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2.6.11  The integer Euclidean remainder : irem remain smod mods mod %

irem (or remain) returns the integer remainder r from the Euclidean division of two integers a and b given as arguments (a=b*q+r avec 0≤ r< b).
For Gaussian integers, we choose q so that b*q is as near by a as possible and it can be proved that r may be choosen so that |r|2 ≤ |b|2/2.
Input :

irem(148,5)

Output :

3

irem works with long integers or with Gaussian integers.
Example :

irem(factorial(148),factorial(45)+2 )

Output :

111615339728229933018338917803008301992120942047239639312

Another example

irem(25+12*i,5+7*i)

Output :

-4+i

Here ab*q=−4+i and |−4+i|2=17<|5+7*i|2/2=74/2=37

smod or mods is a prefixed function and has two integers a and b as arguments.
smod or mods returns the symetric remainder s of the Euclidean division of the arguments a and b (a=b*q+s with −b/2<sb/2).
Input :

smod(148,5)

Output :

-2

mod (or %) is an infixed function and has two integers a and b as arguments.
mod (or %) returns r% b of Z/bZ where r is the remainder of the Euclidean division of the arguments a and b.
Input :

148 mod 5

or

148 % 5

Output :

3 % 5

Note that the answer 3 % 5 is not an integer (3) but an element of Z/5Z (see 2.31 to have the possible operations in Z/5Z).


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