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authorKaz Kylheku <kaz@kylheku.com>2016-12-20 11:04:30 -0800
committerKaz Kylheku <kaz@kylheku.com>2016-12-20 11:04:30 -0800
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doc: document place expander hashes.
* txr.1: Document *place-update-expander*, *place-clobber-expander* and *place-delete-expander*.
-rw-r--r--txr.117
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diff --git a/txr.1 b/txr.1
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@@ -30400,6 +30400,23 @@ treat the situation in a satisfactory way using a
definition, which effectively then supplies inline code whenever a certain form
is used as a place, and that code itself is treated as a place.
+.coNP Special variables @, *place-update-expander* @ *place-clobber-expander* and @ *place-delete-expander*
+.desc
+These variables hold hash tables, by means of which update expanders,
+clobber expanders and delete expanders are registered, as associations
+between symbols and functions.
+
+If
+.code "[*place-update-expander* 'sym]"
+yields a function, then symbol
+.code sym
+is the basis for a syntactic place. If the expression yields
+.codn nil ,
+then forms beginning with
+.code sym
+are not syntactic places. (The situation of a clobber accessor or delete
+accessor being defined without an update expander is improper).
+
.SS* Quasiquote Operator Syntax
.coNP Macro @ qquote
.synb