/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.linear;

import org.apache.commons.math.Field;
import org.apache.commons.math.FieldElement;

/**
 * Interface defining a field-valued vector with basic algebraic operations.
 * <p>
 * vector element indexing is 0-based -- e.g., <code>getEntry(0)</code> returns
 * the first element of the vector.
 * </p>
 * <p>
 * The various <code>mapXxx</code> and <code>mapXxxToSelf</code> methods operate
 * on vectors element-wise, i.e. they perform the same operation (adding a
 * scalar, applying a function ...) on each element in turn. The
 * <code>mapXxx</code> versions create a new vector to hold the result and do
 * not change the instance. The <code>mapXxxToSelf</code> versions use the
 * instance itself to store the results, so the instance is changed by these
 * methods. In both cases, the result vector is returned by the methods, this
 * allows to use the <i>fluent API</i> style, like this:
 * </p>
 * 
 * <pre>
 * RealVector result = v.mapAddToSelf(3.0).mapTanToSelf().mapSquareToSelf();
 * </pre>
 * 
 * @param <T>
 *            the type of the field elements
 * @version $Revision$ $Date$
 * @since 2.0
 */
public interface FieldVector<T extends FieldElement<T>> {

	/**
	 * Get the type of field elements of the vector.
	 * 
	 * @return type of field elements of the vector
	 */
	Field<T> getField();

	/**
	 * Returns a (deep) copy of this.
	 * 
	 * @return vector copy
	 */
	FieldVector<T> copy();

	/**
	 * Compute the sum of this and v.
	 * 
	 * @param v
	 *            vector to be added
	 * @return this + v
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	FieldVector<T> add(FieldVector<T> v) throws IllegalArgumentException;

	/**
	 * Compute the sum of this and v.
	 * 
	 * @param v
	 *            vector to be added
	 * @return this + v
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	FieldVector<T> add(T[] v) throws IllegalArgumentException;

	/**
	 * Compute this minus v.
	 * 
	 * @param v
	 *            vector to be subtracted
	 * @return this + v
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	FieldVector<T> subtract(FieldVector<T> v) throws IllegalArgumentException;

	/**
	 * Compute this minus v.
	 * 
	 * @param v
	 *            vector to be subtracted
	 * @return this + v
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	FieldVector<T> subtract(T[] v) throws IllegalArgumentException;

	/**
	 * Map an addition operation to each entry.
	 * 
	 * @param d
	 *            value to be added to each entry
	 * @return this + d
	 */
	FieldVector<T> mapAdd(T d);

	/**
	 * Map an addition operation to each entry.
	 * <p>
	 * The instance <strong>is</strong> changed by this method.
	 * </p>
	 * 
	 * @param d
	 *            value to be added to each entry
	 * @return for convenience, return this
	 */
	FieldVector<T> mapAddToSelf(T d);

	/**
	 * Map a subtraction operation to each entry.
	 * 
	 * @param d
	 *            value to be subtracted to each entry
	 * @return this - d
	 */
	FieldVector<T> mapSubtract(T d);

	/**
	 * Map a subtraction operation to each entry.
	 * <p>
	 * The instance <strong>is</strong> changed by this method.
	 * </p>
	 * 
	 * @param d
	 *            value to be subtracted to each entry
	 * @return for convenience, return this
	 */
	FieldVector<T> mapSubtractToSelf(T d);

	/**
	 * Map a multiplication operation to each entry.
	 * 
	 * @param d
	 *            value to multiply all entries by
	 * @return this * d
	 */
	FieldVector<T> mapMultiply(T d);

	/**
	 * Map a multiplication operation to each entry.
	 * <p>
	 * The instance <strong>is</strong> changed by this method.
	 * </p>
	 * 
	 * @param d
	 *            value to multiply all entries by
	 * @return for convenience, return this
	 */
	FieldVector<T> mapMultiplyToSelf(T d);

	/**
	 * Map a division operation to each entry.
	 * 
	 * @param d
	 *            value to divide all entries by
	 * @return this / d
	 */
	FieldVector<T> mapDivide(T d);

	/**
	 * Map a division operation to each entry.
	 * <p>
	 * The instance <strong>is</strong> changed by this method.
	 * </p>
	 * 
	 * @param d
	 *            value to divide all entries by
	 * @return for convenience, return this
	 */
	FieldVector<T> mapDivideToSelf(T d);

	/**
	 * Map the 1/x function to each entry.
	 * 
	 * @return a vector containing the result of applying the function to each
	 *         entry
	 */
	FieldVector<T> mapInv();

	/**
	 * Map the 1/x function to each entry.
	 * <p>
	 * The instance <strong>is</strong> changed by this method.
	 * </p>
	 * 
	 * @return for convenience, return this
	 */
	FieldVector<T> mapInvToSelf();

	/**
	 * Element-by-element multiplication.
	 * 
	 * @param v
	 *            vector by which instance elements must be multiplied
	 * @return a vector containing this[i] * v[i] for all i
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	public FieldVector<T> ebeMultiply(FieldVector<T> v) throws IllegalArgumentException;

	/**
	 * Element-by-element multiplication.
	 * 
	 * @param v
	 *            vector by which instance elements must be multiplied
	 * @return a vector containing this[i] * v[i] for all i
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	public FieldVector<T> ebeMultiply(T[] v) throws IllegalArgumentException;

