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The Hydra language for strongly-typed transformations

There is a newer version: 0.8.0

package hydra.lib.maps;

import hydra.Flows;
import hydra.compute.Flow;
import hydra.core.Name;
import hydra.core.Term;
import hydra.core.Type;
import hydra.dsl.Expect;
import hydra.dsl.Terms;
import hydra.graph.Graph;
import hydra.tools.PrimitiveFunction;
import java.util.HashMap;
import java.util.List;
import java.util.function.Function;

import static hydra.Flows.pure;
import static hydra.dsl.Types.function;
import static hydra.dsl.Types.lambda;
import static hydra.dsl.Types.map;


public class MapKeys extends PrimitiveFunction {
    public Name name() {
        return new Name("hydra/lib/maps.mapKeys");
    }

    @Override
    public Type type() {
        return lambda("k1", lambda("k2", lambda("v",
            function(function("k1", "k2"), map("k1", "v"), map("k2", "v")))));
    }

    @Override
    protected Function, Flow> implementation() {
        return args -> Flows.map(
            Expect.map(k -> pure(Terms.apply(args.get(0), k)), Flows::pure, args.get(1)), Terms::map);
    }

    public static  Function, java.util.Map> apply(Function mapping) {
        return (arg) -> apply(mapping, arg);
    }

    /**
     * Apply the function to both arguments.
     */
    public static  java.util.Map apply(Function mapping, java.util.Map arg) {
        java.util.Map result = new HashMap<>();
        for (java.util.Map.Entry e : arg.entrySet()) {
            result.put(mapping.apply(e.getKey()), e.getValue());
        }
        return result;
    }
}