diff --git a/doc/ref/api-modules.texi b/doc/ref/api-modules.texi index f6f298522..91e70f39f 100644 --- a/doc/ref/api-modules.texi +++ b/doc/ref/api-modules.texi @@ -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