Bugfix: ifa must allow dwim expressions.

* share/txr/stdlib/ifa.tl (ifa): Accept dwim expressions
as the condition. Moreover, treat [f x] as a one-argument
call, even though it is the two-argument form (dwim f x).

* txr.1: Documented.

1 files changed, 6 insertions, 3 deletions

diff --git a/share/txr/stdlib/ifa.tl b/share/txr/stdlib/ifa.tl
index aa406bbd..cefb38eb 100644
--- a/share/txr/stdlib/ifa.tl
+++ b/share/txr/stdlib/ifa.tl
@@ -35,11 +35,12 @@
                  (first test)))
        ^(ifa ,(second test) ,else ,then))
       (t (let* ((sym (first test))
-                (args (rest test))
+                (args (if (eq 'dwim sym) (cddr test) (cdr test)))
                 (n-candidate-args [count-if candidate-p args])
                 (pos-candidate (or [pos-if candidate-p args] 0)))
            (unless (or (lexical-fun-p e sym)
                        (and (or (functionp (symbol-function sym))
+                                (eq sym 'dwim)
                                 (null (symbol-function sym)))))
              (throwf 'eval-error "ifa: test expression must be \
                                  \ a simple function call"))
@@ -55,12 +56,14 @@
                  ^(let (,*(zip btemps before-it))
                     (placelet ((it ,it-form))
                       (let (,*(zip atemps after-it))
-                        (if (,sym ,*btemps it ,*atemps)
+                        (if (,sym ,*(if (eq 'dwim sym) ^(,(second test)))
+                                  ,*btemps it ,*atemps)
                           ,then ,else))))))
              (let* ((temps (mapcar (ret (gensym)) args))
                     (it-temp [temps pos-candidate]))
                ^(let* (,*(zip temps args) (it ,it-temp))
-                  (if (,sym ,*temps) ,then ,else)))))))))
+                  (if (,sym ,*(if (eq 'dwim sym) ^(,(second test)))
+                            ,*temps) ,then ,else)))))))))
 
 (defmacro conda (. pairs)
   (tree-case pairs