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A collection of utilities for representing and manipulating time series and such.

There is a newer version: 0.1.6

package com.unit16.z.function;

import java.util.HashMap;
import java.util.function.Function;

public final class HashCache 
implements Function
{
	private final HashMap cache_ = new HashMap<>();
	
	/**
	 * Must be referentially transparent:
	 */
	private final Function f_;
	
	public HashCache(Function f) { f_ = f; }

	@Override
	public Y apply(X from) {
		if (!cache_.containsKey(from))
		{
			cache_.put(from, f_.apply(from));
		}
		return cache_.get(from);
	}
}