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Re: BOOLs, definition of YES
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Re: BOOLs, definition of YES


  • Subject: Re: BOOLs, definition of YES
  • From: Stéphane Sudre <email@hidden>
  • Date: Tue, 20 May 2003 16:27:07 +0200

On mardi, mai 20, 2003, at 16:01 Europe/Paris, Tom Sutcliffe wrote:

Sorry this is a minor Java/C types whinge but I'm interested in how others approach this.

Coming from Java I'm used to having booleans as a distinct type, and for the ! operator to work correctly on them. So in Obj-C I was surprised to find that because of YES and NO being defined as 1 and 0, YES doesn't equal !!YES.

I'm therefore interested in how best to go about inverting a BOOL variable. I stuck with

flag = (flag ? NO : YES);
// flag = 1 - flag would also work but is even less clear

Uh ?

I might be missing something in your explanation but this code is working fine:

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
BOOL truetrue=YES;
BOOL falsefalse=NO;

truetrue=!truetrue;
falsefalse=!falsefalse;

if (truetrue==NO)
{
NSLog(@"!YES == NO");
}

if (falsefalse==YES)
{
NSLog(@"!NO == YES");
}

// insert code here...

[pool release];
return 0;
}

I also tested !!YES and it is YES.
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 >BOOLs, definition of YES (From: Tom Sutcliffe <email@hidden>)

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