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Added more words to #:replace from Ludovic. Thanks!

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Marius Vollmer 2005-12-07 00:31:49 +00:00
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33
doc/ref/api-modules.texi
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@ -456,17 +456,32 @@ will have the effect of replacing any binding with the same name that
is not also ``replacing''. Normally a replacement results in an
``override'' warning message, @code{#:replace} avoids that.
This can be used by a module extending a core function in an upwardly
compatible way, like SRFI-39 @code{current-input-port}
(@pxref{SRFI-39}).
This is useful for modules that export bindings that have the same
name as core bindings. @code{#:replace}, in a sense, lets Guile know
that the module @emph{purposefully} replaces a core binding. It is
important to note, however, that this binding replacement is confined
to the name space of the module user. In other words, the value of the
core binding in question remains unchanged for other modules.
Or it can be used by a module which is intentionally producing a new
special kind of environment and should override any core or other
bindings already in scope. For example perhaps a logic processing
environment where @code{<=} is an inference instead of a comparison.
For instance, SRFI-39 exports a binding named
@code{current-input-port} (@pxref{SRFI-39}) that is a function which
is upwardly compatible with the core @code{current-input-port}
function. Therefore, SRFI-39 exports its version with
@code{#:replace}.
@code{#:duplicates} below provides fine-grain control about duplicate
binding handling on the module-user side.
SRFI-19, on the other hand, exports its own version of
@code{current-time} (@pxref{SRFI-19 Time}) which is not compatible
with the core @code{current-time} function (@pxref{Time}). Therefore,
SRFI-19 does not use @code{#:replace}.
The @code{#:replace} option can also be used by a module which is
intentionally producing a new special kind of environment and should
override any core or other bindings already in scope. For example
perhaps a logic processing environment where @code{<=} is an inference
instead of a comparison.
The @code{#:duplicates} (see below) provides fine-grain control about
duplicate binding handling on the module-user side.
@item #:duplicates @var{list}
@cindex duplicate binding handlers