Improve PolyGamma(n,0) for negative n

- mtommila/apfloat#54
axkr · Sep 11, 2024 · 6d1219c · 6d1219c
1 parent 9ee01ba
commit 6d1219c
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Showing 5 changed files with 28 additions and 28 deletions.
diff --git a/...library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/SpecialFunctions.java b/...library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/SpecialFunctions.java
@@ -60,6 +60,7 @@
 import org.matheclipse.core.interfaces.IInexactNumber;
 import org.matheclipse.core.interfaces.IInteger;
 import org.matheclipse.core.interfaces.INum;
+import org.matheclipse.core.interfaces.INumber;
 import org.matheclipse.core.interfaces.IRational;
 import org.matheclipse.core.interfaces.IReal;
 import org.matheclipse.core.interfaces.ISymbol;
@@ -1724,15 +1725,17 @@ public IExpr evaluate(final IAST ast, EvalEngine engine) {
             return F.CComplexInfinity;
           }
         }
+        if (arg2.isZero() && arg1.isNumber()) {
+          IReal realPart = ((INumber) arg1).re();
+          if (realPart.isLT(F.CN1)) {
+            // https://github.com/mtommila/apfloat/issues/54
+            // https://functions.wolfram.com/GammaBetaErf/PolyGamma2/03/01/01/0002/
+            return F.C0;
+          }
+        }
         if (engine.isNumericMode()) {
           if (arg1.isZero()) {
             return arg2.digamma();
-            // if (arg2 instanceof ApfloatNum) {
-            // return e1ApfloatArg(((ApfloatNum) arg2).apfloatValue());
-            // }
-            // if (arg2 instanceof ApcomplexNum) {
-            // return e1ApcomplexArg(((ApcomplexNum) arg2).apcomplexValue());
-            // }
           }
           long n = arg1.toLongDefault();
           if (n != Long.MIN_VALUE && arg2.isNumber()) {

diff --git a/..._library/matheclipse-core/src/main/java/org/matheclipse/core/expression/ApcomplexNum.java b/..._library/matheclipse-core/src/main/java/org/matheclipse/core/expression/ApcomplexNum.java
@@ -525,11 +525,8 @@ public ComplexNum complexNumValue() {
 
   @Override
   public int complexSign() {
-    final int i = fApcomplex.real().signum();
-    if (i == 0) {
-      return fApcomplex.imag().signum();
-    }
-    return i;
+    final int signum = fApcomplex.real().signum();
+    return (signum == 0) ? fApcomplex.imag().signum() : signum;
   }
 
   /** @return */

diff --git a/...id_library/matheclipse-core/src/main/java/org/matheclipse/core/expression/ComplexNum.java b/...id_library/matheclipse-core/src/main/java/org/matheclipse/core/expression/ComplexNum.java
@@ -577,11 +577,8 @@ public ComplexNum complexNumValue() {
 
   @Override
   public int complexSign() {
-    final int i = (int) Math.signum(fComplex.getReal());
-    if (i == 0) {
-      return (int) Math.signum(fComplex.getImaginary());
-    }
-    return i;
+    final int signum = (int) Math.signum(fComplex.getReal());
+    return (signum == 0) ? (int) Math.signum(fComplex.getImaginary()) : signum;
   }
 
   public Complex complexValue() {

diff --git a/...id_library/matheclipse-core/src/main/java/org/matheclipse/core/expression/ComplexSym.java b/...id_library/matheclipse-core/src/main/java/org/matheclipse/core/expression/ComplexSym.java
@@ -325,13 +325,8 @@ public ComplexNum complexNumValue() {
 
   @Override
   public int complexSign() {
-    final int i = fReal.numerator().complexSign();
-
-    if (i == 0) {
-      return fImaginary.numerator().complexSign();
-    }
-
-    return i;
+    final int signum = fReal.numerator().complexSign();
+    return (signum == 0) ? fImaginary.numerator().complexSign() : signum;
   }
 
   /** {@inheritDoc} */

diff --git a/..._library/matheclipse-core/src/test/java/org/matheclipse/core/system/GammaBetaErfTest.java b/..._library/matheclipse-core/src/test/java/org/matheclipse/core/system/GammaBetaErfTest.java
@@ -1237,8 +1237,16 @@ public void testPolyGamma() {
     // TODO
     check("N(PolyGamma(-2,3/2),30)", //
         "PolyGamma(-2,1.5)");
+    check("N(PolyGamma(-I*1.0,0),30)", //
+        "PolyGamma(I*(-1),0)");
+    // TODO calculate for complex n:
+    checkNumeric("PolyGamma(6+I,2.5+3*I)", //
+        "PolyGamma(6.0+I*1.0,2.5+I*3.0)");
+
     check("N(PolyGamma(-2,0),30)", //
-        "PolyGamma(-2,0)");
+        "0");
+    check("N(PolyGamma(-2-I*1,0),30)", //
+        "0");
 
     check("PolyGamma(0,-42)", //
         "ComplexInfinity");
@@ -1257,10 +1265,10 @@ public void testPolyGamma() {
     check("PolyGamma(-2)", //
         "ComplexInfinity");
 
-    // TODO calculate for complex n:
-    checkNumeric("PolyGamma(6 + I, 2.5 + 3 I)", //
-        "PolyGamma(6.0+I*1.0,2.5+I*3.0)");
-
+    checkNumeric("PolyGamma(-2.5 + 3*I)", //
+        "1.4452083452957394+I*2.358508608801951");
+    checkNumeric("PolyGamma(2.5 + 3*I)", //
+        "1.2812739190662312+I*0.9798053153445596");
 
     checkNumeric("PolyGamma(0, 0.166667)", //
         "-6.332115068746184");