Editing Relational operator (section)

==Ordering==
''Greater than'' and ''less than'' comparison of non-numeric data is performed according to a sort convention (such as, for text strings, [[lexicographical order]]) which may be built into the programming language and/or configurable by a programmer.

When it is desired to associate a numeric value with the result of a comparison between two data items, say ''a'' and ''b'', the usual convention is to assign &minus;1 if a < b, 0 if a = b and 1 if a > b. For example, the C function <code>[[strcmp]]</code> performs a [[three-way comparison]] and returns &minus;1, 0, or 1 according to this convention, and [[qsort]] expects the comparison function to return values according to this convention. In [[sorting algorithm]]s, the efficiency of comparison code is critical since it is one of the major factors contributing to sorting performance.

Comparison of programmer-defined [[data type]]s (data types for which the programming language has no in-built understanding) may be carried out by custom-written or library functions (such as <code>strcmp</code> mentioned above), or, in some languages, by ''[[Operator overloading|overloading]]'' a comparison operator – that is, assigning a programmer-defined meaning that depends on the data types being compared. Another alternative is using some convention such as member-wise comparison.