# Entity¶

public abstract class Entity<T>

An AMPL entity such as a parameter or a variable. An entity can either represent a single instance of an AMPL algebraic entity or, if the corresponding declaration has an indexing expression, a mapping from keys to instances. In the derived classes, it has methods to access instance-level properties which can be used in case the represented entity is scalar. To gain access to all the values in an entity (for all instances and all suffixes for that entities), use getValues.

## Fields¶

### ARE_DEPENDENCIES_VALID¶

static final int ARE_DEPENDENCIES_VALID

Flag that specifies whether the entity’s dependencies might have changed (so far just through normal “interpret”)

### ENTITY_DELETED¶

static final int ENTITY_DELETED

Flag that specifies whether the entity has been deleted (is invalid)

### IS_VALID¶

static final int IS_VALID

Flag that specifies whether the entity contains valid (up to date) data. Initialization is performed lazily when the entity is first accessed except when it is done through the data statements.

### NO_DATA¶

static final int NO_DATA

Flag that specifies whether the entity doesn’t contain any data.

### ampl¶

AMPL ampl

### declaration¶

String declaration

### engine¶

Engine engine

### map¶

Map<Object, T> map

Key can be Double, String or Tuple. If this entity represents a single object, the entity contains at most one item and the key is null.

### name¶

String name

### type¶

EntityType type_

## Constructors¶

### Entity¶

Entity()

Constructor

### Entity¶

Entity(AMPL ampl, Engine engine, String name, EntityType type)

Constructor

Parameters: ampl – AMPL instance engine – Engine instance name – Entity’s name

## Methods¶

final void addDependent(Entity<?> dep)

### areDependenciesUpdated¶

final boolean areDependenciesUpdated()

### checkDimensionOfKey¶

boolean checkDimensionOfKey(Object t)

### checkForDeletion¶

boolean checkForDeletion()

### checkHasIndexing¶

void checkHasIndexing()

### clearNoData¶

final void clearNoData()

Clear the nodata flag

### displayEmbedded¶

String displayEmbedded()

Display the value(s) of the entity, using the embedded display routine

Returns: String visualization

### entrySet¶

public Set<Map.Entry<Object, T>> entrySet()

Get a set view of this entity. Each entry in the set contains the key (value of the indices) and the corresponding instance. For a scalar entity, a set with just one entry is returned, which has a null key and the only instance as value.

The following example prints indices and values of the variable Buy indexed over the set FOOD (taken from the diet model):

for(Map.Entry<Object, VariableInstance> e: ampl.getVariable("Buy").entrySet()) {
Object food = e.getKey();
}

Returns: An unmodifiable set containing all the entries of this entity.

### executeAMPLStatement¶

boolean executeAMPLStatement(String statement)

### fromMatlab¶

Object[] fromMatlab(double[] indices)

### fromMatlab¶

<J> Object[] fromMatlab(J[] indices)

### get¶

public abstract T get()

Get the instance corresponding to a scalar entity.

Throws: UnsupportedOperationException – if the entity is not scalar. IllegalStateException – if the entity has been deleted in the underlying AMPL interpreter The corresponding instance.

### get¶

public abstract T get(Object... key)

Get the instance corresponding to the specified key. See Access to instances and values for further information on how the key can be specified.

Parameters: key – Key of the instance to be found. IllegalArgumentException – if trying to access an instance with the wrong number of keys (see Entity.indexarity) IllegalStateException – if the entity has been deleted in the underlying AMPL interpreter The instance corresponding to the key, or null if the specified key is not found.

### get¶

public abstract T get(Tuple key)

Get the instance corresponding to the specified tuple. See Access to instances and values for further information on how the key can be specified.

Parameters: key – Key (in form of Tuple) of the instance to be found. IllegalArgumentException – if trying to access an instance with the wrong number of keys (see Entity.indexarity) IllegalStateException – if the entity has been deleted in the underlying AMPL interpreter The instance corresponding to the key, or null if the specified key is not found.

### getAsDoubles¶

double[] getAsDoubles()

Get value of all the instances in the current entity as doubles. Returns default suffixes: value for variables and objectives, body for constraints and the value of parameters. Casts the members of sets to doubles.

Throws: NumberFormatException – If the content of the entity cannot be represented by double numbers Array of double numbers

### getAsDoubles¶

double[] getAsDoubles(String suffix)

Get specific suffixes of the current entity as doubles

Parameters: suffix – The specific suffix to return Array of double numbers

### getAsObjects¶

Object[] getAsObjects(String suffix)

Get specific suffixes of the current entity as objects

Parameters: suffix – The specific suffix to return Array of double numbers

### getDeclaration¶

String getDeclaration()

Get the declaration of the AMPL entity represented by this Entity.

