Because (,) is a constructor, the difference makes no difference to Haskell’s semantics (:sprint gives access to internal thunk implementation details so doesn’t count.) So this is a question of which optimizations and trade-offs GHC does when compiling (x,x) in different positions. Someone else may know the precise reason in these cases.
GHCi looks for its configuration file at ~/.ghc/ghci.conf on Unix-like systems. %APPDATA%\ghc\ghci.conf on Windows. The configuration file syntax is simple: it’s a list of GHCi commands to execute on startup. For example, your ghci.conf could contain: import Control.Applicative import Data.Char import Data.List :set prompt “> ” The last line sets the prompt to “> ” … Read more
You can also set the command line arguments in ghci ghci> :set args foo bar ghci> main or ghci> :main foo bar
GHC only knows about packages that are installed. To see which packages are installed, use the ghc-pkg list command: $ ghc-pkg list /usr/lib/ghc-6.12.1/package.conf.d: Cabal-1.7.4 array-0.2.0.1 base-3.0.3.0 base-4.2.0.0 bin-package-db-0.0.0.0 binary-0.5.0.1 bytestring-0.9.1.4 containers-0.2.0.1 directory-1.0.0.2 (dph-base-0.4.0) (dph-par-0.4.0) (dph-prim-interface-0.4.0) (dph-prim-par-0.4.0) (dph-prim-seq-0.4.0) (dph-seq-0.4.0) extensible-exceptions-0.1.1.0 ffi-1.0 filepath-1.1.0.1 (ghc-6.12.1) ghc-prim-0.1.0.0 haskeline-0.6.2 haskell98-1.0.1.0 hpc-0.5.0.2 integer-gmp-0.1.0.0 mtl-1.1.0.2 old-locale-1.0.0.1 old-time-1.0.0.1 pretty-1.0.1.0 process-1.0.1.1 random-1.0.0.1 rts-1.0 syb-0.1.0.0 … Read more
This is a known limitation of dynamic linking object files in the bytecode interpreter, GHCi. If you load compiled code that was statically linked against a given C object, and then also interpret some Haskell on the fly that also refers via the FFI to the same C object, the runtime linker will be forced … Read more
Have you tried adding :set prompt “ghci> ” to ~/.ghci?
Let’s assume you have a mylib library, and mylib-commandline and mylib-server executables. You use hs-source-dirs for the library and each executable so that each has their own project root, avoiding double compilation: mylib/ # Project root mylib.cabal src/ # Root for the library tests/ mylib-commandline/ # Root for the command line utility + helper modules … Read more
This is not a function code, it’s function signature which can only be saved in a module along with function definition and the be loaded to GHCi. This signature means that you’re going to define a function lucky which gets an Integer and returns a String. However if you’re composing your functions using GHCi as … Read more
Not currently. The closest command to what you want is :info :info name … Displays information about the given name(s). For example, if name is a class, then the class methods and their types will be printed; if name is a type constructor, then its definition will be printed; if name is a function, then … Read more
When you are stopped at a breakpoint in GHCi, you can access anything that’s in scope. Let’s say you have a function like this: foo :: Int -> Int foo x = g (x + 2) where g y = x^y You can set a breakpoint on foo and try calling it: > :break foo … Read more