PerUnit.java

// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
 
package org.wpilib.units;
 
import java.util.Objects;
import org.wpilib.units.measure.Per;

public class PerUnit<N extends Unit, D extends Unit> extends Unit {
  private final N m_numerator;
  private final D m_denominator;

  @SuppressWarnings("rawtypes")
  private static final CombinatoryUnitCache<Unit, Unit, PerUnit> cache =
      new CombinatoryUnitCache<>(PerUnit::new);

  private PerUnit(N numerator, D denominator) {
    super(
        numerator.isBaseUnit() && denominator.isBaseUnit()
            ? null
            : combine(numerator.getBaseUnit(), denominator.getBaseUnit()),
        numerator.toBaseUnits(1) / denominator.toBaseUnits(1),
        numerator.name() + " per " + denominator.name(),
        numerator.symbol() + "/" + denominator.symbol());
    m_numerator = numerator;
    m_denominator = denominator;
  }

  protected PerUnit(PerUnit<N, D> baseUnit, N numerator, D denominator) {
    super(
        baseUnit,
        numerator.toBaseUnits(1) / denominator.toBaseUnits(1),
        numerator.name() + " per " + denominator.name(),
        numerator.symbol() + "/" + denominator.symbol());
    m_numerator = numerator;
    m_denominator = denominator;
  }

  PerUnit(
      PerUnit<N, D> baseUnit,
      UnaryFunction toBaseConverter,
      UnaryFunction fromBaseConverter,
      String name,
      String symbol) {
    super(baseUnit, toBaseConverter, fromBaseConverter, name, symbol);
    m_numerator = getBaseUnit().numerator();
    m_denominator = getBaseUnit().denominator();
  }

  @SuppressWarnings("unchecked")
  public static <N extends Unit, D extends Unit> PerUnit<N, D> combine(N numerator, D denominator) {
    return cache.combine(numerator, denominator);
  }
 
  @Override
  @SuppressWarnings("unchecked")
  public PerUnit<N, D> getBaseUnit() {
    return (PerUnit<N, D>) super.getBaseUnit();
  }

  public N numerator() {
    return m_numerator;
  }

  public D denominator() {
    return m_denominator;
  }

  @SuppressWarnings("unchecked")
  public PerUnit<D, N> reciprocal() {
    if (m_numerator instanceof TimeUnit t) {
      // Dividing by time, return a velocity
      return (PerUnit<D, N>) VelocityUnit.combine(m_denominator, t);
    } else {
      // Generic case
      return combine(m_denominator, m_numerator);
    }
  }

  public N mult(D denom) {
    if (denom.equivalent(denominator())) {
      return numerator();
    }
 
    return Units.derive(numerator())
        .toBase(denom.getConverterToBase().div(denominator().getConverterToBase()))
        .fromBase(denom.getConverterFromBase().div(denominator().getConverterFromBase()))
        .named(name() + " " + denom.name())
        .symbol(symbol() + "-" + denom.symbol())
        .make();
  }

  @Override
  public Measure<? extends PerUnit<N, D>> of(double magnitude) {
    return ofNative(magnitude);
  }

  @Override
  public Measure<? extends PerUnit<N, D>> ofBaseUnits(double baseUnitMagnitude) {
    return ofNativeBaseUnits(baseUnitMagnitude);
  }

  public final Per<N, D> ofNative(double magnitude) {
    return new Per<>(magnitude, toBaseUnits(magnitude), this);
  }

  public final Per<N, D> ofNativeBaseUnits(double baseUnitMagnitude) {
    return new Per<>(fromBaseUnits(baseUnitMagnitude), baseUnitMagnitude, this);
  }
 
  @Override
  @SuppressWarnings("unchecked")
  public Measure<? extends PerUnit<N, D>> zero() {
    return (Measure<? extends PerUnit<N, D>>) super.zero();
  }
 
  @Override
  @SuppressWarnings("unchecked")
  public Measure<? extends PerUnit<N, D>> one() {
    return (Measure<? extends PerUnit<N, D>>) super.one();
  }
 
  @Override
  public Unit per(TimeUnit time) {
    return VelocityUnit.combine(this, time);
  }

  public double convertFrom(double magnitude, PerUnit<? extends N, ? extends D> otherUnit) {
    return fromBaseUnits(otherUnit.toBaseUnits(magnitude));
  }
 
  @Override
  public boolean equals(Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    if (!super.equals(o)) {
      return false;
    }
    PerUnit<?, ?> perUnit = (PerUnit<?, ?>) o;
    return Objects.equals(m_numerator, perUnit.m_numerator)
        && Objects.equals(m_denominator, perUnit.m_denominator);
  }
 
  @Override
  public int hashCode() {
    return Objects.hash(super.hashCode(), m_numerator, m_denominator);
  }
}