Imaginary.java
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package org.apache.poi.ss.formula.functions;
import org.apache.poi.ss.formula.OperationEvaluationContext;
import org.apache.poi.ss.formula.eval.*;
import java.util.regex.Pattern;
/**
* Implementation for Excel IMAGINARY() function.
* <p>
* <b>Syntax</b>:<br> <b>IMAGINARY </b>(<b>Inumber</b>)<br>
* <p>
* Returns the imaginary coefficient of a complex number in x + yi or x + yj text format.
* <p>
* Inumber is a complex number for which you want the imaginary coefficient.
* <p>
* Remarks
* <ul>
* <li>Use COMPLEX to convert real and imaginary coefficients into a complex number.</li>
* </ul>
*/
public class Imaginary extends Fixed1ArgFunction implements FreeRefFunction {
public static final FreeRefFunction instance = new Imaginary();
public static final String GROUP1_REAL_SIGN_REGEX = "([+-]?)";
public static final String GROUP2_REAL_INTEGER_OR_DOUBLE_REGEX = "([0-9]+\\.[0-9]+|[0-9]*)";
public static final String GROUP3_IMAGINARY_SIGN_REGEX = "([+-]?)";
public static final String GROUP4_IMAGINARY_INTEGER_OR_DOUBLE_REGEX = "([0-9]+\\.[0-9]+|[0-9]*)";
public static final String GROUP5_IMAGINARY_GROUP_REGEX = "([ij]?)";
public static final Pattern COMPLEX_NUMBER_PATTERN
= Pattern.compile(GROUP1_REAL_SIGN_REGEX + GROUP2_REAL_INTEGER_OR_DOUBLE_REGEX +
GROUP3_IMAGINARY_SIGN_REGEX + GROUP4_IMAGINARY_INTEGER_OR_DOUBLE_REGEX + GROUP5_IMAGINARY_GROUP_REGEX);
public static final int GROUP1_REAL_SIGN = 1;
public static final int GROUP2_IMAGINARY_INTEGER_OR_DOUBLE = 2;
public static final int GROUP3_IMAGINARY_SIGN = 3;
public static final int GROUP4_IMAGINARY_INTEGER_OR_DOUBLE = 4;
@Override
public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval inumberVE) {
ValueEval veText1;
try {
veText1 = OperandResolver.getSingleValue(inumberVE, srcRowIndex, srcColumnIndex);
} catch (EvaluationException e) {
return e.getErrorEval();
}
String iNumber = OperandResolver.coerceValueToString(veText1);
String[] groups = parseComplexNumber(iNumber);
String imaginary = "";
if (groups != null) {
String imaginaryGroup = groups[5];
boolean hasImaginaryPart = imaginaryGroup.equals("i") || imaginaryGroup.equals("j");
if (imaginaryGroup.isEmpty()) {
return new StringEval(String.valueOf(0));
}
if (hasImaginaryPart) {
String sign = "";
String imaginarySign = groups[GROUP3_IMAGINARY_SIGN];
String groupImaginaryNumber = groups[GROUP4_IMAGINARY_INTEGER_OR_DOUBLE];
if (isImaginaryOnly(groups)) {
// e.g. "-i" or "3i": the sign and coefficient were matched as the real part
imaginarySign = groups[GROUP1_REAL_SIGN];
groupImaginaryNumber = groups[GROUP2_IMAGINARY_INTEGER_OR_DOUBLE];
}
if (imaginarySign.length() != 0 && !(imaginarySign.equals("+"))) {
sign = imaginarySign;
}
if (groupImaginaryNumber.length() != 0) {
imaginary = sign + groupImaginaryNumber;
} else {
imaginary = sign + "1";
}
}
} else {
return ErrorEval.NUM_ERROR;
}
return new StringEval(imaginary);
}
/**
* Whether the groups from {@link #parseComplexNumber(String)} are a number without a real part, e.g. "-i" or "3i".
* The pattern then captures the sign and coefficient in the real part groups, and the imaginary ones are empty.
*/
static boolean isImaginaryOnly(String[] groups) {
return !groups[5].isEmpty() && groups[GROUP3_IMAGINARY_SIGN].isEmpty()
&& groups[GROUP4_IMAGINARY_INTEGER_OR_DOUBLE].isEmpty();
}
/**
* Gives the same result as matching {@link #COMPLEX_NUMBER_PATTERN}, without the regular expression:
* its groups can split a run of digits in many ways, so matching text that is not a complex number
* took polynomial time. This tries the same splits in the same order as the regular expression
* backtracking does, but checks each one in constant time.
