. Do not try to build the generator too soon: wait until you have the modeling
language, an example model, and the correct output to be generated from that
model.
308 GENERATOR DEFINITION
Making a proper code generator is de?¬?nitely worth the effort. A sizable proportion
of the productivity bene?¬?ts ofDSMare due to the generator, and in particular its ability
to turn the declaratively speci?¬?ed solution from the models into the procedural form
required by most of today??™s programming languages. While in theory, and sometimes
in practice, it is possible to interpret the declarative form at runtime, performance
constraints tend to rule this out. This is no surprise: when we moved from machine
code to Assembler, or Assembler to 3GLs, the majority of languages chose to
transform the newer form to the older once at compile time, rather than continually at
runtime.
The different types of generator facilities have their strengths and weaknesses. The
sweet spot at the moment seems to be crawlers, which offer more power than model
visitors or templates, while keeping the generator on a higher level of abstraction than
the model API approach. More advanced template languages are also a good choice,
especially where they are integrated in theDSMtool. Solutions that involve a separate
generator program will always incur the additional cost of outputting the model in a
format the generator can read, and parsing that format to rebuild the model structures
on which the generator will work.
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