[PATCH 19/25] Document define-foreign-bitmask macro

[KAction]

From: Dmitry Bogatov <address@hidden>

---
 doc/ref/api-foreign.texi | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/doc/ref/api-foreign.texi b/doc/ref/api-foreign.texi
index 605dbed..6b0e34c 100644
--- a/doc/ref/api-foreign.texi
+++ b/doc/ref/api-foreign.texi
@@ -1124,6 +1124,22 @@ Here are some examples of @code{define-foreign-function} 
usage:
 @end example
 @end deffn
 
address@hidden {Scheme Macro} define-foreign-bitmask name ((symbol value) ...)
+
+Define @code{name} to foreign-type record, that converts back and forth
+between C integer value and Scheme list of symbols. For example,
address@hidden
+(define-foreign-bitmask both: ((this #b01) (that #b10) (both #b11)))
+;; 0 = #b00 <-> '()
+;; 1 = #b01 <-> '(this)
+;; 2 = #b10 <-> '(that)
+;; 3 = #b11 <-> '(this that both)
address@hidden example
+
+As demonstrated by example, values can be arbitrary, but in most common
+each value have only one bit set.
address@hidden deffn
+
 @c Local Variables:
 @c TeX-master: "guile.texi"
 @c End:
-- 
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