*
* @return the groups that {@link java.util.regex.Matcher#group(int)} would return, indexed by group number
* (index 0 is the whole text), or {@code null} if the text does not match the pattern
*/
static String[] parseComplexNumber(String text) {
int n = text.length();
// digitsEnd[i] is the end of the run of digits that starts at i
int[] digitsEnd = new int[n + 1];
digitsEnd[n] = n;
for (int i = n - 1; i >= 0; i--) {
digitsEnd[i] = isDigit(text.charAt(i)) ? digitsEnd[i + 1] : i;
}
// group 1: [+-]? tries the sign first
boolean hasRealSign = n > 0 && isSign(text.charAt(0));
for (int realStart = hasRealSign ? 1 : 0; realStart >= 0; realStart--) {
// group 2: [0-9]+\.[0-9]+ with fewer and fewer digits after the '.', then [0-9]* with fewer and fewer digits
int pointEnd = decimalPointEnd(text, realStart, digitsEnd);
if (pointEnd >= 0) {
for (int realEnd = digitsEnd[pointEnd]; realEnd > pointEnd; realEnd--) {
String[] groups = parseImaginaryPart(text, realStart, realEnd, digitsEnd);
if (groups != null) {
return groups;
}
}
}
for (int realEnd = digitsEnd[realStart]; realEnd >= realStart; realEnd--) {
String[] groups = parseImaginaryPart(text, realStart, realEnd, digitsEnd);
if (groups != null) {
return groups;
}
}
}
return null;
}
/** groups 3 to 5, for groups 1 and 2 ending at {@code realStart} and {@code realEnd} */
private static String[] parseImaginaryPart(String text, int realStart, int realEnd, int[] digitsEnd) {
int n = text.length();
// group 3: [+-]? tries the sign first
boolean hasImaginarySign = realEnd < n && isSign(text.charAt(realEnd));
for (int imaginaryStart = hasImaginarySign ? realEnd + 1 : realEnd; imaginaryStart >= realEnd; imaginaryStart--) {
// group 4 is followed by [ij]? and the end of the text, and neither starts with a digit,
// so of all the ways group 4 can match, only the longest one of each alternative can succeed
int imaginaryEnd = -1;
int pointEnd = decimalPointEnd(text, imaginaryStart, digitsEnd);
if (pointEnd >= 0 && isImaginaryUnitAndEnd(text, digitsEnd[pointEnd])) {
imaginaryEnd = digitsEnd[pointEnd];
} else if (isImaginaryUnitAndEnd(text, digitsEnd[imaginaryStart])) {
imaginaryEnd = digitsEnd[imaginaryStart];
}
if (imaginaryEnd >= 0) {
return new String[] {
text,
text.substring(0, realStart),
text.substring(realStart, realEnd),
text.substring(realEnd, imaginaryStart),
text.substring(imaginaryStart, imaginaryEnd),
text.substring(imaginaryEnd)
};
}
}
return null;
}
/**
* @return the index after the '.' if {@code [0-9]+\.[0-9]} matches at {@code start}, otherwise -1
*/
private static int decimalPointEnd(String text, int start, int[] digitsEnd) {
int pointIndex = digitsEnd[start];
if (pointIndex > start && pointIndex + 1 < text.length() && text.charAt(pointIndex) == '.'
&& isDigit(text.charAt(pointIndex + 1))) {
return pointIndex + 1;
}
return -1;
}
/** whether {@code ([ij]?)} followed by the end of the text matches at {@code index} */
private static boolean isImaginaryUnitAndEnd(String text, int index) {
int n = text.length();
return index == n || (index == n - 1 && (text.charAt(index) == 'i' || text.charAt(index) == 'j'));
}
private static boolean isDigit(char ch) {
return ch >= '0' && ch <= '9';
}
private static boolean isSign(char ch) {
return ch == '+' || ch == '-';
}
@Override
public ValueEval evaluate(ValueEval[] args, OperationEvaluationContext ec) {
if (args.length != 1) {
return ErrorEval.VALUE_INVALID;
}
return evaluate(ec.getRowIndex(), ec.getColumnIndex(), args[0]);
}
}