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dafny.DafnyMultiset Maven / Gradle / Ivy
// Copyright by the contributors to the Dafny Project
// SPDX-License-Identifier: MIT
package dafny;
import java.math.BigInteger;
import java.util.*;
public class DafnyMultiset {
/*
Invariant: forall x. m.get(x) == null || m.get(x) > 0
As in Java, null is allowed as a key
*/
private Map innerMap;
public DafnyMultiset() {
innerMap = new HashMap<>();
}
// Requires that all values in m are non-negative
public DafnyMultiset(Map m) {
assert m != null : "Precondition Violation";
innerMap = new HashMap<>();
for (Map.Entry e : m.entrySet()) {
BigInteger n = e.getValue();
int cmp = n.compareTo(BigInteger.ZERO);
assert 0 <= cmp : "Precondition Violation";
if (0 < cmp) {
innerMap.put(e.getKey(), n);
}
}
}
public DafnyMultiset(Set s) {
assert s != null : "Precondition Violation";
innerMap = new HashMap<>();
for (T t : s) {
incrementMultiplicity(t, BigInteger.ONE);
}
}
public DafnyMultiset(Collection c) {
assert c != null : "Precondition Violation";
innerMap = new HashMap<>();
for (T t : c) {
incrementMultiplicity(t, BigInteger.ONE);
}
}
// Adds all elements found in the list to a new DafnyMultiSet. The number of occurrences in the list becomes the
// multiplicity in the DafnyMultiset
public DafnyMultiset(List l) {
assert l != null : "Precondition Violation";
innerMap = new HashMap<>();
for (T t : l) {
incrementMultiplicity(t, BigInteger.ONE);
}
}
@SafeVarargs
public static DafnyMultiset of(T ... args) {
return new DafnyMultiset(Arrays.asList(args));
}
private static final DafnyMultiset EMPTY = DafnyMultiset.of();
@SuppressWarnings("unchecked")
public static DafnyMultiset empty() {
// Safe because immutable
return (DafnyMultiset) EMPTY;
}
@SuppressWarnings("unchecked")
public static TypeDescriptor> _typeDescriptor(TypeDescriptor elementType) {
// Fudge the type parameter; it's not great, but it's safe because
// (for now) type descriptors are only used for default values
return TypeDescriptor.referenceWithDefault(
(Class>) (Class) DafnyMultiset.class,
DafnyMultiset.empty());
}
public BigInteger cardinality() {
BigInteger sum = BigInteger.ZERO;
for (BigInteger m : innerMap.values()) {
sum = sum.add(m);
}
return sum;
}
// cardinalityInt should be called only if the cardinality is known to fit in an "int"
public int cardinalityInt() {
int sum = 0;
for (BigInteger m : innerMap.values()) {
sum += m.intValue();
}
return sum;
}
// Determines if the current object is a subset of the DafnyMultiSet passed in. Requires that the input
// DafnyMultiset is not null.
@SuppressWarnings("unchecked")
public boolean isSubsetOf(DafnyMultiset other) {
assert other != null : "Precondition Violation";
for (Map.Entry entry : innerMap.entrySet()) {
if (multiplicity(other, entry.getKey()).compareTo(entry.getValue()) < 0) return false;
}
return true;
}
// Determines if the current object is a proper subset of the DafnyMultiSet passed in. Requires that the input
// Dafny MultiSet is not null.
