[Boost-docs] [quickbook] Template argument evaluation.

Subject: [Boost-docs] [quickbook] Template argument evaluation.
From: Daniel James (daniel_james_at_[hidden])
Date: 2009-05-26 22:16:29

Hi,

I've been going through some of the old template tickets, and having a
look at the implementation and there's a few things which could be
improved. I think that these changes should be activated by a version
switch, so perhaps it's worth starting on a version 1.5.

First, quickbook currently uses dynamic scoping which is generally
accepted to be a bad idea. So I'd like to change it to use static
scoping. This example:

    [template x static scoping]
    [template foo1[] [x]]
    [template foo2[x] foo1]
    [foo2[dynamic scoping]]

Will currently return 'dynamic scoping', I'd like it to change it to
return 'static scoping' for 1.5 or whatever.

When template arguments are expanded they are evaluated with the
current scope rather than the scope they were called with which can be
surprising. So I'd like to change it so that they are bound to the
correct scope. So:

   [template x new]
   [template foo1[a x] [a]]
   [foo1 [x] old]

Will return 'old' at the moment, I'd prefer it to return 'new'.
Another way to achieve this would be to evaluate template arguments
eagerly but that would be a much bigger change and harder to implement
a version switch for. This change will fix this ticket:
https://svn.boost.org/trac/boost/ticket/2034

Does this sound okay?

Daniel