How to find max value for Double and Float in Swift

As of Swift 3+, you should use:

CGFloat.greatestFiniteMagnitudeDouble.greatestFiniteMagnitudeFloat.greatestFiniteMagnitude

While there’s no Double.max, it is defined in the C float.h header, which you can access in Swift via import Darwin.

import Darwinlet fmax = FLT_MAXlet dmax = DBL_MAX

These are roughly 3.4 * 10^38 and 1.79 * 10^308 respectively.

But bear in mind it’s not so simple with floating point numbers (it’s never simple with floating point numbers). When holding numbers this large, you lose precision in a similar way to losing precision with very small numbers, so:

let d = DBL_MAXlet e = d - 1.0let diff = d - ediff == 0.0  // truelet maxPlusOne = DBL_MAX + 1maxPlusOne == d  // truelet inf = DBL_MAX * 2// perhaps infinity is the “maximum” inf == Double.infinity  // true

So before you get into some calculations that might possibly brush up against these limits, you should probably read up on floating point. Here and here are probably a good start.

AV's answer is fine, but I find those macros hard to remember and a bit non-obvious, so eventually I made Double.MIN and friends work:

extension Double {    static var MIN     = -DBL_MAX    static var MAX_NEG = -DBL_MIN    static var MIN_POS =  DBL_MIN    static var MAX     =  DBL_MAX}

Don't use lowercase min and max -- those symbols are used in Swift 3.