* eval.c (eval_init): Register have function, synonym of true.

* txr.1: Document have.

3 files changed, 29 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index a103ae57..60d759f5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-20  Kaz Kylheku  <kaz@kylheku.com>
+
+	* eval.c (eval_init): Register have function, synonym of true.
+
+	* txr.1: Document have.
+
 2015-06-19  Kaz Kylheku  <kaz@kylheku.com>
 
 	* txr.1: Documented ifa.
diff --git a/eval.c b/eval.c
index 41b33865..7d1ef1ae 100644
--- a/eval.c
+++ b/eval.c
@@ -3865,6 +3865,8 @@ static val merge_wrap(val seq1, val seq2, val lessfun, val keyfun)
 
 void eval_init(void)
 {
+  val not_null_f = func_n1(not_null);
+
   protect(&top_vb, &top_fb, &top_mb, &top_smb, &special, &builtin, &dyn_env,
           &op_table, &last_form_evaled, &last_form_expanded,
           &call_f, convert(val *, 0));
@@ -4084,7 +4086,8 @@ void eval_init(void)
   reg_fun(intern(lit("atom"), user_package), func_n1(atom));
   reg_fun(intern(lit("null"), user_package), null_f);
   reg_fun(intern(lit("false"), user_package), null_f);
-  reg_fun(intern(lit("true"), user_package), func_n1(not_null));
+  reg_fun(intern(lit("true"), user_package), not_null_f);
+  reg_fun(intern(lit("have"), user_package), not_null_f);
   reg_fun(not_s, null_f);
   reg_fun(intern(lit("consp"), user_package), func_n1(consp));
   reg_fun(intern(lit("lconsp"), user_package), func_n1(lconsp));
diff --git a/txr.1 b/txr.1
index c41867b3..9fa7328f 100644
--- a/txr.1
+++ b/txr.1
@@ -12993,9 +12993,10 @@ otherwise.
       (format t "list ~s does not contain the symbol a\en")))
 .cble
 
-.coNP Function @ true
+.coNP Functions @ true and @ have
 .synb
 .mets (true << value )
+.mets (have << value )
 .syne
 .desc
 
@@ -13006,7 +13007,10 @@ function is the complement of the
 .code not
 and
 .code false
-functions.
+functions. The
+.code have
+function is a synonym for
+.codn true .
 
 It return
 .code t
@@ -13026,6 +13030,19 @@ For instance
 .code (if x ...)
 should be favored over
 .codn (if (true x) ...) .
+However, the latter is useful with the
+.code ifa
+macro because
+.meti (ifa (true << expr ) ...)
+binds the
+.code it
+variable to the value of
+.metn expr ,
+no matter what kind of form
+.meta expr
+is, which is not true in the
+.meti (ifa < expr ...)
+form.
 
 .TP* Example:
 .cblk