unit Unit2;

interface
Function BETA(Z,W:REAL):REAL;
Function GAMMLN(xx:real):real;

implementation
Function GAMMLN(xx:real):real;
const
  STP=2.50662827465; HALF=0.5; ONE=1.0; FPF=5.5;
var
  x,tmp,ser:double;
  j:integer;
  cof:array[1..6] of double;
BEGIN
  COF[1]:=76.18009173;      COF[2]:=-86.50532033;
  COF[3]:=24.01409822;      COF[4]:=-1.231739516;
  COF[5]:= 0.120858003e-2;  COF[6]:=-0.536382e-5;
  X:=XX-ONE;
  TMP:=X+FPF;
  TMP:=(X+HALF)*Ln(TMP)-TMP;
  SER:=ONE;
  For J:=1 To 6 do
    BEGIN
      X:=X+ONE;
      SER:=SER+COF[J]/X
    END;
  GAMMLN:=TMP+Ln(STP*SER);
end;

Function BETA(Z,W:real):real;
begin
  BETA:=Exp(GAMMLN(Z)+GAMMLN(W)-GAMMLN(Z+W))
end;

end.