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macOS Kochan Exercise 4-4

V

veshman

macrumors newbie
Original poster
Sep 21, 2005
10
0
Hi, I'm very new to programming and was wondering if I could get some help on this problem. I'm working through Kochan's 2.0 book, and am getting an error on problem 4-4, as shown in the image.


If I make x an integer, the program seems to run fine. But if I make it a float, it errors with "invalid operands to binary ^"
 

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lee1210

lee1210

macrumors 68040
Jan 10, 2005
3,182
3
Dallas, TX
^ is not the exponentiation operator, it is the bitwise XOR operator. There is, in fact, no exponentiation operator. There is a pow function in math.h for dealing with doubles. For integers, for powers of 2, you can use << to shift left. For other integers... you have to do it yourself.

-Lee

EDIT: For simple, fixed powers, just multiply the appropriate number of times.
 
M

mdeh

macrumors 6502
Jan 3, 2009
345
2
veshman said:
Hi, I'm very new to programming and was wondering if I could get some help on this problem. I'm working through Kochan's 2.0 book, and am getting an error on problem 4-4, as shown in the image.


If I make x an integer, the program seems to run fine. But if I make it a float, it errors with "invalid operands to binary ^"
Click to expand...

As Lee said below, just use simple substitution. You have not yet used Pow or shift ( << ) operators.

So,

Code: 
#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	/* 3x³ - 2x² + 6  for x = 2.55 */
	
	float x = 2.55;
	
	NSLog(@"Given x = 2.55\n");
    NSLog(@" 3x³ - 2x² + 6 = %f:", 3 * (x * x * x) - 2 *( x * x) + 6);
    [pool drain];
    return 0;
}
 
V

veshman

macrumors newbie
Original poster
Sep 21, 2005
10
0
Thanks much!

Thanks a lot for your responses!

That makes sense.....I thought I was missing something big. And as you pointed out, I'm thus far unfamiliar with powf and bit operations (read about them, but haven't used them).

Bhavesh
 
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