Re: [Haskell-cafe] do ghci

On Wed, Oct 11, 2006 at 05:13:13PM -0700, Greg Fitzgerald wrote:

To: Haskell Cafe From: Greg Fitzgerald Date: Wed, 11 Oct 2006 17:13:13 -0700 Subject: [Haskell-cafe] do ghci

Just curious, why does ghci run in the context of a 'do'?

This tripped me up when I first started learning Haskell. It's fine once you know what's going on, but why the restriction? Why can't I write the code below without 'let' and ':module'?

...

two = 1 + 1 import Data.List cols = transpose [[1,2,3], [4,5,6]]

If you interact with a command line, it is natural to have IO side effects and evaluate the command lines in the order of appearance. ghci is sort of a command line, right? It is straight-forward enough to make up something ad hoc without using the concept of monadic IO and memory modification, but why? matthias