expand-hook: process DWIM brackets forms.

It turns out we need this for infix.

* eval.c (do_expand): Call the expand hook for
forms headed by the dwim operator, passing that
operator symbol as the type indicator.

* txr.1: Document this and also that the
expand hook doesn't receive symbol macros.

2 files changed, 27 insertions, 12 deletions

diff --git a/eval.c b/eval.c
index 9c35d6c5..24e4dd92 100644
--- a/eval.c
+++ b/eval.c
@@ -5362,12 +5362,22 @@ again:
     } else if (sym == symacrolet_s) {
       return expand_symacrolet(form, menv);
     } else if (sym == dwim_s) {
-      val args = rest(form);
-      val args_ex = expand_forms_lisp1(dot_to_apply(args, t), menv);
+      val eh = expand_hook;
+      if (eh) {
+        val eform = funcall3(eh, form, menv, dwim_s);
+        if (eform != form) {
+          form = rlcp_tree(eform, form);
+          goto again;
+        }
+      }
+      {
+        val args = rest(form);
+        val args_ex = expand_forms_lisp1(dot_to_apply(args, t), menv);
 
-      if (args == args_ex)
-        return form;
-      return rlcp(cons(sym, args_ex), form);
+        if (args == args_ex)
+          return form;
+        return rlcp(cons(sym, args_ex), form);
+      }
     } else if (sym == switch_s) {
       return expand_switch(form, menv);
     } else if (!macro && (macro = lookup_mac(menv, sym))) {
diff --git a/txr.1 b/txr.1
index 388616fd..5db0bbef 100644
--- a/txr.1
+++ b/txr.1
@@ -44021,11 +44021,13 @@ a function which takes three arguments:
 .mono
 .meti (lambda >> ( form < env << type-keyword ) ...)
 .onom
-Whenever the macro expander encounters the invocation of a symbol macro,
-macro, function, or invalid form, it calls the function stored in
+Whenever the macro expander encounters the invocation of a macro,
+macro, function, DWIM brackets form, or an invalid form, it calls the function
+stored in
 .code *expand-hook*
 if that variable isn't
 .codn nil .
+The hook is not invoked for symbol macro forms.
 
 If the function returns an expression other than
 .metn form ,
@@ -44054,9 +44056,10 @@ and others in that category.
 
 The
 .meta type-keyword
-argument takes on one of three values:
+argument takes on one of four values:
 .codn :fun ,
-.code :macro
+.codn :macro ,
+.code dwim
 or
 .codn nil .
 If the value is
@@ -44070,8 +44073,10 @@ If the value is
 .codn :macro ,
 then
 .meta form
-is a macro invocation: if it is a symbol, then it is a symbol macro form,
-otherwise an ordinary macro form.
+is a macro invocation. If the value is
+.codn dwim ,
+it is a bracket form: a compound form headed by the same symbol
+.codn dwim .
 If
 .meta type-keyword
 is
@@ -54018,7 +54023,7 @@ atoms, considering them to be the tokens of infix syntax.
 The
 .code ifx
 macro establishes an expansion hook as if by binding the variable
-.codn *expander-hook* .
+.codn *expand-hook* .
 Whenever the expansion hook transforms a form, the expression's
 constituent forms are then recursively visited, and subject to
 automatic infix expansion.