friends and the ams document classes, and are now actively examining the list in preparation for an upgrade of the entire collection.

the spacing problem mentioned in this thread appears to be a bug, though not identical to any that have already been reported (a vertical spacing mismatch between equation and multline is on our list), so this example will be examined and added to the list if verified.

Update:

Maintenance of this package was transferred to the LaTeX Project team in 2016. Bug reports can be opened (category amslatex) at https://latex-project.org/bugs/.

Answer 3

Put the following code somewhere in your document preamble:

\makeatletter
\AtBeginDocument{%
  \if@fleqn%
  \let\old@equation\equation%
  \renewcommand{\equation}{\ifhmode\unskip\fi\old@equation}%
  \fi%
}
\makeatother

This should fix the vertical spacing problem that arises when using AMSLaTeX's equation environment together with the hyperref package.

Answer 4

My rule of thumb is to always use align everywhere for math. Works with hyperref just fine =)

To suppress too much whitespace do not place a double carridge-return after the environment.

bla:
\begin{align}
a^2+b^2=c^2
\end{align}
More text straight away