Using the new ArrayBuffer access arrays, it is actually possible to retrieve the exact mantissa and exponent, by extracting them from the Uint8Array. If you need more speed, consider reusing the Float64Array. function getNumberParts(x) { var float = new Float64Array(1), bytes = new Uint8Array(float.buffer); float[0] = x; var sign = bytes[7] >> 7, exponent = … Read more
It’s probably best to look at what SafeHaskell allows: Safe Language The Safe Language (enabled through -XSafe) restricts things in two different ways: Certain GHC LANGUAGE extensions are disallowed completely. Certain GHC LANGUAGE extensions are restricted in functionality. Below is precisely what flags and extensions fall into each category: Disallowed completely: GeneralizedNewtypeDeriving, TemplateHaskell Restricted functionality: … Read more
It’s because the pattern matching is incomplete. There’s no guarantee that one of x==a, x<a, or x>a holds. For instance, if the type is Double and x is NaN then none of them are True.
Let’s start with a code example: foob :: forall a b. (b -> b) -> b -> (a -> b) -> Maybe a -> b foob postProcess onNothin onJust mval = postProcess val where val :: b val = maybe onNothin onJust mval This code doesn’t compile (syntax error) in plain Haskell 98. It requires … Read more
A complete example Here’s a little example that shows the situation: module A where big :: () -> [Int] big _ = [1..10^7] Looks like a function, right? But what does GHC do? It floats the enum to the top level! A.big1 :: [Int] [ Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=0, Value=False, ConLike=False, Cheap=False, Expandable=False, Guidance=IF_ARGS [] 7 … Read more
In general, fusion refers to transformations whose purpose is to get rid of intermediate data structures. You fuse function calls that result in wasteful memory allocations into something more efficient. This is actually IMO one of the biggest applications of Haskell being pure. And you pretty much don’t need to do anything to get it, … Read more
This is because ghci disables buffering, while a program compiled with ghc has line buffering by default. You can see this by running this: import System.IO main = print =<< hGetBuffering stdout In ghci you see NoBuffering while with runghc you get LineBuffering. Since the newline character doesn’t print until after the user input, the … Read more
Let’s see what’s going on, try $ du -hs A 13M A $ file A A: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.27, not stripped $ ldd A linux-vdso.so.1 => (0x00007fff1b9ff000) libXrandr.so.2 => /usr/lib/libXrandr.so.2 (0x00007fb21f418000) libX11.so.6 => /usr/lib/libX11.so.6 (0x00007fb21f0d9000) libGLU.so.1 => /usr/lib/libGLU.so.1 (0x00007fb21ee6d000) libGL.so.1 => /usr/lib/libGL.so.1 … Read more
GHC Core is the System FC language into which all Haskell is translated. The (approximate) grammar for Core is given by: Core is closely related to the simpler and better known System F. All transformations GHC does on the Core level are type-preserving refactorings of this Core representation, to improve performance. And, not so well … Read more
GHC does not memoize functions. It does, however, compute any given expression in the code at most once per time that its surrounding lambda-expression is entered, or at most once ever if it is at top level. Determining where the lambda-expressions are can be a little tricky when you use syntactic sugar like in your … Read more