org.antlr.v4.runtime.misc.Interval Maven / Gradle / Ivy
/*
* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
package org.antlr.v4.runtime.misc;
/** An immutable inclusive interval a..b */
public class Interval {
public static final int INTERVAL_POOL_MAX_VALUE = 1000;
public static final Interval INVALID = new Interval(-1,-2);
static final Interval[] cache = new Interval[INTERVAL_POOL_MAX_VALUE+1];
public int a;
public int b;
public Interval(int a, int b) { this.a=a; this.b=b; }
/** Interval objects are used readonly so share all with the
* same single value a==b up to some max size. Use an array as a perfect hash.
* Return shared object for 0..INTERVAL_POOL_MAX_VALUE or a new
* Interval object with a..a in it. On Java.g4, 218623 IntervalSets
* have a..a (set with 1 element).
*/
public static Interval of(int a, int b) {
// cache just a..a
if ( a!=b || a<0 || a>INTERVAL_POOL_MAX_VALUE ) {
return new Interval(a,b);
}
if ( cache[a]==null ) {
cache[a] = new Interval(a,a);
}
return cache[a];
}
/** return number of elements between a and b inclusively. x..x is length 1.
* if b < a, then length is 0. 9..10 has length 2.
*/
public int length() {
if ( b=other.a;
}
/** Does this.a start after other.b? May or may not be disjoint */
public boolean startsAfter(Interval other) { return this.a>other.a; }
/** Does this start completely after other? Disjoint */
public boolean startsAfterDisjoint(Interval other) {
return this.a>other.b;
}
/** Does this start after other? NonDisjoint */
public boolean startsAfterNonDisjoint(Interval other) {
return this.a>other.a && this.a<=other.b; // this.b>=other.b implied
}
/** Are both ranges disjoint? I.e., no overlap? */
public boolean disjoint(Interval other) {
return startsBeforeDisjoint(other) || startsAfterDisjoint(other);
}
/** Are two intervals adjacent such as 0..41 and 42..42? */
public boolean adjacent(Interval other) {
return this.a == other.b+1 || this.b == other.a-1;
}
public boolean properlyContains(Interval other) {
return other.a >= this.a && other.b <= this.b;
}
/** Return the interval computed from combining this and other */
public Interval union(Interval other) {
return Interval.of(Math.min(a, other.a), Math.max(b, other.b));
}
/** Return the interval in common between this and o */
public Interval intersection(Interval other) {
return Interval.of(Math.max(a, other.a), Math.min(b, other.b));
}
/** Return the interval with elements from this not in other;
* other must not be totally enclosed (properly contained)
* within this, which would result in two disjoint intervals
* instead of the single one returned by this method.
*/
public Interval differenceNotProperlyContained(Interval other) {
Interval diff = null;
// other.a to left of this.a (or same)
if ( other.startsBeforeNonDisjoint(this) ) {
diff = Interval.of(Math.max(this.a, other.b + 1),
this.b);
}
// other.a to right of this.a
else if ( other.startsAfterNonDisjoint(this) ) {
diff = Interval.of(this.a, other.a - 1);
}
return diff;
}
@Override
public String toString() {
return a+".."+b;
}
}