[swift-users] Hexadecimal floating-point literals

Toni Suter tonisuter at me.com
Sun Jun 26 02:50:59 CDT 2016


I have a question regarding hexadecimal floating-point literals. According to the Lexical Structure (https://developer.apple.com/library/prerelease/content/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html <https://developer.apple.com/library/prerelease/content/documentation/Swift/Conceptual/Swift_Programming_Language/LexicalStructure.html>) 
it is not possible to have a hex floating-point literal without the exponent. At first I thought this makes sense.
How else would the lexer / parser know if 0x123.beef is a hex floating-point literal or a hex integer literal with a property 'beef'?
However, if I define such a property on Int, it doesn’t work:

extension Int {
    var beef: Int {
        return 42

print(12.beef) 		// works
print(0b1001.beef) 	// works
print(0o77.beef) 	// works
print(0xabc.beef) 	// error: hexadecimal floating point literal must end with an exponent

Is this just to avoid confusion for the programmer? Or is there some other reason?

Thanks and best regards,
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