I'm writing a simple game engine in Clojure, and each game object supplies
its own unique update function, which takes the original object (a map of
properties) and returns an updated version. However, writing the updates
is somewhat cumbersome because each line of code has to return either the
original or updated object. I'd like to see if I can clean up this code,
possibly by using monads (which I don't understand very well). Does anyone
have any advice? Thanks (Code examples below)
The pseudocode for what i want to do looks something like this:
if left key is held
g.position += [-10 0]
if right key is held
g.position += [10 0]
if up key is held
g.position += [0 -10]
if down key is held
g.position += [0 10]
if q is pressed
fire event {:type :dialogue, :text "Hello"}
if space is pressed
g.switchstate(:s2)
But the code I ended up writing is this mess:
(fn [g]
(-> g
(#(if (@*keys-held* :left)
(update-in % [:position] v+ [-10 0])
%))
(#(if (@*keys-held* :right)
(update-in % [:position] v+ [10 0]) %))
(#(if (@*keys-held* :up)
(update-in % [:position] v+ [0 -10]) %))
(#(if (@*keys-held* :down)
(update-in % [:position] v+ [0 10]) %))
(#(if (@*keys-pressed* \q)
(do (fire-event {:type :dialogue
:text "Hello!"})
%)
%))
(#(if (@*keys-pressed* :space)
(do (comment (println "spaced!"))
(switch-state % :s2)) %))))
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