Returns: AMPL declaration of this entity.

### getDependents¶

ArrayList<Entity<?>> getDependents()

### getIndexingDummies¶

String getIndexingDummies()

### getIndexingSets¶

public String[] getIndexingSets()

Get the AMPL string representation of the sets on which this entity is indexed.

Returns: The string representation of the indexing sets for this entity or an empty array if the entity is scalar

### getIndices¶

public Set<Object> getIndices()

Get all the keys in this entity. Not modifiable as a collection.

Returns: All the keys currently in the entity.

### getInstances¶

public Collection<T> getInstances()

Get all instances in this entity. Not modifiable as a collection

Returns: All instances currently generated for this entity.

### getMethod¶

T getMethod(Object... key)

### getMethod¶

T getMethod(Tuple key)

### getValues¶

public DataFrame getValues()

Get the principal values of this entity as a DataFrame. For variables and objectives it returns their suffix val for parameters it returns their values for constraints it returns the suffix dual for sets it returns all the members of the set

Returns: All instances

### getValues¶

public DataFrame getValues(String... suffixes)

Get all the specified values for this entity as a DataFrame object. The valid strings are all AMPL built-in suffixes for the entity under consideration.

Parameters: suffixes – A list of suffixes to be returned IllegalArgumentException – if the specified suffix does not exist. A DataFrame object with a column for each indexing set and a column for each one of the specified suffixes.

### hasData¶

boolean hasData()

### hasIndexing¶

public boolean hasIndexing()

Check whether this entity is indexed over any set. Equivalent to testing whether Entity.indexarity is greater than zero.

Returns: True if the entity is not scalar (is indexed over a set)

### hasIndexingInstances¶

boolean hasIndexingInstances()

### indexarity¶

public int indexarity()

Get the indexarity of this entity (sum of the dimensions of the indexing sets). This value indicates how many elements are to be passed to the method Entity.get in order to access an instance of this entity.

See the following AMPL examples:

var x;               # indexarity = 0
var y {1..2};        # indexarity = 1
var z {1..2,3..4};   # indexarity = 2
var zz {{(1, 2)}};   # indexarity = 2

Returns: The sum of the dimensions of the indexing sets or 0 if the entity is not indexed

### invalidate¶

void invalidate()

### invalidateDependencies¶

void invalidateDependencies()

### invalidateDependents¶

void invalidateDependents()

### isDeleted¶

final boolean isDeleted()

### isScalar¶

public boolean isScalar()

Check whether this entity is scalar. Equivalent to testing whether Entity.indexarity is equal to zero.

Returns: True if the entity is scalar (not indexed over any set)

### isValid¶

final boolean isValid()

### name¶

public final String name()

Get the AMPL name of this entity

### numInstances¶

public int numInstances()

Get the number of instances in this entity

### onDelete¶

final void onDelete()

### printArguments¶

void printArguments(Object o)

### refreshDeclaration¶

boolean refreshDeclaration()

Refresh the declaration (and sets) of this entity

### refreshInstances¶

abstract void refreshInstances()

### setDeclaration¶

abstract void setDeclaration(String declaration)

### setIndexArity¶

void setIndexArity(int indexarity)

### setName¶

final void setName(String name)

### setNoData¶

final void setNoData()

### setSets¶

void setSets(String[] sets)

### setValues¶

public void setValues(DataFrame data)

Set the values of this entiy to the correponding values of a DataFrame indexed over the same sets (or a subset). This function assigns the values in the first data column of the passed dataframe to the entity the function is called from. In particular, the statement:: x.setValues(y.getValues()); is semantically equivalent to the AMPL statement:: let {s in S} x[s] := y[s]; *

Parameters: data –

### setnewInstances¶

void setnewInstances(Instance<?>[] newinstances)

### toString¶

public String toString()

Get a string representation of this entity; for all entity types, it returns the AMPL declaration.

### transformKey¶

Object transformKey(Object... key)

### update¶

final void update()

Updates the entity if necessary by refreshing the instances

### updateDependenciesFlag¶

void updateDependenciesFlag()

SetInstance dependencies valid flag

### validate¶

void validate()

Flag this entity to valid

### xref¶

public List<Entity<?>> xref()

Get all the entities which depend on this one