Fix misleading documentation under if/iffi.

* txr.1: Examples under iff and iffi had two issues:
the false predicate function was used in a role which calls
for a function that unconditionally returns nil.
The correct function is nilf. Square brackets must
be used, otherwise nilf and identity are unbound
variables. Also the equivalence for [iff a] now
indicates that it's equiavlent to a, showing that
it's not useful to default both arguments.

1 files changed, 4 insertions, 4 deletions

diff --git a/txr.1 b/txr.1
index 789c06b6..b7bfd01c 100644
--- a/txr.1
+++ b/txr.1
@@ -28556,17 +28556,17 @@ and
 
   (iffi a b)              <--> (iff a b identity)
 
-  (iffi a b false)        <--> (iff a b)
+  [iffi a b nilf]         <--> [iff a b]
 
-  (iffi a identity false) <--> (iff a)
+  [iffi a identity nilf]  <--> [iff a]
 .cble
 
-The following equivalence illustrates
+The following equivalences illustrate
 .code iff
 with both optional arguments omitted:
 
 .cblk
-  (iff a)  <--->  (iff a identity false)
+  [iff a]  <--->  [iff a identity nilf]  <--->  a
 .cble
 
 .coNP Functions @ tf and @ nilf