[wpimath] Add direction to slew rate limiter (#4377)

wpimath/src/main/java/edu/wpi/first/math/filter/SlewRateLimiter.java

@@ -14,29 +14,50 @@ import edu.wpi.first.util.WPIUtilJNI;
  * edu.wpi.first.math.trajectory.TrapezoidProfile} instead.
  */
 public class SlewRateLimiter {
-  private final double m_rateLimit;
+  private final double m_positiveRateLimit;
+  private final double m_negativeRateLimit;
   private double m_prevVal;
   private double m_prevTime;
 
   /**
-   * Creates a new SlewRateLimiter with the given rate limit and initial value.
+   * Creates a new SlewRateLimiter with the given positive and negative rate limits and initial
+   * value.
    *
-   * @param rateLimit The rate-of-change limit, in units per second.
+   * @param positiveRateLimit The rate-of-change limit in the positive direction, in units per
+   *     second. This is expected to be positive.
+   * @param negativeRateLimit The rate-of-change limit in the negative direction, in units per
+   *     second. This is expected to be negative.
    * @param initialValue The initial value of the input.
    */
-  public SlewRateLimiter(double rateLimit, double initialValue) {
-    m_rateLimit = rateLimit;
+  public SlewRateLimiter(double positiveRateLimit, double negativeRateLimit, double initialValue) {
+    m_positiveRateLimit = positiveRateLimit;
+    m_negativeRateLimit = negativeRateLimit;
     m_prevVal = initialValue;
     m_prevTime = WPIUtilJNI.now() * 1e-6;
   }
 
   /**
-   * Creates a new SlewRateLimiter with the given rate limit and an initial value of zero.
+   * Creates a new SlewRateLimiter with the given positive rate limit and negative rate limit of
+   * -rateLimit and initial value.
+   *
+   * @param rateLimit The rate-of-change limit, in units per second.
+   * @param initalValue The initial value of the input.
+   * @deprecated Use SlewRateLimiter(double positiveRateLimit, double negativeRateLimit, double
+   *     initalValue) instead.
+   */
+  @Deprecated(since = "2023", forRemoval = true)
+  public SlewRateLimiter(double rateLimit, double initalValue) {
+    this(rateLimit, -rateLimit, initalValue);
+  }
+
+  /**
+   * Creates a new SlewRateLimiter with the given positive rate limit and negative rate limit of
+   * -rateLimit.
    *
    * @param rateLimit The rate-of-change limit, in units per second.
    */
   public SlewRateLimiter(double rateLimit) {
-    this(rateLimit, 0);
+    this(rateLimit, -rateLimit, 0);
   }
 
   /**
@@ -49,7 +70,10 @@ public class SlewRateLimiter {
     double currentTime = WPIUtilJNI.now() * 1e-6;
     double elapsedTime = currentTime - m_prevTime;
     m_prevVal +=
-        MathUtil.clamp(input - m_prevVal, -m_rateLimit * elapsedTime, m_rateLimit * elapsedTime);
+        MathUtil.clamp(
+            input - m_prevVal,
+            m_negativeRateLimit * elapsedTime,
+            m_positiveRateLimit * elapsedTime);
     m_prevTime = currentTime;
     return m_prevVal;
   }