Alex assumes tab to be size 8 about alex

[simonmar]

Tabs are size 8 in Haskell, see the Haskell report.

[osa1]

How is this related with tab sizes in Haskell report? \t is one character but Alex behaves as if it's 8 characters.

[chamini2]

Maybe a flag for --tab-size=NUMBER that defaults to 8 can be added. I guess that would be done by adding a State Monad in the ParseMonad module.

[simonmar]

Alex adopts the same convention for .x files as for Haskell, which is that tab stops are 8 columns apart. If you don't like this, you don't have to use tabs (in fact, it's better just not to use tabs anyway).

Now, in the generated lexer (rather than Alex itself) it is arguably wrong to fix the same convention: https://github.com/simonmar/alex/blob/master/templates/wrappers.hs#L151

By all means submit a pull request to change this, I suppose we could have a command line flag, and plumb the tab width through to wrappers.hs using CPP.

[chamini2]

Oh... I see my mistake. I thought the line in the ParseMonad module was for the generated lexer. That is what I meant to link. Thank you for clearing that up!

Now, in the line in the wrapper file that you linked, that one should follow the flag's instruction. I'll see to make a pull request with that change!