Add 3 new routines to Maths category

The routines are:
* PowN
* PowNZN
* PowNZZ

Add compile result for all three for Delphi XE, 11 & 12.
Add test info showing advanced / unit tests

Also updated Pow function entry to cross reference these new routines.

Add test info for PowNxx functions

Author: delphidabbler

collection/633.dat

@@ -0,0 +1,21 @@
+function PowN(const X: Extended; const N: Integer): Extended;
+var
+  I: Integer;
+begin
+  if N = 0 then
+    // IEEE: pown(x, 0) is 1, even when X is zero
+    Exit(1.0);
+  if Math.SameValue(1.0, X) then
+    Exit(1.0);
+  if Math.IsZero(X) then
+  begin
+    if N < 0 then
+      raise SysUtils.EDivByZero.Create('PowN: Negative exponent for X = 0');
+    Exit(0.0);
+  end;
+  Result := 1.0;
+  for I := 1 to System.Abs(N) do
+    Result := Result * X;
+  if N < 0 then
+    Result := 1 / Result;
+end;

collection/634.dat

@@ -0,0 +1,12 @@
+function PowNZN(const X: Integer; const N: Cardinal): Int64;
+var
+  I: Integer;
+begin
+  if (X = 0) and (N > 0) then
+    Exit(0);
+  if X = 1 then
+    Exit(1);
+  Result := 1;
+  for I := 1 to N do
+    Result := Result * X;
+end;

collection/635.dat

@@ -0,0 +1,23 @@
+function PowNZZ(const X: Integer; const N: Integer): Extended;
+var
+  I: Integer;
+  ResultInt: Int64;
+begin
+  if N = 0 then
+    Exit(1.0);
+  if X = 1 then
+    Exit(1.0);
+  if X = 0 then
+  begin
+    if N < 0 then
+      raise SysUtils.EDivByZero.Create('PowNZZ: Negative exponent for X = 0');
+    Exit(0.0);
+  end;
+  ResultInt := 1;
+  for I := 1 to System.Abs(N) do
+    ResultInt := ResultInt * X;
+  if N > 0 then
+    Result := ResultInt
+  else // N < 0
+    Result := 1 / ResultInt;
+end;

collection/maths.ini

@@ -1178,6 +1178,7 @@ FPC=Y
 
 [Pow]
 DescEx="<p>Raises integer value <var>Base</var> to non-negative integer power <var>Exponent</var> and returns the result.</p>"
+SeeAlso=PowN,PowNZN,PowNZZ
 Snip=561.dat
 Delphi2=N
 Delphi3=N
@@ -1197,6 +1198,44 @@ DelphiXE4=Y
 Delphi10S=Y
 FPC=Y
 
+[PowN]
+DescEx="<p>IEEE compliant function that raises real number <var>X</var> to the power <var>N</var>.</p>"
+Extra="<p>See IEEE standard 754-2008 for Floating-Point Arithmetic, page 44.</p>"
+Units=SysUtils,Math
+SeeAlso=Pow,PowNZN,PowNZZ
+TestInfo=advanced
+AdvancedTest.Level=unit-tests
+AdvancedTest.URL="https://github.com/delphidabbler/code-snippets/tree/master/tests/Cat-Maths"
+Snip=633.dat
+DelphiXE=Y
+Delphi11A=Y
+Delphi12A=Y
+
+[PowNZN]
+DescEx="<p>Raises integer <var>X</var> to non-negative integer power <var>N</var>.</p>"
+Extra="<p>Returns an <var>integer</var> value because the power <var>N</var> is non-negative which guarantees that the result is integral.</p><p>Based on IEEE standard 754-2008 for Floating-Point Arithmetic, page 44, but which restricts <var>X</var> to an integer and <var>N</var> to a non-negative integer.</p>"
+SeeAlso=Pow,PowN,PowNZZ
+TestInfo=advanced
+AdvancedTest.Level=unit-tests
+AdvancedTest.URL="https://github.com/delphidabbler/code-snippets/tree/master/tests/Cat-Maths"
+Snip=634.dat
+DelphiXE=Y
+Delphi11A=Y
+Delphi12A=Y
+
+[PowNZZ]
+DescEx="<p>Raises integer <var>X</var> to integer power <var>N</var>.</p>"
+Extra="<p>Returns an <var>Extended</var> value since the result is not an integer when power <var>N</var> is negative.</p><p>Based on IEEE standard 754-2008 for Floating-Point Arithmetic, page 44, but which restricts <var>X</var> to an integer.</p>"
+Units=SysUtils,
+SeeAlso=Pow,PowN,PowNZN
+TestInfo=advanced
+AdvancedTest.Level=unit-tests
+AdvancedTest.URL="https://github.com/delphidabbler/code-snippets/tree/master/tests/Cat-Maths"
+Snip=635.dat
+DelphiXE=Y
+Delphi11A=Y
+Delphi12A=Y
+
 [ResizeRect_A]
 DisplayName="ResizeRect (TSize overload)"
 DescEx="<p>Resizes rectangle <var>R</var> to size <var>NewSize</var>, leaving the top-left position unchanged.</p><p>Returns the resized rectangle.</p>"