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(guile-tut.info)Two world views

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Two world views
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  In this manual, I usually jump into examples and explain them as you
type in the code; here I will digress and ramble for a few paragraphs to
set some concepts straight, and then let you type (or paste) in fun
examples.

  In 1995, I implemented a large program, "Gnudl", using Guile quite
extensively.  In the design phase of Gnudl, I found I had to make a
choice: should the fundamental data structures be C or Scheme data
structures?

  Guile allows C to see its data structures (scalar types, lists,
vectors, strings ...).  C also allows Guile to see its data structures.
As a large program designer, you have to decide which of those
capabilities to use.  You have two main choices:

  1. You can write your software mostly in Scheme.  In this case, your C
     software will mostly parse the Scheme code with Guile calls, and
     provide some new primitive procedures to be used by Scheme.  This
     is what Gnudl does.

  2. You can write your software mostly in C, occasionally allowing
     Scheme code to be parsed by Guile, either to allow the user to
     modify data structures, or to parse a configuration file, ...

  Mixing the two approaches seems unwise: the overall layout would be
confusing.  But who knows?  There might be problems that are best solved
by a hybrid approach.  Please let me know if you think of such a
problem.

  If you use the former approach, we will say that the "master world"
is Scheme, and the C routines serve Scheme and access Scheme data
structures.  In the latter case, the master world is C, and Scheme
routines serve the C code and access C data structures.

  In both approaches the `libguile.a' library is the same, but a
predominantly different set of routines will be used.  When we go
through examples of libguile use, we will point out which is the master
world in order to clarify these two approaches.