import { assign } from "../generics/generics.js";
import { makeGeneric } from "../generics/generics.js";
import { fnType } from "../metacircular.js";
import { Double, Int } from "../primitives/symbols.js";
import { getMul, NumInstances } from "./num.js";
import { numDictType } from "./num_type.js";

const square = numDict => x => getMul(numDict)(x)(x);

const squareFnType = makeGeneric(a => 
  fnType({
    in: numDictType(a),
    out: fnType({
      in: a,
      out: a,
    }),
  }));

// should be: Int -> Int
console.log(assign(squareFnType, makeGeneric(() => numDictType(Int))));

// should be: Double -> Double
console.log(assign(squareFnType, makeGeneric(() => numDictType(Double))));

// to call 'square' we need:
//   - access to a mapping from types to their typeclass instantiation
//   - to know that our argument is 'Int'
console.log(square(NumInstances.get(Int))(42n)); // 1764n