Gwern Branwen wrote:

On Wed, Jan 6, 2010 at 7:23 PM, Tony Morris wrote:

...

ghc -e "import Control.Monad; forM [[1,2,3]] reverse"

As of 6.10.2, the bug whereby the GHC API lets you use functions from anywhere just by naming them (Java-style) has not been fixed:

$ ghc -e "Control.Monad.forM [[1,2,3]] reverse" package flags have changed, resetting and loading new packages...

<interactive>:1:25: Warning: Defaulting the following constraint(s) to type `Integer' `Num t' arising from the literal `3' at <interactive>:1:25 In the expression: 3 In the expression: [1, 2, 3] In the first argument of `forM', namely `[[1, 2, 3]]'

<interactive>:1:25: Warning: Defaulting the following constraint(s) to type `Integer' `Num t' arising from the literal `3' at <interactive>:1:25 In the expression: 3 In the expression: [1, 2, 3] In the first argument of `forM', namely `[[1, 2, 3]]' [[3],[2],[1]] it :: [[Integer]] (0.01 secs, 1710984 bytes)

I see the same on GHC 6.10.4. $ ghc -e "Control.Monad.forM [[1,2,3]] reverse" [[3],[2],[1]] What would it be fixed to? What is wrong with how it is? -- Tony Morris http://tmorris.net/

On Wed, 6 Jan 2010, Gwern Branwen wrote:

On Wed, Jan 6, 2010 at 7:23 PM, Tony Morris wrote:

...

ghc -e "import Control.Monad; forM [[1,2,3]] reverse"

As of 6.10.2, the bug whereby the GHC API lets you use functions from anywhere just by naming them (Java-style) has not been fixed:

$ ghc -e "Control.Monad.forM [[1,2,3]] reverse" package flags have changed, resetting and loading new packages...

Why is this a bug? This is the intended behaviour in GHCi and you can include and exclude packages with -package and -hide-package options, respectively.

On Wed, Jan 6, 2010 at 6:15 PM, Reid Barton wrote:

On Thu, Jan 07, 2010 at 10:23:35AM +1000, Tony Morris wrote:

...

Can I import a module when using ghc -e?

e.g. ghc -e "import Control.Monad; forM [[1,2,3]] reverse"

One option is to create a file "imports.hs" which contains the text "import Control.Monad", and then run

ghc -e "forM [[1,2,3]] reverse" imports.hs

I use this method in a short shell script "interact" so that I can apply Haskell functions to files from the command line and don't have to type the full qualified names of things in modules I use frequently.

Did you know you can put commands in $HOME/.ghci that will be loaded every time you run ghci? So, if you have modules that you commonly use put something like: :m + Control.Monad In your $HOME/.ghci file and then you can use ghci instead of this ghc -e trick. HTH, Jason