Typescript Numeric Literal Types X-Y (Subtraction)

Acid Coder
Jun 30, 2022

We have seen how can we add two numeric literals type

now can we apply similar tricks for subtraction?

yes we can, this is how we do it:

type CreateArrayWithLengthX<
LENGTH extends number,
ACC extends unknown[] = [],
> = ACC['length'] extends LENGTH
? ACC
: CreateArrayWithLengthX<LENGTH, [...ACC,1]>

type Subtraction<LARGER extends number, SMALLER extends number, GAP extends number[] = []> =
[...GAP,...CreateArrayWithLengthX<SMALLER>]['length'] extends [...CreateArrayWithLengthX<LARGER>]['length']
? GAP['length']
: Subtraction<LARGER, SMALLER, [1,...GAP]>

type result = Subtraction<849, 654> // 195

playground

limitation: the number cannot exceed 999 because the max depth of TS recursion is only 1000, only work with positive integer

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Acid Coder

Typescript Zombie. Youtube Pikachu On Acid. (Unrelated to programming but by watching it you become a good developer overnight)