How Can We Compactly Define Powers of 1000 as Constants in Go?

How to Compactly Express Powers of 10 as Constants

In the Go Programming Language, the concept of constants is introduced with iota as a powerful mechanism for generating compact and readable constant values. Exercise 3.13 of the book challenges readers to succinctly define constants representing powers of 1000 (KB, MB, etc.).

While the exercise may appear to require a sophisticated solution involving iota, the authors explicitly state that this approach is not feasible due to the lack of exponentiation in Go. Instead, they encourage readers to explore "as compact as" solutions.

Floating-Point Literals Approach

One compact approach is to utilize floating-point literals with an exponent part. For example, the constant 1e3 represents the value 1000, and each subsequent constant can be obtained by multiplying by 1000 or simply adding 3 to the exponent. This method results in the following one-line declaration (excluding spaces):

const ( KB, MB, GB, TB, PB, EB, ZB, YB = 1e3, 1e6, 1e9, 1e12, 1e15, 1e18, 1e21, 1e24 )

Integer Literals Approach

Alternatively, for untyped integer constants, we can multiply subsequent constants by 1000. However, we can save space by utilizing the previous constant as the multiplier instead. For example, MB can be defined as KB 1000 or simply KB KB.

const (KB, MB, GB, TB, PB, EB, ZB, YB = 1000, KB*KB, MB*KB, GB*KB, TB*GB, PB*KB, EB*KB, ZB*KB)

Introducing an Extra Constant

This solution can be further refined by introducing an extra constant x representing 1000. By using x as the multiplier, we save 3 characters.

const (x, KB, MB, GB, TB, PB, EB, ZB, YB = 1000, x, x*x, MB*x, GB*x, TB*GB, PB*x, EB*x, ZB*x)

Rune Literal Approach

Finally, for maximum compactness, we can assign the value 1000 to a rune constant. In Unicode, the code point 1000 represents the character 'Ϩ,' which is 1 character shorter than 'x.'

const (x, KB, MB, GB, TB, PB, EB, ZB, YB = 'Ϩ', x, x*x, MB*x, GB*x, TB*GB, PB*x, EB*x, ZB*x)

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