52 lines
1.5 KiB
Plaintext
52 lines
1.5 KiB
Plaintext
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open RescriptMocha
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open Mocha
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open Parsec
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describe("expressions of plus and times", () => {
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let rec expr: lazy_t<t<int>> = lazy(bind(
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Lazy.force(term),
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t => choice(
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bind(Primitive.symbol("+"), _ => bind(
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Lazy.force(expr),
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e => returnP(t + e)
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)),
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returnP(t)
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)
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))
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and term: lazy_t<t<int>> = lazy(bind(
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Lazy.force(factor),
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f => choice(
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bind(Primitive.symbol("*"), _ => bind(
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Lazy.force(term), t => returnP(f * t)
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)),
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returnP(f)
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)
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))
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and factor: lazy_t<t<int>> = lazy(choice(bind(Primitive.symbol("("), _ => bind(
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Lazy.force(expr), e => bind(Primitive.symbol(")"), _ => returnP(e))
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)), Primitive.natural))
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let eval: string => int = xs => switch parse(Lazy.force(expr), xs) {
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| list{(n, "")} => n
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| list{(_, out)} => raise(Wrongo(`unconsumed input ${out}`))
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| list{} => raise(Wrongo("invalid input"))
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| _ => raise(Wrongo(wrongoMessage))
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}
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it("equals 3 at 1 + 2", () => {
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Assert.deep_equal(eval("1 + 2"), 3)
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})
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it("equals 10 at 2 * 3 + 4", () => {
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Assert.deep_equal(eval("2 \n * 3 \t +4"), 10)
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})
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it("equals 14 at 2 *(3 + 4)", () => {
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Assert.deep_equal(eval("2 *(3 + 4)"), 14)
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})
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// it("raises Wrongo(unconsumed input -4) at 2*3-4", () => {
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// Assert.throws(() => eval("2*3-4"), Js.Exn.asJsExn(Wrongo("unconsumed input -4")))
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// })
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// it("raises Wrongo(invalid input) at -1", () => {
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// Assert.throws(() => eval("-1"), Js.Exn.asJsExn(Wrongo("invalid input")))
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// })
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})
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