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Subject: Re: [Boost-build] Using variable modifiers problem
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2017-02-20 02:44:42


On 02/19/2017 07:02 PM, Edward Diener via Boost-build wrote:
> <snip>Let us say I pass:
> <toolset-msvc:version>
> to the feature.values rule. This then resolves to:
> return $(<toolset-msvc:version>.values)


> What is '<toolset-msvc:version>.values' and how does that get resolved ?
> I know my questions seem easy to someone who understands what is
> happening in jam code, but although I think I understand the language I
> am still baffled by its use and trying to figure out what it is doing. I
> would assume that '<toolset-msvc:version>.values' would be the name of
> some variable, but I cannot find any such variable name in the Boost
> Build jam files.

It's set in feature.extend-feature:
    $(feature).values += $(values) ;

In general
  map.$(key) = value ;
  result = $(map.$(key)) ;
is the idiomatic way to express a map in Jam.
In this case, feature.jam is using a postfix instead
of a prefix to identify the map, but it's essentially
the same.

In Christ,
Steven Watanabe

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