lib: revise wording of integer range errors.

* arith.c (c_unum): Fix misleading error message, and instead
specify the range that was violated.

* lib.c (c_num): Similar change: don't refer to a 'cnum range'
which means nothing to the user.

2 files changed, 10 insertions, 8 deletions

diff --git a/arith.c b/arith.c
index bd66bfbc..8bc459ca 100644
--- a/arith.c
+++ b/arith.c
@@ -213,7 +213,8 @@ ucnum c_unum(val num)
     }
     /* fallthrough */
   range:
-    uw_throwf(error_s, lit("~s given, non-negative expected"), num, nao);
+    uw_throwf(error_s, lit("~s is out of allowed range [0, ~a]"),
+              num, unum(UINT_PTR_MAX), nao);
   default:
     type_mismatch(lit("~s is not an integer"), num, nao);
   }
diff --git a/lib.c b/lib.c
index 925bf638..26806b41 100644
--- a/lib.c
+++ b/lib.c
@@ -3099,20 +3099,21 @@ val num(cnum n)
   return bignum(n);
 }
 
-cnum c_num(val num)
+cnum c_num(val n)
 {
-  switch (type(num)) {
+  switch (type(n)) {
   case CHR: case NUM:
-    return coerce(cnum, num) >> TAG_SHIFT;
+    return coerce(cnum, n) >> TAG_SHIFT;
   case BGNUM:
-    if (in_int_ptr_range(num)) {
+    if (in_int_ptr_range(n)) {
       int_ptr_t out;
-      mp_get_intptr(mp(num), &out);
+      mp_get_intptr(mp(n), &out);
       return out;
     }
-    uw_throwf(error_s, lit("~s is out of cnum range"), num, nao);
+    uw_throwf(error_s, lit("~s is out of allowed range [~s, ~s]"),
+              n, num(INT_PTR_MIN), num(INT_PTR_MAX), nao);
   default:
-    type_mismatch(lit("~s is not an integer"), num, nao);
+    type_mismatch(lit("~s is not an integer"), n, nao);
   }
 }