Using the exponentiation operator

D has a built-in exponentiation operator: the ^^ operator.

How to do it…

In order to use the exponentiation operator, we need to execute the following steps:

1. Write an expression with the ^^ operator.

2. Make one or both arguments floating point if you want a floating point result.

The code is as follows:

int a = 2^^3; // a == 8
float b = 2.0 ^^ 3.0; // b == 8.0
auto c = 2 * 2 ^^ 3; // c == 16

How it works…

The exponentiation operator is first subject to constant folding and is then rewritten into a call to the std.math.pow library function to perform the operation. The result follows the regular arithmetic type rules of the D language, so the int arguments yield an int result and the float arguments yield a float result.

The operator also follows the usual arithmetic order of operations, so it has higher precedence than multiplication, as seen in the third example line.

The choice of ^^ for the operator was driven by the desire: to look like ASCII math without being confusing in the context of the D programming language. The two other major competitors, ^ and **, were rejected because they conflict with existing operations inherited by C: ^ is the bitwise XOR operator in both C and D, while ** is currently parsed as multiplication of a dereferenced pointer. While the lexer could be changed to make it into a new operator, this could potentially lead to silent breakages when porting C code to D, which D tries to avoid. (D doesn't mind breaking C code, but it prefers it to be a compile error whenever possible instead of code that compiles the same then acts differently.)

Thus, ^^ was chosen, and it is visually similar to how exponentiation is often written in ASCII text (2^3 for example), without being in conflict with any existing C or D code.

Note

Why isn't ^^ used for Boolean XOR in the same way that || is Boolean OR and && is Boolean AND? It is because Boolean XOR already has an operator: !=. If you write out the truth tables for is-not-equal, you'll find they are an exact match for a hypothetical Boolean XOR!