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Update MicroKanren.lhs #1

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3 changes: 1 addition & 2 deletions src/MicroKanren.lhs
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Expand Up @@ -7,7 +7,6 @@ Let's get set up:

> module MicroKanren where
> import Data.List (transpose)
> import Data.Maybe (fromMaybe)

These occur up at the front mostly for bookkeeping. I'll explain them where they're used later.

Expand All @@ -31,7 +30,7 @@ Turns out all we need to represent a logic var is a kind of ID, which I don't th
Logic programs output pairs of variable bindings that satisfy the input program (proram is another word here for list of equations or constraints). We call a complete list of these satisfying some program a Substitution. You can think of this as an associative list, where each pair is the first element set equal to the second element.

> walk :: Substitution -> Term -> Term
> walk s x@(Var _) = fromMaybe x $ fmap (walk s) $ lookup x s
> walk s x@(Var _) = maybe x (walk s) (lookup x s)
> walk _ x = x

When we want to find out what a variable is referring to in our substitution, we use walk. Walk is so-called because it recursively looks up any transitive definitions, e.g. X = Y = Z, spitting out Z when asked what X means. Here's an example:
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