Btukfyl

I typeset some systems of equations, and I really like the format of input (as well as the output) the systeme package provides.

Now, I wonder if there is a way to flushright also the right-hand side of the equation, without using hphantom? In the example below, I get the result as I want in the second system, but not the first. But I do it with a hphantom.

 documentclass{minimal}

 usepackage{systeme}

 begin{document}

 [

 systeme{x+y=2,x-y=-2}

 ]

 [

 systeme{x+y=hphantom{-}2,x-y=-2}

 ]

 end{document}

giving

Update

Just in case someone wonders why on earth one would like to have the right-hand side flushright, here is an image that might explain it better. Without the right-hand side being flushright, the arrows look bad not ending at the same horizontal location.

Also, I can mention that I have read the documentation of the systeme package, and I did not find anything like this (but my french is rusty). I also browsed the source of the package, but that was too complicated for me...

It's a choice of the package to have the last column aligned left and, as far as I can see, there's no provision for changing it by setting an option.

You can change it by redefining the command SYS@makesyspreamble@i that's responsible for setting the alignment in columns; the simplest way is to use regexpatch:

documentclass{article}



usepackage{systeme}

usepackage{regexpatch}



makeatletter

xpatchcmd{SYS@makesyspreamble@i}

  {$##$hfilnull}% left alignment

  {hfil$##$null}% right alignment

  {}{}

makeatother



begin{document}



[

systeme{x+y=2,x-y=-2}

]



end{document}

Should you need to switch between left and right alignment, here's how to do it.

documentclass{article}



usepackage{systeme}

usepackage{regexpatch}



makeatletter

xpatchcmd{SYS@makesyspreamble@i}

 {$##$hfilnull}

 {spanSYSX@afterequalalignmentnull}

 {}{}

newcommand{SYSX@afterequalalignmentleft}{$##$hfil}% default

newcommand{SYSX@afterequalalignmentright}{hfil$##$}% default

newcommand{rightalignafterequal}{%

  letSYSX@afterequalalignmentSYSX@afterequalalignmentright

}

newcommand{leftalignafterequal}{%

  letSYSX@afterequalalignmentSYSX@afterequalalignmentleft

}

leftalignafterequal % default

makeatother



begin{document}



[

systeme{x+y=2,x-y=-2}

]

[

rightalignafterequal

systeme{x+y=2,x-y=-2}

]



end{document}

The rightalignafterequal declaration obeys the usual scoping rules, so you can issue it in the preamble if you want all systems to have right alignment.

How to make these arrows in the systeme?