Category : Pascal Source Code
Archive   : PAS-SCI.ZIP
Filename : ERFD3.PAS

 
Output of file : ERFD3.PAS contained in archive : PAS-SCI.ZIP
program erfd3; { -> 330 }
{ evaluation of the gaussian error function }

var x,er,ec : real;
done : boolean;

function erf(x: real): real;
{ infinite series expansion of the Gaussian error function }

const sqrtpi = 1.7724538;
tol = 1.0E-4;

var x2,sum,sum1,term: real;
i : integer;

begin
x2:=x*x;
sum:=x;
term:=x;
i:=0;
repeat
i:=i+1;
sum1:=sum;
term:=2.0*term*x2/(1.0+2.0*i);
sum:=term+sum1
until term erf:=2.0*sum*exp(-x2)/sqrtpi
end; { erf }

function erfc(x: real): real;
{ complement of error function }
const sqrtpi = 1.7724538;
terms = 12;

var x2,u,v,sum : real;
i : integer;
begin
x2:=x*x;
v:=1.0/(2.0*x2);
u:=1.0+v*(terms+1.0);
for i:=terms downto 1 do
begin
sum:=1.0+i*v/u;
u:=sum
end;
erfc:=exp(-x2)/(x*sum*sqrtpi)
end; { ercf }

begin { main }
ClrScr;
done:=false;
writeln;
repeat
write('Arg? ');
readln(x);
if x<0.0 then done:=true

else
begin
if x=0.0 then
begin
er:=0.0;
ec:=1.0
end
else
begin
if x<1.5 then
begin
er:=erf(x);
ec:=1.0-er
end
else
begin
ec:=erfc(x);
er:=1.0-ec
end { if }
end;
writeln('X= ',x:8:4,' Erf= ',er:12:8,', Erfc= ',ec:12)
end { if }
until done
end.


  3 Responses to “Category : Pascal Source Code
Archive   : PAS-SCI.ZIP
Filename : ERFD3.PAS
”

  1. Daniel says:
    January 27, 2013 at 3:59 pm

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  2. Joshie says:
    March 18, 2014 at 4:57 pm

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  3. DiskingRound says:
    January 14, 2015 at 10:57 pm

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