Editing Hash function (section)

=== Variable range ===
In many applications, the range of hash values may be different for each run of the program or may change along the same run (for instance, when a hash table needs to be expanded). In those situations, one needs a hash function which takes two parameters—the input data {{math|''z''}}, and the number {{math|''n''}} of allowed hash values.

A common solution is to compute a fixed hash function with a very large range (say, {{math|0}} to {{math|2<sup>32</sup>&nbsp;−&nbsp;1}}), divide the result by {{math|''n''}}, and use the division's [[modulo operation|remainder]]. If {{math|''n''}} is itself a power of {{math|2}}, this can be done by [[Mask (computing)|bit masking]] and [[bit shifting]]. When this approach is used, the hash function must be chosen so that the result has fairly uniform distribution between {{math|0}} and {{math|''n''&nbsp;−&nbsp;1}}, for any value of {{math|''n''}} that may occur in the application. Depending on the function, the remainder may be uniform only for certain values of {{math|''n''}}, e.g. [[odd number|odd]] or [[prime number]]s.