001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.math3.fraction;
018
019import java.text.FieldPosition;
020import java.text.NumberFormat;
021import java.text.ParsePosition;
022
023import org.apache.commons.math3.exception.util.LocalizedFormats;
024import org.apache.commons.math3.exception.NullArgumentException;
025import org.apache.commons.math3.util.FastMath;
026import org.apache.commons.math3.util.MathUtils;
027
028/**
029 * Formats a Fraction number in proper format.  The number format for each of
030 * the whole number, numerator and, denominator can be configured.
031 * <p>
032 * Minus signs are only allowed in the whole number part - i.e.,
033 * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
034 * will result in a <code>ParseException</code>.</p>
035 *
036 * @since 1.1
037 */
038public class ProperFractionFormat extends FractionFormat {
039
040    /** Serializable version identifier */
041    private static final long serialVersionUID = 760934726031766749L;
042
043    /** The format used for the whole number. */
044    private NumberFormat wholeFormat;
045
046    /**
047     * Create a proper formatting instance with the default number format for
048     * the whole, numerator, and denominator.
049     */
050    public ProperFractionFormat() {
051        this(getDefaultNumberFormat());
052    }
053
054    /**
055     * Create a proper formatting instance with a custom number format for the
056     * whole, numerator, and denominator.
057     * @param format the custom format for the whole, numerator, and
058     *        denominator.
059     */
060    public ProperFractionFormat(NumberFormat format) {
061        this(format, (NumberFormat)format.clone(), (NumberFormat)format.clone());
062    }
063
064    /**
065     * Create a proper formatting instance with a custom number format for each
066     * of the whole, numerator, and denominator.
067     * @param wholeFormat the custom format for the whole.
068     * @param numeratorFormat the custom format for the numerator.
069     * @param denominatorFormat the custom format for the denominator.
070     */
071    public ProperFractionFormat(NumberFormat wholeFormat,
072            NumberFormat numeratorFormat,
073            NumberFormat denominatorFormat)
074    {
075        super(numeratorFormat, denominatorFormat);
076        setWholeFormat(wholeFormat);
077    }
078
079    /**
080     * Formats a {@link Fraction} object to produce a string.  The fraction
081     * is output in proper format.
082     *
083     * @param fraction the object to format.
084     * @param toAppendTo where the text is to be appended
085     * @param pos On input: an alignment field, if desired. On output: the
086     *            offsets of the alignment field
087     * @return the value passed in as toAppendTo.
088     */
089    @Override
090    public StringBuffer format(Fraction fraction, StringBuffer toAppendTo,
091            FieldPosition pos) {
092
093        pos.setBeginIndex(0);
094        pos.setEndIndex(0);
095
096        int num = fraction.getNumerator();
097        int den = fraction.getDenominator();
098        int whole = num / den;
099        num %= den;
100
101        if (whole != 0) {
102            getWholeFormat().format(whole, toAppendTo, pos);
103            toAppendTo.append(' ');
104            num = FastMath.abs(num);
105        }
106        getNumeratorFormat().format(num, toAppendTo, pos);
107        toAppendTo.append(" / ");
108        getDenominatorFormat().format(den, toAppendTo, pos);
109
110        return toAppendTo;
111    }
112
113    /**
114     * Access the whole format.
115     * @return the whole format.
116     */
117    public NumberFormat getWholeFormat() {
118        return wholeFormat;
119    }
120
121    /**
122     * Parses a string to produce a {@link Fraction} object.  This method
123     * expects the string to be formatted as a proper fraction.
124     * <p>
125     * Minus signs are only allowed in the whole number part - i.e.,
126     * "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
127     * will result in a <code>ParseException</code>.</p>
128     *
129     * @param source the string to parse
130     * @param pos input/ouput parsing parameter.
131     * @return the parsed {@link Fraction} object.
132     */
133    @Override
134    public Fraction parse(String source, ParsePosition pos) {
135        // try to parse improper fraction
136        Fraction ret = super.parse(source, pos);
137        if (ret != null) {
138            return ret;
139        }
140
141        int initialIndex = pos.getIndex();
142
143        // parse whitespace
144        parseAndIgnoreWhitespace(source, pos);
145
146        // parse whole
147        Number whole = getWholeFormat().parse(source, pos);
148        if (whole == null) {
149            // invalid integer number
150            // set index back to initial, error index should already be set
151            // character examined.
152            pos.setIndex(initialIndex);
153            return null;
154        }
155
156        // parse whitespace
157        parseAndIgnoreWhitespace(source, pos);
158
159        // parse numerator
160        Number num = getNumeratorFormat().parse(source, pos);
161        if (num == null) {
162            // invalid integer number
163            // set index back to initial, error index should already be set
164            // character examined.
165            pos.setIndex(initialIndex);
166            return null;
167        }
168
169        if (num.intValue() < 0) {
170            // minus signs should be leading, invalid expression
171            pos.setIndex(initialIndex);
172            return null;
173        }
174
175        // parse '/'
176        int startIndex = pos.getIndex();
177        char c = parseNextCharacter(source, pos);
178        switch (c) {
179        case 0 :
180            // no '/'
181            // return num as a fraction
182            return new Fraction(num.intValue(), 1);
183        case '/' :
184            // found '/', continue parsing denominator
185            break;
186        default :
187            // invalid '/'
188            // set index back to initial, error index should be the last
189            // character examined.
190            pos.setIndex(initialIndex);
191            pos.setErrorIndex(startIndex);
192            return null;
193        }
194
195        // parse whitespace
196        parseAndIgnoreWhitespace(source, pos);
197
198        // parse denominator
199        Number den = getDenominatorFormat().parse(source, pos);
200        if (den == null) {
201            // invalid integer number
202            // set index back to initial, error index should already be set
203            // character examined.
204            pos.setIndex(initialIndex);
205            return null;
206        }
207
208        if (den.intValue() < 0) {
209            // minus signs must be leading, invalid
210            pos.setIndex(initialIndex);
211            return null;
212        }
213
214        int w = whole.intValue();
215        int n = num.intValue();
216        int d = den.intValue();
217        return new Fraction(((FastMath.abs(w) * d) + n) * MathUtils.copySign(1, w), d);
218    }
219
220    /**
221     * Modify the whole format.
222     * @param format The new whole format value.
223     * @throws NullArgumentException if {@code format} is {@code null}.
224     */
225    public void setWholeFormat(NumberFormat format) {
226        if (format == null) {
227            throw new NullArgumentException(LocalizedFormats.WHOLE_FORMAT);
228        }
229        this.wholeFormat = format;
230    }
231}