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According to Apple's documentation, Swift doesn't support preprocessor directives. In C/Objective-c the "INFINITY" definition is very useful for some checks. So, How do I get a number that never is less that another?

Daniel
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  • You could try dividing the float one by the float zero. – Pascal Cuoq Jun 04 '14 at 03:25
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    @Pascal: That probably gets you the float NaN. Or a crash. – rickster Jun 04 '14 at 04:06
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    @rickster I believe that the folk at Apple are a little more familiar with IEEE 754 than that. – Pascal Cuoq Jun 04 '14 at 05:42
  • @rickster, dividing by zero triggers an exception only with integer division. Edge case floating-point divisions are well-defined and do not cause CPU exceptions. – zneak Jun 04 '14 at 06:18
  • Swift does not support preprocessor directives, but thanks to the module implementation, Swift doesn't have to parse header files to have access to all what's inside. In fact, Swift *does* [translate simple macro values](https://developer.apple.com/library/prerelease/ios/documentation/swift/conceptual/buildingcocoaapps/InteractingWithCAPIs.html#//apple_ref/doc/uid/TP40014216-CH8-XID_22) into global variables. I don't have access to the compiler, but have you tried simply using `INFINITY`? – zneak Jun 04 '14 at 06:29
  • @zneak I tried, but Xcode throw a error message "Use of unresolved identifier". Anyway, I am checking the "Simple Macros", that's very helpful, thanks. – Daniel Jun 04 '14 at 12:48
  • Using INFINITY directly results in an unresolved symbol error. I am using this homegrown formulae for dealing with 64-bit Doubles: unsafeBitCast(0x7ff << 52, Double.self) – John Difool May 26 '15 at 05:51

4 Answers4

41

There is already buildin infinity and also a check function. And you could also directly compare them with <.

var infinity = Double.infinity
var isInfinite = infinity.isInfinite
var someDouble = 234432.0
if someDouble < infinity {
    println("Less than")
} else {
    println("Small than")
}
// And the answer is Less than.
sunkehappy
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13

For integer values, you should use Int.max. 

var highestNumber = Int.max

//if you need negative infinity
var lowestNumber = Int.min

Using NSIntegerMax instead of Int.max or -1 * NSIntegerMax instead of Int.min is equivalent, but less pretty. (Thanks @Charlesism)

eLillie
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0

Perhaps you can try finite, for example,

let x:CDouble = 0.1
finite(x) // which return a CInt
shucao
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0

For Float values,

import UIKit

typealias Space = Float

var MaxSpaceSize = Space.infinity

var space:Space = 1100

space = space * 2
Durul Dalkanat
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