But...suppose we had a spreadsheet a little like Haskell where each

cell has a static type, and the values can be Haskell functions. What

interesting things could we do with it that we couldn't do with Excel?

I had a MSc student doing something in this direction some years ago. He

made a Haskell interface which was intended to work like a spreadsheet. In

this interface, every declaration has a value window (if the entity declared

has a showable type) and a declaration window. A designated button triggers

a recompilation, and thus also a recalculation of all declared values -

this, I think, captures the essence of spreadsheets which is to be able to

make changes and quickly see the results. In order to support the kind of

array omputations often done in spreadsheets, an extended array module was

defined which declares a number of array functions and other conveniences.

See http://www.mrtc.mdh.se/index.php?choice=projects&id=0041.