Variadic function and NSComparator example

vac.m

/*
  curl -kOs https://raw.github.com/gist/1550857/vac.m && cc -framework Cocoa -o vac vac.m && ./vac
  For http://stackoverflow.com/questions/8693810/objective-c-possible-shorter-if-notation
  Variadic function and NSComparator example.
*/
#import <Cocoa/Cocoa.h>
#import <stdarg.h>
#import <stdio.h>

// This is just a simple object equality comparator.
static NSComparator compareeq = ^(id obj1, id obj2) {
  if (obj1 == obj2) {
    return (NSComparisonResult)NSOrderedSame;
  }
  return (NSComparisonResult)NSOrderedDescending;
};

// This'll execute the above comparator to compare eq to each object in args.
NSComparisonResult comparatorV(NSComparator compare, NSObject *eq, va_list args) {
  NSComparisonResult result;
  NSObject *value;
  do {
    if (value = va_arg(args, NSObject*)) {
      result = compare(eq,value);
    }
  } while (value && result == NSOrderedSame);
  return (!value?NSOrderedDescending:NSOrderedSame);
}

// This test if eq is == to all the subsequent objects passed.
// The first parameter MUST not be nil and isn't used for comparisons.
// If any object passed is nil it'll end the comparison.
BOOL isEqualTo(NSObject* eq, ...) {
  va_list args;
  va_start(args, eq);
  BOOL result = (NSOrderedSame != comparatorV(compareeq,eq,args));
  va_end(args);
  return result;
}

// This'll just test if each object passed is == [NSNull null].
// The first parameter MUST not be nil and isn't used for comparisons.
// If any object passed is nil it'll end the comparison.
BOOL isNSNull(NSObject *o, ...) {
  NSNull *n = [NSNull null];
  if (NSOrderedSame != compareeq(n,o)) return NO;
  va_list args;
  va_start(args, o);
  BOOL result = (NSOrderedSame != comparatorV(compareeq,n,args));
  va_end(args);
  return result;
}

#define YN(p) (p?"PASS":"FAIL")

#define IS_NSNULL(p) printf("%s\n",YN(p == isNSNull(a,b,c,nil)))
#define ALL_ARE_NSNULL IS_NSNULL(YES)
#define ALL_ARE_NOT_NSNULL IS_NSNULL(NO)

#define IS_EQUAL(p) printf("%s\n",YN(p == isEqualTo(a,b,c,nil)))
#define ALL_ARE_EQUAL IS_EQUAL(YES)
#define ALL_ARE_NOT_EQUAL IS_EQUAL(NO)

int main(int argc, char* argv[]) {
  NSObject *a,*b,*c;
  {
    a =[[NSObject alloc] init];
    b =[[NSObject alloc] init];
    c =[[NSObject alloc] init];
    ALL_ARE_NOT_NSNULL;
  } {
    a =[NSNull null];
    b =[[NSObject alloc] init];
    c =[NSNull null];
    ALL_ARE_NOT_NSNULL;
  } {
    a =[NSNull null];
    b =[NSNull null];
    c =[NSNull null];
    ALL_ARE_NSNULL;
  } {
    a =[NSNull null];
    b =[[NSObject alloc] init];
    c =[[NSObject alloc] init];
    ALL_ARE_NOT_NSNULL;
  } {
    a =[NSNull null];
    b =[NSNull null];
    c =[[NSObject alloc] init];
    ALL_ARE_NOT_NSNULL;
  } {
    a =[NSNull null];
    b =[[NSObject alloc] init];
    c =nil;
    ALL_ARE_NOT_NSNULL;
  } {
    a =[NSNull null];
    b =[NSNull null];
    c =nil;
    ALL_ARE_NSNULL;
  } {
    a =[NSNull null];
    b =nil;
    c =[NSNull null]; // This'll never be tested because comparison stops with b.
    ALL_ARE_NSNULL;
  }

  printf("\n");

  {
    a =[[NSObject alloc] init];
    b =[[NSObject alloc] init];
    c =[[NSObject alloc] init];
    ALL_ARE_NOT_EQUAL;
  } {
    a =[NSNull null];
    b =[[NSObject alloc] init];
    c =[NSNull null];
    ALL_ARE_NOT_EQUAL;
  } {
    a =[NSNull null];
    b =[NSNull null];
    c =[NSNull null];
    ALL_ARE_EQUAL;
  } {
    a =b=c=[[NSObject alloc] init];
    ALL_ARE_EQUAL;
  } {
    a =[NSNull null];
    b =[[NSObject alloc] init];
    c =[[NSObject alloc] init];
    ALL_ARE_NOT_EQUAL;
  } {
    a =[NSNull null];
    b =[NSNull null];
    c =[[NSObject alloc] init];
    ALL_ARE_NOT_EQUAL;
  } {
    a =[NSNull null];
    b =[[NSObject alloc] init];
    c =nil;
    ALL_ARE_NOT_EQUAL;
  } {
    a =[NSNull null];
    b =nil;
    c =[NSNull null]; // This'll never be tested because comparison stops with b.
    ALL_ARE_EQUAL;
  }
}

vac.md

StackOverflow: Objective-C Possible shorter “if ” notation?

Run:

curl -kOs https://raw.github.com/gist/1550857/vac.m && cc -framework Cocoa -o vac vac.m && ./vac