const {Maybe} = require ('ramda-fantasy')
const {Just, Nothing, maybe} = Maybe
const validate = v => v === "fred" ? Just ("Y") : Nothing ()
const vv = val => Maybe (val) .chain (validate) .getOrElse ('N')
console .log ([
vv(null), // 'N'
vv('fred'), // 'Y'
vv('ding') // 'N'
])