public boolean isProperSubsetOf(DafnyMultiset other) {
assert other != null : "Precondition Violation";
return isSubsetOf(other) && this.cardinality().compareTo(other.cardinality()) < 0;
}
public boolean contains(Object t) {
// Relies on invariant that all keys have a positive multiplicity
return innerMap.containsKey(t);
}
public boolean disjoint(DafnyMultiset other) {
assert other != null : "Precondition Violation";
for (U u : other.innerMap.keySet()) {
if (innerMap.containsKey(u)) return false;
}
return true;
}
@SuppressWarnings("unchecked")
public static BigInteger multiplicity(DafnyMultiset th, T t) {
BigInteger m = th.innerMap.get(t);
return m == null ? BigInteger.ZERO : m;
}
@SuppressWarnings("unchecked")
public static DafnyMultiset update(DafnyMultiset th, T t, BigInteger b) {
assert th != null : "Precondition Violation";
assert b != null && b.compareTo(BigInteger.ZERO) >= 0 : "Precondition Violation";
DafnyMultiset copy = new DafnyMultiset<>(((DafnyMultiset)th).innerMap);
copy.setMultiplicity(t, b);
return copy;
}
// destructively sets multiplicity of t to b; a negative value is treated as 0
private void setMultiplicity(T t, BigInteger b) {
assert b != null : "Precondition Violation";
if (b.compareTo(BigInteger.ZERO) > 0) {
innerMap.put(t, b);
} else {
innerMap.remove(t);
}
}
// destructively adds n (possibly negative) to value of t
private void incrementMultiplicity(T t, BigInteger b) {
assert b != null : "Precondition Violation";
setMultiplicity(t, multiplicity(this, t).add(b));
}
@SuppressWarnings("unchecked")
public static DafnyMultiset union(DafnyMultiset th, DafnyMultiset other) {
assert th != null : "Precondition Violation";
assert other != null : "Precondition Violation";
DafnyMultiset u = new DafnyMultiset<>(((DafnyMultiset)th).innerMap);
for (Map.Entry entry : ((DafnyMultiset)other).innerMap.entrySet()) {
u.incrementMultiplicity(entry.getKey(), entry.getValue());
}
return u;
}
// Returns a DafnyMultiSet with multiplicities that are
// max(this.multiplicity(e)-other.multiplicity(e), BigInteger.ZERO)
@SuppressWarnings("unchecked")
public static DafnyMultiset difference(DafnyMultiset th, DafnyMultiset other) {
assert th != null : "Precondition Violation";
assert other != null : "Precondition Violation";
DafnyMultiset u = new DafnyMultiset<>(((DafnyMultiset)th).innerMap);
for (Map.Entry entry : ((DafnyMultiset)other).innerMap.entrySet()) {
T key = entry.getKey();
BigInteger m0 = multiplicity(u, key);
BigInteger m1 = entry.getValue();
u.setMultiplicity(key, m0.subtract(m1));
}
return u;
}
// Returns a DafnyMultiSet with multiplicities that are min(this.multiplicity(e), other.multiplicity(e))
@SuppressWarnings("unchecked")
public static DafnyMultiset intersection(DafnyMultiset th, DafnyMultiset other) {
assert th != null : "Precondition Violation";
assert other != null : "Precondition Violation";
DafnyMultiset u = new DafnyMultiset<>();
for (Map.Entry entry : ((DafnyMultiset)th).innerMap.entrySet()) {
T key = entry.getKey();
BigInteger m0 = entry.getValue();
BigInteger m1 = multiplicity((DafnyMultiset)other, key);
u.setMultiplicity(key, m0.min(m1));
}
return u;
}
public Iterable Elements(){
ArrayList r = new ArrayList<>();
for(Map.Entry e : innerMap.entrySet()){
for(int i = 0; i < e.getValue().intValue(); i++){
r.add(e.getKey());
}
}
return r;
}
public Iterable UniqueElements(){
return innerMap.keySet();
}
@Override
protected Object clone() throws CloneNotSupportedException {
return super.clone();
}
@Override
@SuppressWarnings("UNCHECKED_CAST")
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
DafnyMultiset o = (DafnyMultiset) obj;
return innerMap.equals(o.innerMap);
}
@Override
public int hashCode() {
return innerMap.hashCode();
}
@Override
public String toString() {
String s = "multiset{";
String sep = "";
for (Map.Entry entry : innerMap.entrySet()) {
String t = Helpers.toString(entry.getKey());
BigInteger n = entry.getValue();
for (BigInteger i = BigInteger.ZERO; i.compareTo(n) < 0; i = i.add(BigInteger.ONE)) {
s += sep + t;
sep = ", ";
}
}
return s + "}";
}
}
