change.m

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
	NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

	NSDecimalNumber *price  = [NSDecimalNumber decimalNumberWithString:@"4.0"];
	NSDecimalNumber *paid   = [NSDecimalNumber decimalNumberWithString:@"3.1"];
	NSDecimalNumber *result = [price decimalNumberBySubtracting: paid];
	
	//NSLog([result stringValue]);
	NSLog(@"change = %@",[result stringValue]);
	[pool drain];
	return 0;
}

change.scala

object SquareChange {

   def main(args: Array[String]) {
     val price = BigDecimal("4.0");
     val paid  = BigDecimal("3.1");
     val change = price - paid;
     println("change = " + change);
     
   }

}

First Solution.c

int main() {
	int dollars, cents;
	float paid = 4.00f;
	float price =  3.10f;
	
	int paidInt = paid * 100;
	int priceInt = price * 100;
	
	int changeInt = paidInt -  priceInt;
	
	dollars = (float)changeInt / 100;
	cents = changeInt % 100;
	
	printf("change = %d.%d\n", dollars, cents);
        return 0;
}

gistfile3.c

/*    
 * If you pay $4.00 for a latte that costs    
 * $3.10, how much change do you get?    
 */

int main() {
  float change = 4.00f - 3.10f;
  printf("change = %10.10f\n", change);
  return 0;
}

// => 0.9000000954

other.c

#include <stdio.h>

int main() {
  float floating = 4.00 - 3.10;
  printf("float = %10.10f\n", floating);

  double doubled = 4.00 - 3.10;
  printf("double = %10.10f\n", doubled);

  printf("float size = %zu\n", sizeof(floating));
  printf("double size = %zu\n", sizeof(doubled));

  return 0;
}