CODEWITHSUNDEEP
objective-ciosfloating-pointrounding
ghiboz
ghiboz

Reputation: 8003

iOS round a float

I have a floating point number that have more decimal digits, for example:

float fRes = 10.0 / 3.0;

actually the fRes value is 3.3333333333333 it's possible set for example 2 decimal digits:

float fRes = 10.0 / 3.0;
// fRes is 3.333333333333333333333333
float fResOk = FuncRound( fRes, 2 );
// fResOk is 3.33

thanks in advance

Upvotes: 21

Views: 41829

Answers (2)

Nathan Day
Nathan Day

Reputation: 6047

I don't know where you are using this rounded number, but you should only round your value when displaying it to the user, there are C based format string ways to round floating point numbers for example

[NSString stringWithFormat:@"%.2f", value];

as you may have already read, floating point number are approximations of real numbers, so doing fResOk = roundf( fRes*100.0)/100.0; may not give you 3.33 but a number which is just as close as you can get with floating point number to 3.33.

Upvotes: 59

gaige
gaige

Reputation: 17491

Assuming that you're looking for the correct function to round to a certain number of digits, you'll probably find it easiest to do the following:

fResOk = roundf( fRes*100.0)/100.0;

That will multiply the value by 100 (giving you your 2 digits of significance), round the value, and then reduce it back to the magnitude you originally started with.

Upvotes: 30

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