[Boost-build] Target alternatives problem

Subject: [Boost-build] Target alternatives problem
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-06-27 20:33:52

I could not find documentation for target alternatives in Boost Build 
but it had previously been explained to me on this list so I tried:

alias preprocessor_gcc
    :
         [ compile arithmetic.cpp
           : <cflags>-std=c99
           : arithmetic_gcc
         ]
   :
   toolset<gcc>
   ;

only to be met by:

C:/Programming/VersionControl/boost/tools/build/v2/build\property.jam:370: 
in property.make from module property
error: 'toolset<gcc>' is not a valid property specification
C:/Programming/VersionControl/boost/tools/build/v2/build\property-set.jam:395: 
in property-set.create-from-user-input from module property-set
C:/Programming/VersionControl/boost/tools/build/v2/build\property-set.jam:448: 
in property-set.refine-from-user-input from module property-set
C:/Programming/VersionControl/boost/tools/build/v2/build\targets.jam:1563: 
in targets.main-target-requirements from module targets
C:/Programming/VersionControl/boost/tools/build/v2/build\alias.jam:64: 
in alias from module alias
Jamfile.v2:45: in modules.load from module 
Jamfile</C:/Programming/VersionControl/boost/libs/preprocessor/test>
C:/Programming/VersionControl/boost/tools/build/v2/build\project.jam:314: in 
load-jamfile from module project
C:/Programming/VersionControl/boost/tools/build/v2/build\project.jam:62: 
in load from module project
C:/Programming/VersionControl/boost/tools/build/v2/build\project.jam:168: in 
project.find from module project
C:/Programming/VersionControl/boost/tools/build/v2\build-system.jam:570: 
in load from module build-system
C:\Programming\VersionControl\boost\tools\build\v2/kernel\modules.jam:283: 
in import from module modules
C:\Programming\VersionControl\boost\tools\build\v2\kernel\bootstrap.jam:142: 
in boost-build from module
C:\Programming\VersionControl\boost\boost-build.jam:17: in module scope 
from module

What have I done wrong this time ?