[Boost-build] Quick Q regarding feature propagation syntax

From: Kostas Kostiadis (kos_at_[hidden])
Date: 2007-01-25 10:23:05

Hello all,
 
Say I have a lib physics, that uses a lib math.
Also, say that the math lib has a "feature" <use_doubles_instead_of_floats>
with possible values no/yes, defaulting to no.
 
In my main project jamfile, I can do something like:
 
use-project /physics : /some/path/physics ;
 
exe foo
    :
        main.cpp
        /physics/<use_doubles_instead_of_floats>yes
    :
    ;
 
 
NOTE: The use_doubles_instead_of_floats feature is a feature in the math lib
NOT the physics lib.
 
How can I propagate this feature to the math lib?
Should I be using the math lib directly into the main project's jamfile?
i.e.
 
use-project /physics : /some/path/physics ;
use-project /math : /some/path/math ;
 
exe foo
    :
        main.cpp
        /physics
        /math/<use_doubles_instead_of_floats>yes
    :
    ;
 
I don't really need to do this, because physics "uses" maths anyway.
 
Also, what is the syntax if I have multiple features for a given lib? Can I
do:
 
exe foo
    :
        main.cpp
        /someLib/<feature1>on/<feature2>off/<someOtherFeature>yes
    :
    ;
 
 
Your help much appreciated.
 
cheers,
K.