PureScript 遅延評価
Control.Lazy
https://pursuit.purescript.org/packages/purescript-control/5.0.0/docs/Control.Lazy
Data.Lazy
https://pursuit.purescript.org/packages/purescript-lazy/5.0.0/docs/Data.Lazy#v:force
https://book.purescript.org/chapter11.html
https://blog.drewolson.org/laziness-in-purescript
遅延評価