“aligned” environment gives too much horizontal space

Question

I am using the aligned environment to typeset some mathematical equations. Background was discussed here: Vertical alignment in lists when using multline. The idea is to typeset equations on the same line with text.

Now, I want to align equations by more than one position. aligned gives me too much space around =:

As you can see, there is too much space between AA and =.

Here is my MWE:

\documentclass{article}
\usepackage{mathtools}

\begin{document}

$\begin{aligned}
&AA &&= a\\
&B  &&= b
\end{aligned}$

\end{document}

Answer 1

You can use alignedat if you do not want space between each equation

\documentclass{article}
\usepackage{mathtools}

\begin{document}

$\begin{alignedat}{2}
&AA &&= a\\
&B &&=b
\end{alignedat}$

\end{document}

the form with aligned is modelled on setting

a=1 b=2

with some space between each equation, so you have the right hand side of two equations, with space between.

Answer 2

Another possibility is using the array environment:

\documentclass{article}
\usepackage{mathtools}

\begin{document}

$\begin{array}{l@{{}={}}l}
AA & a\\
B  & b
\end{array}$

\end{document}

with the required result: