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Task/Monads-Maybe-monad/J/monads-maybe-monad.j

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+NB. monad implementation:
+unit=: <
+bind=: (@>)( :: ])
+
+NB. monad utility
+safeVersion=: (<@) ( ::((<_.)"_))
+safeCompose=:dyad define
+  dyad def 'x`:6 bind y'/x,unit y
+)
+
+NB. unsafe functions (fail with infinite arguments)
+subtractFromSelf=: -~
+divideBySelf=: %~
+
+NB. wrapped functions:
+safeSubtractFromSelf=: subtractFromSelf safeVersion
+safeDivideBySelf=: divideBySelf safeVersion
+
+NB. task example:
+     safeSubtractFromSelf bind safeDivideBySelf 1
+┌─┐
+│0│
+└─┘
+     safeSubtractFromSelf bind safeDivideBySelf _
+┌──┐
+│_.│
+└──┘