	/**
	 * Element-by-element division.
	 * 
	 * @param v
	 *            vector by which instance elements must be divided
	 * @return a vector containing this[i] / v[i] for all i
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	public FieldVector<T> ebeDivide(FieldVector<T> v) throws IllegalArgumentException;

	/**
	 * Element-by-element division.
	 * 
	 * @param v
	 *            vector by which instance elements must be divided
	 * @return a vector containing this[i] / v[i] for all i
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	public FieldVector<T> ebeDivide(T[] v) throws IllegalArgumentException;

	/**
	 * Returns vector entries as a T array.
	 * 
	 * @return T array of entries
	 */
	T[] getData();

	/**
	 * Compute the dot product.
	 * 
	 * @param v
	 *            vector with which dot product should be computed
	 * @return the scalar dot product between instance and v
	 * @exception IllegalArgumentException
	 *                if v is not the same size as this
	 */
	T dotProduct(FieldVector<T> v) throws IllegalArgumentException;

	/**
	 * Compute the dot product.
	 * 
	 * @param v
	 *            vector with which dot product should be computed
	 * @return the scalar dot product between instance and v
	 * @exception IllegalArgumentException
	 *                if v is not the same size as this
	 */
	T dotProduct(T[] v) throws IllegalArgumentException;

	/**
	 * Find the orthogonal projection of this vector onto another vector.
	 * 
	 * @param v
	 *            vector onto which instance must be projected
	 * @return projection of the instance onto v
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	FieldVector<T> projection(FieldVector<T> v) throws IllegalArgumentException;

	/**
	 * Find the orthogonal projection of this vector onto another vector.
	 * 
	 * @param v
	 *            vector onto which instance must be projected
	 * @return projection of the instance onto v
	 * @throws IllegalArgumentException
	 *             if v is not the same size as this
	 */
	FieldVector<T> projection(T[] v) throws IllegalArgumentException;

	/**
	 * Compute the outer product.
	 * 
	 * @param v
	 *            vector with which outer product should be computed
	 * @return the square matrix outer product between instance and v
	 * @exception IllegalArgumentException
	 *                if v is not the same size as this
	 */
	FieldMatrix<T> outerProduct(FieldVector<T> v) throws IllegalArgumentException;

	/**
	 * Compute the outer product.
	 * 
	 * @param v
	 *            vector with which outer product should be computed
	 * @return the square matrix outer product between instance and v
	 * @exception IllegalArgumentException
	 *                if v is not the same size as this
	 */
	FieldMatrix<T> outerProduct(T[] v) throws IllegalArgumentException;

	/**
	 * Returns the entry in the specified index.
	 * <p>
	 * The index start at 0 and must be lesser than the size, otherwise a
	 * {@link MatrixIndexException} is thrown.
	 * </p>
	 * 
	 * @param index
	 *            index location of entry to be fetched
	 * @return vector entry at index
	 * @throws MatrixIndexException
	 *             if the index is not valid
	 * @see #setEntry(int, FieldElement)
	 */
	T getEntry(int index) throws MatrixIndexException;

	/**
	 * Set a single element.
	 * 
	 * @param index
	 *            element index.
	 * @param value
	 *            new value for the element.
	 * @exception MatrixIndexException
	 *                if the index is inconsistent with vector size
	 * @see #getEntry(int)
	 */
	void setEntry(int index, T value) throws MatrixIndexException;

	/**
	 * Returns the size of the vector.
	 * 
	 * @return size
	 */
	int getDimension();

	/**
	 * Construct a vector by appending a vector to this vector.
	 * 
	 * @param v
	 *            vector to append to this one.
	 * @return a new vector
	 */
	FieldVector<T> append(FieldVector<T> v);

	/**
	 * Construct a vector by appending a T to this vector.
	 * 
	 * @param d
	 *            T to append.
	 * @return a new vector
	 */
	FieldVector<T> append(T d);

	/**
	 * Construct a vector by appending a T array to this vector.
	 * 
	 * @param a
	 *            T array to append.
	 * @return a new vector
	 */
	FieldVector<T> append(T[] a);

	/**
	 * Get a subvector from consecutive elements.
	 * 
	 * @param index
	 *            index of first element.
	 * @param n
	 *            number of elements to be retrieved.
	 * @return a vector containing n elements.
	 * @exception MatrixIndexException
	 *                if the index is inconsistent with vector size
	 */
	FieldVector<T> getSubVector(int index, int n) throws MatrixIndexException;

	/**
	 * Set a set of consecutive elements.
	 * 
	 * @param index
	 *            index of first element to be set.
	 * @param v
	 *            vector containing the values to set.
	 * @exception MatrixIndexException
	 *                if the index is inconsistent with vector size
	 * @see #setSubVector(int, FieldElement[])
	 */
	void setSubVector(int index, FieldVector<T> v) throws MatrixIndexException;

	/**
	 * Set a set of consecutive elements.
	 * 
	 * @param index
	 *            index of first element to be set.
	 * @param v
	 *            vector containing the values to set.
	 * @exception MatrixIndexException
	 *                if the index is inconsistent with vector size
	 * @see #setSubVector(int, FieldVector)
	 */
	void setSubVector(int index, T[] v) throws MatrixIndexException;

	/**
	 * Set all elements to a single value.
	 * 
	 * @param value
	 *            single value to set for all elements
	 */
	void set(T value);

	/**
	 * Convert the vector to a T array.
	 * <p>
	 * The array is independent from vector data, it's elements are copied.
	 * </p>
	 * 
	 * @return array containing a copy of vector elements
	 */
	T[] toArray();

}
