(octave.info)Integer Arithmetic

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4.4.1 Integer Arithmetic
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While many numerical computations can’t be carried out in integers,
Octave does support basic operations like addition and multiplication on
integers.  The operators ‘+’, ‘-’, ‘.*’, and ‘./’ work on integers of
the same type.  So, it is possible to add two 32 bit integers, but not
to add a 32 bit integer and a 16 bit integer.

   When doing integer arithmetic one should consider the possibility of
underflow and overflow.  This happens when the result of the computation
can’t be represented using the chosen integer type.  As an example it is
not possible to represent the result of 10 - 20 when using unsigned
integers.  Octave makes sure that the result of integer computations is
the integer that is closest to the true result.  So, the result of 10 -
20 when using unsigned integers is zero.

   When doing integer division Octave will round the result to the
nearest integer.  This is different from most programming languages,
where the result is often floored to the nearest integer.  So, the
result of ‘int32 (5) ./ int32 (8)’ is ‘1’.

 -- : idivide (X, Y, OP)
     Integer division with different rounding rules.

     The standard behavior of integer division such as ‘A ./ B’ is to
     round the result to the nearest integer.  This is not always the
     desired behavior and ‘idivide’ permits integer element-by-element
     division to be performed with different treatment for the
     fractional part of the division as determined by the OP flag.  OP
     is a string with one of the values:

     "fix"
          Calculate ‘A ./ B’ with the fractional part rounded towards
          zero.

     "round"
          Calculate ‘A ./ B’ with the fractional part rounded towards
          the nearest integer.

     "floor"
          Calculate ‘A ./ B’ with the fractional part rounded towards
          negative infinity.

     "ceil"
          Calculate ‘A ./ B’ with the fractional part rounded towards
          positive infinity.

     If OP is not given it defaults to "fix".  An example demonstrating
     these rounding rules is

          idivide (int8 ([-3, 3]), int8 (4), "fix")
            ⇒ int8 ([0, 0])
          idivide (int8 ([-3, 3]), int8 (4), "round")
            ⇒ int8 ([-1, 1])
          idivide (int8 ([-3, 3]), int8 (4), "floor")
            ⇒ int8 ([-1, 0])
          idivide (int8 ([-3, 3]), int8 (4), "ceil")
            ⇒ int8 ([0, 1])

     See also: Note: ldivide, Note: rdivide.