Pure Function
In computer programming, a function may be described as pure if both these statements about the function hold:
- The function always evaluates the same result value given the same argument value(s). The function result value cannot depend on any hidden information or state that may change as program execution proceeds or between different executions of the program, nor can it depend on any external input from I/O devices.
- Evaluation of the result does not cause any semantically observable side effect or output, such as mutation of mutable objects or output to I/O devices.
The result value need not depend on all (or any) of the argument values. However, it must depend on nothing other than the argument values. The function may return multiple result values and these conditions must apply to all returned values for the function to be considered pure. If an argument is call by reference it is considered to be a combination of one argument and one return value and so the argument will get overwritten; because of this call by reference will make an expression impure even if the function called is pure.
Read more about Pure Function: Pure Expressions, Impure Functions in Pure Expressions, See Also
Famous quotes containing the words pure and/or function:
“White Pond and Walden are great crystals on the surface of the earth, Lakes of Light.... They are too pure to have a market value; they contain no muck. How much more beautiful than our lives, how much more transparent than our characters are they! We never learned meanness of them.”
—Henry David Thoreau (1817–1862)
“Our father has an even more important function than modeling manhood for us. He is also the authority to let us relax the requirements of the masculine model: if our father accepts us, then that declares us masculine enough to join the company of men. We, in effect, have our diploma in masculinity and can go on to develop other skills.”
—Frank Pittman (20th century)