On Sat, Jul 31, 2010 at 4:56 PM, michael rice
From: http://en.wikibooks.org/wiki/Haskell/Laziness
Given two functions of one parameter, f and g, we say f is stricter than g if f x evaluates x to a deeper level than g x
Exercises
1. Which is the stricter function?
f x = length [head x] g x = length (tail x)
Prelude> let f x = length [head x] Prelude> let g x = length (tail x) Prelude> f undefined 1 Prelude> g undefined *** Exception: Prelude.undefined Prelude>
So, g is stricter than f?
Wouldn't both functions need to evaluate x to the same level, *thunk* : *thunk* to insure listhood?
f x = length [head *thunk* : *thunk*] g x = length (tail *thunk* : *thunk*)
Michael
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Notice the two different kinds of brackets being used in f versus g :)