From 03f66650d37ea5ca5b84d23312585bb3394fecdf Mon Sep 17 00:00:00 2001
From: Gilles Sadowski <erans@apache.org>
Date: Thu, 14 Jul 2011 15:25:11 +0000
Subject: [PATCH] MATH-617 Make "1 + 1i" appear as "1 + i" on formatted output.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1146755 13f79535-47bb-0310-9956-ffa450edef68
---
 .../commons/math/complex/ComplexFormat.java   | 37 ++++++++++++++++++-
 .../complex/ComplexFormatAbstractTest.java    | 32 ++++++++++++++--
 2 files changed, 64 insertions(+), 5 deletions(-)

diff --git a/src/main/java/org/apache/commons/math/complex/ComplexFormat.java b/src/main/java/org/apache/commons/math/complex/ComplexFormat.java
index f64c38737..f3d56096d 100644
--- a/src/main/java/org/apache/commons/math/complex/ComplexFormat.java
+++ b/src/main/java/org/apache/commons/math/complex/ComplexFormat.java
@@ -26,6 +26,7 @@ import org.apache.commons.math.util.CompositeFormat;
 import org.apache.commons.math.exception.util.LocalizedFormats;
 import org.apache.commons.math.exception.MathParseException;
 import org.apache.commons.math.exception.MathIllegalArgumentException;
+import org.apache.commons.math.exception.MathInternalError;
 import org.apache.commons.math.exception.NullArgumentException;
 import org.apache.commons.math.exception.NoDataException;
 
@@ -178,19 +179,51 @@ public class ComplexFormat {
 
         // format sign and imaginary
         double im = complex.getImaginary();
+        StringBuffer imAppendTo = new StringBuffer();
         if (im < 0.0) {
             toAppendTo.append(" - ");
-            CompositeFormat.formatDouble(-im, getImaginaryFormat(), toAppendTo, pos);
+            imAppendTo = formatImaginary(-im, new StringBuffer(), pos);
+            toAppendTo.append(imAppendTo);
             toAppendTo.append(getImaginaryCharacter());
         } else if (im > 0.0 || Double.isNaN(im)) {
             toAppendTo.append(" + ");
-            CompositeFormat.formatDouble(im, getImaginaryFormat(), toAppendTo, pos);
+            imAppendTo = formatImaginary(im, new StringBuffer(), pos);
+            toAppendTo.append(imAppendTo);
             toAppendTo.append(getImaginaryCharacter());
         }
 
         return toAppendTo;
     }
 
+    /**
+     * Format the absolute value of the imaginary part.
+     *
+     * @param absIm Absolute value of the imaginary part of a complex number.
+     * @param toAppendTo where the text is to be appended.
+     * @param pos On input: an alignment field, if desired. On output: the
+     * offsets of the alignment field.
+     * @return the value passed in as toAppendTo.
+     * @throws MathInternalError if {@code absIm} is not positive.
+     */
+    private StringBuffer formatImaginary(double absIm,
+                                         StringBuffer toAppendTo,
+                                         FieldPosition pos) {
+        if (absIm < 0) {
+            throw new MathInternalError();
+        }
+
+        pos.setBeginIndex(0);
+        pos.setEndIndex(0);
+
+        CompositeFormat.formatDouble(absIm, getImaginaryFormat(), toAppendTo, pos);
+        if (toAppendTo.toString().equals("1")) {
+            // Remove the character "1" if it is the only one.
+            toAppendTo.setLength(0);
+        }
+
+        return toAppendTo;
+    }
+
     /**
      * Formats a object to produce a string.  {@code obj} must be either a
      * {@link Complex} object or a {@link Number} object.  Any other type of
diff --git a/src/test/java/org/apache/commons/math/complex/ComplexFormatAbstractTest.java b/src/test/java/org/apache/commons/math/complex/ComplexFormatAbstractTest.java
index f68561e57..b9e3b0ebe 100644
--- a/src/test/java/org/apache/commons/math/complex/ComplexFormatAbstractTest.java
+++ b/src/test/java/org/apache/commons/math/complex/ComplexFormatAbstractTest.java
@@ -42,12 +42,38 @@ public abstract class ComplexFormatAbstractTest {
 
     @Test
     public void testSimpleNoDecimals() {
-        Complex c = new Complex(1, 1);
-        String expected = "1 + 1i";
+        Complex c = new Complex(1, 2);
+        String expected = "1 + 2i";
         String actual = complexFormat.format(c);
         Assert.assertEquals(expected, actual);
     }
 
+    @Test
+    public void testTrimOneImaginary() {
+        final ComplexFormat fmt = ComplexFormat.getInstance(getLocale());
+        fmt.getImaginaryFormat().setMaximumFractionDigits(1);
+
+        Complex c = new Complex(1, 1.04);
+        String expected = "1 + i";
+        String actual = fmt.format(c);
+        Assert.assertEquals(expected, actual);
+
+        c = new Complex(1, 1.09);
+        expected = "1 + 1" + getDecimalCharacter() + "1i";
+        actual = fmt.format(c);
+        Assert.assertEquals(expected, actual);
+
+        c = new Complex(1, -1.09);
+        expected = "1 - 1" + getDecimalCharacter() + "1i";
+        actual = fmt.format(c);
+        Assert.assertEquals(expected, actual);
+
+        c = new Complex(1, -1.04);
+        expected = "1 - i";
+        actual = fmt.format(c);
+        Assert.assertEquals(expected, actual);
+    }
+
     @Test
     public void testSimpleWithDecimals() {
         Complex c = new Complex(1.23, 1.43);
@@ -107,7 +133,7 @@ public abstract class ComplexFormatAbstractTest {
     @Test
     public void testDifferentImaginaryChar() {
         Complex c = new Complex(1, 1);
-        String expected = "1 + 1j";
+        String expected = "1 + j";
         String actual = complexFormatJ.format(c);
         Assert.assertEquals(expected, actual);
     }