[Boost-build] make more than one target with one custom command

Subject: [Boost-build] make more than one target with one custom command
From: Roman Matsybora (matsic_at_[hidden])
Date: 2015-09-28 13:02:10

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In Custom Command section of boost-build documentation there are 3 ways to use custom command: * using make rule 
* using notfile rule * using generate rule 
But all of these ways make only one target. 
If project has some procedure that generates many source files at once, how can I declare them? 
Example: 
program make_sources creates a1.cpp and a2.cpp a1.cpp and a2.cpp are not available  before build. 

main target is exe a : a1.cpp a2.cpp ; 
How to declare a1.cpp and a2.cpp targets? 

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