!standard 4.5.5(8) 11-06-19 AI05-0260-1/01 !class binding interpretation 11-06-19 !status work item 11-06-16 !status received 11-05-17 !priority Low !difficulty Easy !qualifier Error !subject Pedantic question on the wording of the definition of modulo !summary Zero doesn't have a sign, so we need to except it from the wording. !question 4.5.5(8) says: The signed integer modulus operation is defined such that the result of A mod B has the sign of B and an absolute value less than the absolute value of B; in addition, for some signed integer value N, the result satisfies the relation: A = B*N + (A mod B) If A := 0 and B < 0 then the only solution to the relation that has abs(A mod B) < abs(B) is A mod B = 0. But 0 does not have the "sign of B" (it is not negative). Should this be fixed? (Yes.) !wording Modify the start of 4.5.5(8): The signed integer modulus operation is defined such that the result of A mod B {is either zero, or} has the sign of B and an absolute value less than the absolute value of B; in addition, ... !discussion !ACATS Test None needed. !ASIS No change needed. !appendix !topic Pedantic question on the wording of the definition of modulo !reference Ada 2005 RM !from Martin Brain 11-05-17 !keywords multiplicative operators, modulo, pendantry !discussion In the Ada 2005 LRM (ISO/IEC 8652:2007 Ed 3), Section 4.5.5 defines the modulo operator as: The signed integer modulus operation is defined such that the result of A mod B has the sign of B and an absolute value less than the absolute value of B; in addition, for some signed integer value N, the result satisfies the relation: A = B*N + (A mod B) If A := 0 and B < 0 then the only solution to the relation that has abs(A mod B) < abs(B) is A mod B = 0, which I believe to be the intended and expected result. However the sign of zero is not the same as the sign of a negative number, giving a contradiction. Although this is a point of pedantry, it would be nice if the wording of the definition was changed. **************************************************************** From: Adam Beneschan Sent: Tuesday, May 17, 2011 2:42 PM I think I'd change it to The signed integer modulus operation is defined such that the result of A mod B is either zero, or has the sign of B and an absolute value less than the absolute value of B; in addition, ... ****************************************************************