* arith.c (divi): Support one-argument form.

Use "/" name in error reporting, not "divi".

* eval.c (eval_init): Change registration of / so only
one argument is required out of two.

* txr.1: Document one-argument division.

1 files changed, 12 insertions, 5 deletions

diff --git a/arith.c b/arith.c
index 14d3d0e2..7051ddb8 100644
--- a/arith.c
+++ b/arith.c
@@ -946,13 +946,20 @@ static val to_float(val func, val num)
 
 val divi(val anum, val bnum)
 {
-  double a = c_flo(to_float(lit("divi"), anum));
-  double b = c_flo(to_float(lit("divi"), bnum));
+  if (missingp(bnum)) {
+    double b = c_flo(to_float(lit("/"), anum));
+    if (b == 0.0)
+      uw_throw(numeric_error_s, lit("/: division by zero"));
+    return flo(1.0 / b);
+  } else {
+    double a = c_flo(to_float(lit("/"), anum));
+    double b = c_flo(to_float(lit("/"), bnum));
 
-  if (b == 0.0)
-    uw_throw(numeric_error_s, lit("divi: division by zero"));
+    if (b == 0.0)
+      uw_throw(numeric_error_s, lit("/: division by zero"));
 
-  return flo(a / b);
+    return flo(a / b);
+  }
 }
 
 val zerop(val num)