[Haskell-cafe] ACross

[Udo Stenzel]

Jenny678 wrote:
> Can somebody help me
> My Problem is to define a code for:
> 
> >cross 7         -- means 7*7
> >+++++++
> >++      ++
> >+  +  +  +
> >+    +    +
> >+  +  +  +
> >++      ++
> >+++++++

As always, try to decompose a hard problem into simple steps.  It's
probably adequate to represent pictures as

*> type Picture = [String]

then compose your "cross" from six lines.  An overlay operator

*> over :: Picture -> Picture -> Picture

is trivial to write.  Creating the lines should be easy, 

*> replicate :: Int -> a -> [a]

from the Prelude and list comprehensions might help.


> Can I use putString ???

Of course, but you shouldn't.  Creating a cross is a seperate step from
putting it on screen.  "cross" should probably return a list of Strings
or a single String (think "unlines").  In fact,

*> cross :: Int -> Picture

definitely makes the most sense to me.


Udo.
-- 
People with great minds talk about ideas.
People with ordinary minds talk about things.
People with small minds talk about other people.
	-- Eleanor Roosevelt
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