bug#10327: Please document include and include-from-path

[Andy Wingo <wingo@pobox.com>]

Hello Ian & Ian :)

Thanks for the report.  I added some extensive docs.

    6.17.11 Local Inclusion
    -----------------------

    This section has discussed various means of linking Scheme code
    together: fundamentally, loading up files at run-time using `load' and
    `load-compiled'.  Guile provides another option to compose parts of
    programs together at expansion-time instead of at run-time.

     -- Scheme Syntax: include file-name
         Open FILE-NAME, at expansion-time, and read the Scheme forms that
         it contains, splicing them into the location of the `include',
         within a `begin'.

       If you are a C programmer, if `load' in Scheme is like `dlopen' in
    C, consider `include' to be like the C preprocessor's `#include'.  When
    you use `include', it is as if the contents of the included file were
    typed in instead of the `include' form.

       Because the code is included at compile-time, it is available to the
    macroexpander.  Syntax definitions in the included file are available to
    later code in the form in which the `include' appears, without the need
    for `eval-when'.  (*Note Eval When::.)

       For the same reason, compiling a form that uses `include' results in
    one compilation unit, composed of multiple files.  Loading the compiled
    file is one `stat' operation for the compilation unit, instead of `2*N'
    in the case of `load' (once for each loaded source file, and once each
    corresponding compiled file, in the best case).

       Unlike `load', `include' also works within nested lexical contexts.
    It so happens that the optimizer works best within a lexical context,
    because all of the uses of bindings in a lexical context are visible,
    so composing files by including them within a `(let () ...)' can
    sometimes lead to important speed improvements.

       On the other hand, `include' does have all the disadvantages of
    early binding: once the code with the `include' is compiled, no change
    to the included file is reflected in the future behavior of the
    including form.

       Also, the particular form of `include', which requires an absolute
    path, or a path relative to the current directory at compile-time, is
    not very amenable to compiling the source in one place, but then
    installing the source to another place.  For this reason, Guile provides
    another form, `include-from-path', which looks for the source file to
    include within a load path.

     -- Scheme Syntax: include-from-path file-name
         Like `include', but instead of expecting `file-name' to be an
         absolute file name, it is expected to be a relative path to search
         in the `%load-path'.

       `include-from-path' is more useful when you want to install all of
    the source files for a package (as you should!).  It makes it possible
    to evaluate an installed file from source, instead of relying on the
    `.go' file being up to date.


On Sat 24 Dec 2011 00:53, Ian Price <ianprice90@googlemail.com> writes:

> Or am I being ever so slightly patronising?

"Recursion and condescension"? :-)

  http://james-iry.blogspot.com/2009/05/brief-incomplete-and-mostly-wrong.html

Cheers,

Andy
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