BTW: There isn't an easy way to magically derive opTable. We're relying
on the fact that these simple functions all have the same type.
Ben Lippmeier wrote:
opTable
= [ ("+", (+))
, ("-", (-)) ... ]
myeval x y op
= let Just fun = lookup op opTable
in x `fun` y
You could also do
myeval x y op
= case op of
"+" -> x + y
"-" -> x - y
...
is probably the "smallest" way.
Ben.
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