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(meditations
"Sequence comprehensions can bind each element in turn to a symbol"
(= [0 1 2 3 4 5]
(for [index (range 6)]
index))
"They can easily emulate mapping"
(= '(0 1 4 9 16 25)
(map (fn [index] (* index index))
(range 6))
(for [index (range 6)]
(* index index)))
"And also filtering"
(= '(1 3 5 7 9)
(filter odd? (range 10))
(for [index (range 10) :when (odd? index)]
index))
"And they trivially allow combinations of the two transformations"
(= '(1 9 25 49 81)
(map (fn [index] (* index index))
(filter odd? (range 10)))
(for [index (range 10) :when (odd? index)]
(* index index)))
"More complex transformations can be formed with multiple binding forms"
(= [[:top :left] [:top :middle] [:top :right]
[:middle :left] [:middle :middle] [:middle :right]
[:bottom :left] [:bottom :middle] [:bottom :right]]
(for [row [:top :middle :bottom] column [:left :middle :right]]
[row column])))