Conditional requirements

From: Vladimir Prus (ghost_at_[hidden])
Date: 2003-07-18 09:17:27

Hello,
I'd like to tighten up the rules for conditional requirements. 

Consider:

exe a : a.cpp : 
<variant>debug:<optimization>speed 
<optimization>off:<define>USE_SLOW_BUT_TESTED_ALGORITHM
;

Now, someone just calls "bjam" and "a" will be built with default properties:
"<variant>debug <optimization>off". Requirements are evaluated and the result 
is that <optimization>speed is used and <define>USE_SLOW_BUT_TESTED_ALGORITHM
is added.

And that's confusing! I'd expect the target to be build either with 
<optimization>speed or <optimization>off and <define> to appear only in 
second case. But the target is build with <optimization>off and <define>.
IOW, one conditional requirements changes property used as condition for 
another. 

I think the simplest solution is to declare that in conditional property, part 
after ":" can be only free or incidental, and that free/incidental features 
cannot be present before ":". Opinions? Anybody using non-free conditional 
properties?

- Volodya