Perforce Jam incompatibility

From: David Abrahams (dave_at_[hidden])
Date: 2002-11-15 18:59:51

I was just looking over Rene's new document at
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/*checkout*/boost/boost/tools/build/jam_src/readme.html,
which says,

"It contains significant improvements made to facilitate its use in
the Boost Build System, but should be backward compatible with
Perforce Jam"

Well, we have one known backwards(?)-incompatibility:

When Perforce introduced rule indirection, they did it a bit
differently than we did:

x = a b ;
y = [ $(x) c d ] ;

In Boost.Jam, this is equivalent to:

y = [ a b c d ] ;

In Perforce Jam, this is equivalent to:

a c d ;
y = [ b c d ] ;

Either behavior can be built in terms of the other, but I thought the
Boost.Jam behavior was more-useful, and we were there first, so I
didn't change it when Perforce added rule indirection. I don't know if
that was a bad choice. However, we ought to decide whether to keep
that difference, and if so, how to document it.

-Dave

-- 
David Abrahams
dave_at_[hidden] * http://www.boost-consulting.com
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