Reified predicates

const { adt, match } = require("@masaeedu/adt") // First, we build a language of references and predicates const ref = adt({ lit: ["some literal value"], key: ["the name of some field"] }) const { lit, key } = ref const predicate = adt({ and: ["predicate", "predicate"], or: ["predicate", "predicate"], equals: ["ref", "ref"] }) const { and, or, equals } = predicate // Then we construct an expression in this language // NB: you could also use a parsing library to parse this out of a string const yourpredicate = or (equals (key ("key1")) (key ("key2"))) (and (equals (key ("last")) (lit ("Smith"))) (equals (key ("gender")) (lit ("m")))) console.log(yourpredicate) // Then we interpret our language into an actual predicate on some value const resolve = ref.match({ lit: v => _ => v, key: k => a => a[k] }) const interpret = predicate.match({ and: f => g => a => interpret(f)(a) && interpret(g)(a), or: f => g => a => interpret(f)(a) || interpret(g)(a), equals: r1 => r2 => a => resolve(r1)(a) === resolve(r2)(a) }) const inputs = [ { key1: "foo", key2: "bar", last: "Smith", gender: "m" }, // => true { key1: "foo", key2: "foo", last: "Hurpenglurper", gender: "m" }, // => true { key1: "foo", key2: "bar", last: "Hurpenglurper", gender: "m" } // => false ] const p = interpret(yourpredicate) console.log(inputs.map(p))