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Using the XOR swap algorithm to exchange nibbles between variables without the use of temporary storage. In computer programming, the exclusive or swap (sometimes shortened to XOR swap) is an algorithm that uses the exclusive or bitwise operation to swap the values of two variables without using the temporary variable which is normally required.
This method swaps two variables by adding and subtracting their values. This is rarely used in practical applications, mainly because: It can only swap numeric variables; it may not be possible or logical to add or subtract complex data types, like containers. When swapping variables of a fixed size, arithmetic overflow becomes an issue.
Early ALGOL compilers supported a SWITCH data type which contains a list of "designational expressions". A GOTO statement could reference a switch variable and, by providing an index, branch to the desired destination. With experience it was realized that a more formal multi-way construct, with single point of entrance and exit, was needed.
Change of variables is an operation that is related to substitution. However these are different operations, as can be seen when considering differentiation or integration (integration by substitution). A very simple example of a useful variable change can be seen in the problem of finding the roots of the sixth-degree polynomial:
Temporary variables, along with XOR swaps and arithmetic operators, are one of three main ways to exchange the contents of two variables. To swap the contents of variables "a" and "b" one would typically use a temporary variable temp as follows, so as to preserve the data from a as it is being overwritten by b: temp := a a := b b := temp
For a value of 1 it would return "one". For a value of 2 it would return "two". For the values 3, 4 or 5 it would return "range 3–5". For any other value, or a null value, it would return "other". However, in many cases, the #switch function is a multi-line form, with each branch on a different line, as follows:
2. In a medium bowl, stir the flour, pudding mix, cream of tartar, baking soda and salt. With the mixer on low, gradually add the dry ingredients to the butter mixture, beating just until ...
Consider the process of swapping the values of two variables, x and y. Assuming weak typing and not being concerned about name collision, this is represented by the code: temp = x x = y y = temp When the snippet is inserted, the programmer is prompted for the values of the two parameters.