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+# Laziness
+
+Due to the call-by-need reduction order of bruijn, several operations
+are lazily evaluated (automagically!).
+
+## Infinite lists
+
+You can use infinite list generators like `repeat`{.bruijn} or
+`iterate`{.bruijn} to lazily interact with list elements.
+
+``` bruijn
+:import std/List .
+
+:test (length (take (+3) (repeat (+4)))) ((+3))
+:test (take (+5) (iterate ++‣ (+0))) (((+0) : ((+1) : ((+2) : ((+3) : {}(+4))))))
+```
+
+## Math
+
+``` bruijn
+# power function
+:test ((iterate (…⋅… (+2)) (+1)) !! (+3)) ((+8))
+
+# prime numbers
+primes nub ((…≠?… (+1)) ∘∘ gcd) (iterate ++‣ (+2)) ⧗ (List Number)
+
+:test (take (+4) primes) ((+2) : ((+3) : ((+5) : {}(+7))))
+
+# fibonacci
+fibs head <$> (iterate [~0 : (^0 + ~0)] ((+0) : (+1))) ⧗ (List Number)
+
+:test (take (+4) primes) ((+0) : ((+1) : ((+1) : {}(+2))))
+```
+
+## Optimization
+
+Laziness can (in some cases) produce huge performance boosts. For
+example:
+
+``` bruijn
+# 11 seconds
+:time (+10) ** (+500)
+
+# 0.1 seconds
+:time ((+10) ** (+500)) =? (+400)
+```
+
+This works because a ternary number is just a list of trits which (in
+this case) gets recursively generated by the `pow`{.bruijn} function.
+The `eq?`{.bruijn} function just throws away the first argument if it's
+already clear that the numbers can't be equal (in this case after the
+first argument got bigger than `(+400)`{.bruijn}).