Calculate constant E value

I am doing a calculation in Objective-C. I have one value 4.0468564224e-33. I dont know what that e constant's value is. Please h开发者_开发百科elp me: how can I calculate this constant value? How are constant values declared and calculated in Objective-C?

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The e is part of scientific notation.

Most calculators and many computer programs present very large and very small results in scientific notation. Because superscripted exponents like 10⁷ cannot always be conveniently represented on computers, typewriters and calculators, an alternative format is often used: the letter E or e represents times ten raised to the power of, thus replacing the × 10, followed by the value of the exponent. Note that the character e is not related to the mathematical constant e (a confusion that is less likely with capital E); and though it stands for exponent, the notation is usually referred to as (scientific) E notation or (scientific) e notation, rather than (scientific) exponential notation (though the latter also occurs).

4.0468564224e-33 means 4.0468564224 * 10^-33, or 0.0000000000000000000000000000000040468564224.

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Adding this citation for future users which is reverse of the asked above question. Google brought me here, So I think this is the best place to add this answer.

NSString *num = @"5.0E0";

To get the processed value from above string you need to simply do this:

CGFloat secNum = [num floatValue]; // this will feed 5 to secNum

Hope it could help someone.

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If you just need to use e's value you can get it from math.h

#import <math.h>
...

NSLog(@"e: %g", M_E);