Use domain_error for DIV/0

src/biginteger.cpp

@@ -21,7 +21,7 @@ namespace detail {
   data_type add(data_type rhs, data_type const & lhs);
   data_type subtract_nounderflow(data_type rhs, data_type const & lhs);
   data_type multiply(data_type const & rhs, data_type const & lhs);
-  data_type divide(data_type remainder, data_type const & divisor);
+  std::pair<data_type, data_type> divide(data_type remainder, data_type const & divisor);
 }
 
 static void swap(biginteger & rhs, biginteger && lhs) {
@@ -144,7 +144,7 @@ biginteger math::operator*(biginteger const & rhs, biginteger const & lhs) {
 }
 
 biginteger math::operator/(biginteger const & rhs, biginteger const & lhs) {
-  if (lhs == biginteger::ZERO) { throw 0; }
+  if (lhs == biginteger::ZERO) { throw std::domain_error("cannot divide by 0"); }
   else if (rhs == biginteger::ZERO) { return biginteger::ZERO; }
   else if (detail::compare(lhs.data, {1}) == 0) {
     return {rhs.is_negative != lhs.is_negative, biginteger::data_type{rhs.data}};
@@ -269,7 +269,7 @@ namespace detail {
   data_type divide(data_type remainder, data_type const & divisor) {
     data_type accum{0};
     auto const dig = digits(divisor);
-    while (detail::compare(remainder, divisor) >= 0) {
+    do {
       auto const diff = digits(remainder) - dig - 1;
       auto const shift = diff / biginteger::SEG_DIGITS;
       auto const ipow = diff - (shift * biginteger::SEG_DIGITS);
@@ -279,7 +279,7 @@ namespace detail {
         subtract_from(remainder, value);
         add_into(accum, step);
       } while (detail::compare(remainder, value) >= 0);
-    }
+    } while (detail::compare(remainder, divisor) >= 0);
     return accum;
   }
 }
@@ -307,9 +307,7 @@ bool math::operator>=(biginteger const & rhs, biginteger const & lhs) {
 }
 
 bool math::operator> (biginteger const & rhs, biginteger const & lhs) {
-  if (rhs.is_negative != lhs.is_negative) { return lhs.is_negative; }
-  else if (rhs.is_negative) { return detail::compare(rhs.data, lhs.data) < 0; }
-  else { return detail::compare(rhs.data, lhs.data) > 0; }
+  return lhs < rhs;
 }
 
 biginteger const biginteger::ZERO{0}, biginteger::ONE{1}, biginteger::NEGATIVE_ONE{-1};

test/biginteger.t.h

@@ -99,7 +99,7 @@ public:
   void testDivideByZeroThrows() {
     auto &ZERO =  math::biginteger::ZERO;
     math::biginteger bi{1000};
-    TS_ASSERT_THROWS(bi/ZERO, int);
+    TS_ASSERT_THROWS(bi/ZERO, std::domain_error);
   }
   
   void testDivideByOneReturnsValue() {