On 24 December 2010 18:24, Henning Thielemann <lemming@henning-thielemann.de> wrote:

On Fri, 24 Dec 2010, Aaron Gray wrote:

The compiler is requesting an instance declaration for Show :-

  expr-eval.hs:334:23:
      No instance for (Show ([(String, Int)] -> Int))
        arising from a use of `print' at expr-eval.hs:334:23-27
      Possible fix:
        add an instance declaration for (Show ([(String, Int)] -> Int))
      In the first argument of `(.)', namely `print'
      In the second argument of `(>>=)', namely `print . calc . lexer'
      In the expression: getContents >>= print . calc . lexer

... maybe 'calc' needs a further argument?