CODEWITHSUNDEEP
phpfloating-pointprintf
jerrygarciuh
jerrygarciuh

Reputation: 22008

sprintf() to truncate and not round a float to x decimal places?

When calculating a golf handicap differential you are supposed to truncate the answer to 1 decimal place without rounding. No idea why but...

I know how to do this using TRUNCATE() in mySQL 

 SELECT TRUNCATE( 2.365, 1 );
// outputs 2.3

but I was wondering if sprintf() could do this? The only way I know to work with decimal places in a float is ...

echo sprintf("%.1f", 2.365);
// outputs 2.4

Upvotes: 1

Views: 19797

Answers (2)

wesnick
wesnick

Reputation: 61

I find it easier to use string operations: let sprintf round to an extra significant digit, trim, then convert back to a float

    function truncate_float(float $float, int $significantDigits = 4): float
    {
        $format = sprintf('%%.%df', $significantDigits + 1);

        return (float) substr(sprintf($format, $float), 0, -1);
    }

Upvotes: 1

Darryl
Darryl

Reputation: 6217

What language is this in? Assuming it's C or one of its derivatives, and assuming you always want exactly one decimal place, and assuming your values are always non-negative, you can do this:

float val = 12.3456;
val = floor(val*10.0)/10.0;
sprintf("%.1f", val);

Is there a better way? Probably. This is just what comes to mind.

Upvotes: 8

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