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Document quote-syntax

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* NEWS: Update.
* doc/ref/api-macros.texi (Syntax Case): Update.
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Andy Wingo 2021-03-09 20:49:46 +01:00
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doc/ref/api-macros.texi
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@ -799,6 +799,24 @@ Note that @code{with-ellipsis} does not affect the ellipsis identifier
of the generated code, unless @code{with-ellipsis} is included around
the generated code.
@subsubsection Syntax objects can be data too
Generally speaking, you want the macro expander to pick apart all syntax
objects in a source term. The source and scope annotations attached to
the syntax object are of interest to how the macro expander computes the
result, but no syntax object itself should appear in the expanded
term---usually. Sometimes, though, a macro will want a syntax object to
appear in the expanded output. Normally you would just use @code{quote}
to introduce the syntax object as a value, but the expander strips
syntax objects from subexpression of @code{quote}. For this rare use
case, Guile has @code{quote-syntax}, which does not strip its
subexpression.
@deffn {Syntax} quote-syntax form
Expand to the syntax object @code{form}, as a constant literal. Like
@code{quote}, but without calling @code{syntax->datum}.
@end deffn
@node Syntax Transformer Helpers
@subsection Syntax Transformer Helpers