ComplexValue.java
/*
* #%L
* nom.tam FITS library
* %%
* Copyright (C) 2004 - 2021 nom-tam-fits
* %%
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package nom.tam.util;
import java.util.StringTokenizer;
import java.util.logging.Logger;
import nom.tam.fits.FitsFactory;
import nom.tam.fits.LongValueException;
/**
* <p>
* A no-frills complex value, for representing complex numbers in FITS headers.
* It is a non-mutable object that is created with a real and imaginary parts, which can be
* retrieved thereafter, and provides string formatting that is suited specifically for
* representation in FITS headers.
* </p>
*
* <p>
* Note that binary tables handle complex data differently, with elements of `float[2]` or
* `double[2]`.
* </p>
*
* @author Attila Kovacs
*
* @since 1.16
*
*/
public class ComplexValue {
private static final Logger LOG = Logger.getLogger(ComplexValue.class.getName());
/** The complex zero **/
public static final ComplexValue ZERO = new ComplexValue(0.0, 0.0);
/** The complex unity along the real axis, or (1.0, 0.0) **/
public static final ComplexValue ONE = new ComplexValue(1.0, 0.0);
/** The unity along the imaginary axis <i>i</i>, or (0.0, 1.0) **/
public static final ComplexValue I = new ComplexValue(0.0, 1.0);
/** The real and imaginary parts */
private double re, im;
/**
* The minimum size string needed to represent a complex value with
* even just single digits for the real and imaginary parts.
*/
private static final int MIN_STRING_LENGTH = 5; // "(#,#)"
/**
* Instantiates a new complex number value with the specified real and imaginary components.
*
* @param re the real part
* @param im thei maginary part
*/
public ComplexValue(double re, double im) {
this.re = re;
this.im = im;
}
/**
* Returns the real part of this complex value.
*
* @return the real part
*
* @see #im()
*/
public final double re() {
return re;
}
/**
* Returns the imaginary part of this complex value.
*
* @return the imaginary part
*
* @see #re()
*/
public final double im() {
return im;
}
@Override
public int hashCode() {
return Double.hashCode(re()) ^ Double.hashCode(im());
}
@Override
public boolean equals(Object o) {
if (o == this) {
return true;
}
if (!(o instanceof ComplexValue)) {
return false;
}
ComplexValue z = (ComplexValue) o;
return z.re() == re() && z.im() == im();
}
/**
* Checks if the complex value is zero. That is, if both the real or imaginary parts
* are zero.
*
* @return <code>true</code>if both the real or imaginary parts are zero.
* Otherwise <code>false</code>.
*/
public final boolean isZero() {
return re() == 0.0 && im() == 0.0;
}
/**
* Checks if the complex value is finite. That is, if neither the real or imaginary parts
* are NaN or Infinite.
*
* @return <code>true</code>if neither the real or imaginary parts are NaN or Infinite.
* Otherwise <code>false</code>.
*/
public final boolean isFinite() {
return Double.isFinite(re()) && Double.isFinite(im());
}
@Override
public String toString() {
return "(" + re() + "," + im() + ")";
}
/**
* Converts this complex value to its string representation with up to the specified
* number of decimal places showing after the leading figure, for both the
* real and imaginary parts.
*
* @param decimals the maximum number of decimal places to show.
* @return the string representation with the specified precision, which
* may be used in a FITS header.
*
* @see FlexFormat
*/
public String toString(int decimals) {
FlexFormat f = new FlexFormat().setPrecision(decimals);
return "(" + f.format(re()) + "," + f.format(im()) + ")";
}
/**
* <p>
* Instantiates a new complex number value from the string repressentation of it in
* a FITS header value. By default, it will parse complex numbers as a comma-separated
* pair of real values enclosed in a bracket, such as <code>(1.0, -2.0)</code>, or
* standard real values, such as <code>123.456</code> or <code>123</code> (as real-only
* values). There can be any number of spaces around the brackets, number components or
* the comma.
* </p>
* <p>
* If {@link FitsFactory#setAllowHeaderRepairs(boolean)} is set <code>true</code>, the
* parsing becomes more tolerant, working around missing closing brackets, different
* number of comma-separated components, and missing empty components. So, for example
* <code>(,-1,abc</code> may be parsed assuming it was meant to be -<i>i</i>.
* </p>
*
* @param text The FITS header value representing the complex number, in brackets
* with the real and imaginary pars separated by a comma. Additional
* spaces may surround the component parts.
* @throws IllegalArgumentException
* if the supplied string does not appear to be a FITS standard
* representation of a complex value.
*
* @see FitsFactory#setAllowHeaderRepairs(boolean)
*/
public ComplexValue(String text) throws IllegalArgumentException {
// Allow the use of 'D' or 'd' to mark the exponent, instead of the standard 'E' or 'e'...
text = text.trim().toUpperCase().replace('D', 'E');
boolean hasOpeningBracket = text.charAt(0) == '(';
boolean hasClosingBracket = text.charAt(text.length() - 1) == ')';
if (!(hasOpeningBracket || hasClosingBracket)) {
// Use just the real value.
re = Double.parseDouble(text);
return;
} else if (!hasOpeningBracket || !hasClosingBracket) {
if (!FitsFactory.isAllowHeaderRepairs()) {
throw new IllegalArgumentException("Missing bracket around complex value: '" + text
+ "'\n\n --> Try FitsFactory.setAllowHeaderRepair(true).\n");
}
LOG.warning("Ignored missing bracket in '" + text + "'.");
}
int start = hasOpeningBracket ? 1 : 0;
int end = hasClosingBracket ? text.length() - 1 : text.length();
StringTokenizer tokens = new StringTokenizer(text.substring(start, end), FitsFactory.isAllowHeaderRepairs() ? ",; \t" : ", ");
if (tokens.countTokens() != 2) {
if (!FitsFactory.isAllowHeaderRepairs()) {
throw new IllegalArgumentException("Invalid complex value: '" + text
+ "'\n\n --> Try FitsFactory.setAllowHeaderRepair(true).\n");
}
LOG.warning("Ignored wrong number of components (" + tokens.countTokens() + ") in '" + text + "'.");
}
if (tokens.hasMoreTokens()) {
re = Double.parseDouble(tokens.nextToken());
}
if (tokens.hasMoreTokens()) {
im = Double.parseDouble(tokens.nextToken());
}
}
/**
* Converts this comlex value to its string representation using up to the
* specified number of characters only. The precision may be reduced as
* necessary to ensure that the representation fits in the allotted space.
*
* @param maxLength the maximum length of the returned string representation
* @return the string representation, possibly with reduced
* precision to fit into the alotted space.
* @throws LongValueException
* if the space was too short to fit the value even
* with the minimal (1-digit) precision.
*/
public String toBoundedString(int maxLength) throws LongValueException {
if (maxLength < MIN_STRING_LENGTH) {
throw new LongValueException(maxLength, toString());
}
String s = toString();
if (s.length() <= maxLength) {
return s;
}
int decimals = FlexFormat.DOUBLE_DECIMALS;
s = toString(decimals);
while (s.length() > maxLength) {
// Assume both real and imaginary parts shorten the same amount...
decimals -= (s.length() - maxLength + 1) / 2;
if (decimals < 0) {
throw new LongValueException(maxLength, toString());
}
s = toString(decimals);
}
return s;
}
}