round a number to the nearest ten thousandth in swift

To round a number to the nearest ten thousandth in Swift, you can use the round function from the Foundation framework. Here's an example:

main.swift
let x: Double = 1.23456789
let y = round(x * 10000) / 10000 // y = 1.2346
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In this example, we first multiply the number by 10000 to shift the decimal point to the right by four places. Then we call the round function to round the number to the nearest integer. Finally, we divide the result by 10000 to shift the decimal point back to its original position.

Note that you can also use the roundf function if you're working with Float instead of Double.