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[poincare] Fix integer subtraction (overflow in carry)

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This commit is contained in:
Émilie Feral
2017-12-08 10:11:55 +01:00
committed by Ecco
parent 9b72bc86fa
commit 8c37e8a6d0
2 changed files with 38 additions and 1 deletions
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6
poincare/src/integer.cpp
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@@ -381,7 +381,11 @@ Integer Integer::usum(const Integer & a, const Integer & b, bool subtract, bool
native_uint_t bDigit = (i >= b.m_numberOfDigits ? 0 : b.digit(i));
native_uint_t result = (subtract ? aDigit - bDigit - carry : aDigit + bDigit + carry);
digits[i] = result;
carry = (subtract ? (aDigit<result+carry) : ((aDigit>result)||(bDigit>result))); // There's been an underflow or overflow
if (subtract) {
carry = (aDigit < result) || (carry && aDigit == result); // There's been an underflow
} else {
carry = (aDigit > result) || (bDigit > result); // There's been an overflow
}
}
while (digits[size-1] == 0 && size>1) {
size--;

33
poincare/test/integer.cpp
View File

@@ -34,6 +34,20 @@ QUIZ_CASE(poincare_integer_addition) {
assert(Integer::Addition(Integer("-123456789123456789"), Integer("123456789123456789")).isEqualTo(Integer("0")));
assert(Integer::Addition(Integer("234"), Integer(-234)).isEqualTo(Integer(0)));
assert(Integer::Addition(Integer("18446744073709551616"), Integer("18446744073709551368")).isEqualTo(Integer("36893488147419102984")));
//2^64+2^64
assert(Integer::Addition(Integer("18446744073709551616"), Integer("18446744073709551616")).isEqualTo(Integer("36893488147419103232")));
//2^64+2^32
assert(Integer::Addition(Integer("18446744073709551616"), Integer("4294967296")).isEqualTo(Integer("18446744078004518912")));
//2^64+1
assert(Integer::Addition(Integer("18446744073709551616"), Integer("1")).isEqualTo(Integer("18446744073709551617")));
//2^32+2^32
assert(Integer::Addition(Integer("4294967296"), Integer("4294967296")).isEqualTo(Integer("8589934592")));
//2^32+1
assert(Integer::Addition(Integer("4294967296"), Integer("1")).isEqualTo(Integer("4294967297")));
//2^16+1
assert(Integer::Addition(Integer("65537"), Integer("1")).isEqualTo(Integer("65538")));
//2^16+2^16
assert(Integer::Addition(Integer("65537"), Integer("65537")).isEqualTo(Integer("131074")));
}
QUIZ_CASE(poincare_integer_subtraction) {
@@ -45,6 +59,25 @@ QUIZ_CASE(poincare_integer_subtraction) {
assert(Integer::Subtraction(Integer("-123456789123456789"), Integer("-123456789123456789")).isEqualTo(Integer(0)));
assert(Integer::Subtraction(Integer("123456789123456789"), Integer("123456789123456789")).isEqualTo(Integer(0)));
assert(Integer::Subtraction(Integer("18446744073709551616"), Integer("18446744073709551368")).isEqualTo(Integer(248)));
//2^64-2^64
assert(Integer::Subtraction(Integer("18446744073709551616"), Integer("18446744073709551616")).isEqualTo(Integer("0")));
//2^64-2^32
assert(Integer::Subtraction(Integer("18446744073709551616"), Integer("4294967296")).isEqualTo(Integer("18446744069414584320")));
//2^32-2^64
assert(Integer::Subtraction(Integer("4294967296"), Integer("18446744073709551616")).isEqualTo(Integer("-18446744069414584320")));
//2^64-1
assert(Integer::Subtraction(Integer("18446744073709551616"), Integer("1")).isEqualTo(Integer("18446744073709551615")));
//1-2^64
assert(Integer::Subtraction(Integer("1"), Integer("18446744073709551616")).isEqualTo(Integer("-18446744073709551615")));
//2^32-2^32
assert(Integer::Subtraction(Integer("4294967296"), Integer("4294967296")).isEqualTo(Integer("0")));
//2^32-1
assert(Integer::Subtraction(Integer("4294967296"), Integer("1")).isEqualTo(Integer("4294967295")));
//2^16-1
assert(Integer::Subtraction(Integer("65537"), Integer("1")).isEqualTo(Integer("65536")));
//2^16-2^16
assert(Integer::Subtraction(Integer("65537"), Integer("65537")).isEqualTo(Integer("0")));
}
QUIZ_CASE(poincare_integer_multiplication) {