# haskell truncate float

The function properFraction takes a real fractional number x and returns a pair (n,f) such that x = n+f, and: . The Haskell Prelude contains predefined classes, types, and functions that are implicitly imported into every Haskell program. As to GHC. In GHC-6.6.1 these examples end with a stack overflow, but if I shorten the list, the time relations remain the same. This webpage is a HTML version of most of Bernie Pope's paper A Tour of the Haskell Prelude. This isn't a haskell problem as much as a floating point problem. To make searching easy I've included a list of functions below. See Float… As far as I can judge, double2Int does the same like truncate. Float. Declare integer y and initialize it with the value of floating point number x.Ignore non-integer digits of x. * modules, I'd agree with you, those should be used as a last resort. Conversion Mania. Haskell has two main floating point types: Float and Double. And of course, ... round, truncate, and so on. @chi, ceiling, floor, truncate and fromIntegral are mentioned in the answer, so not quite sure why you brought them up. main = print . mapU (floor :: Double -> Int) \$ enumFromToFracU 0 100000000 Runs in 1 minute, 10 seconds: \$ time ./henning 5000000050000000 ./henning 70.25s … Trac metadata But it’s difficult to keep track of all the different ways to convert between values. You can also see this by calculating 0.1 + 0.2, which awkwardly returns 0.30000000000000004 instead of 0.3. instance Enum Float where succ x = x + 1 pred x = x-1 toEnum = int2Float fromEnum = fromInteger. We can see this effect in practice in any language that supports floating point, such as Haskell: > truncate (16777216 - 1 :: Float) 16777215 > truncate (16777216 + 1 :: Float) 16777216 Subtracting 1 gives us the decremented number, but adding 1 had no effect with floating point math! n is an integral number with the same sign as x; and ; f is a fraction with the same type and sign as x, and with absolute value less than 1.; The default definitions of the ceiling, floor, truncate and round functions are in terms of properFraction. Since each floating point number is implemented in a finite number of bits, there exist numbers that can't be represented completely accurately. We’ve gone over some of the conversions between similar types. You can convert a floating-point number to an Int or Integer using truncate and round. round x returns the nearest integer to x, the even integer if x is equidistant between two integers. Problem Solution Examples creating a complex number from real and imaginary rectangular components The Float type is a single-precision floating point number. Idiom #80 Truncate floating point number to integer. You can convert an Integer to a floating-point number (Float or Double) using fromInteger. Haskell/Type basics II, Float' instance Floating Double -- Defined in 'GHC. sumU . Make sure to truncate towards zero: a negative x must yield the closest greater integer (not lesser). Instead of using the methods from RealFrac I could simply use double2Int but I consider this a work-around. A Tour of the Haskell Prelude (and a few other basic functions) Authors: Bernie Pope (original content), Arjan van IJzendoorn (HTML-isation and updates), Clem Baker-Finch (updated for Haskell 98 hierarchical libraries organisation). So now, we *do* have a good rule for truncate, but floor, ceiling and round turn out to be awesomely slow. 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