# HP Forums

Full Version: Program NEWT2
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Hi,

The program below is to my opinion an improved working variation on the program provided by Han. The original version led to an error message.

Original version

EXPORT NEWT2()
BEGIN LOCAL n, xold, xnew, err, N, f;

N := 100; err := .00001; xnew := 1;

IF INPUT(
{f, xnew, err, N},
"Newton's Method",
{"f(X) = ", "Guess = ", "Error = ", "Max Iter. = "},
{
"Enter the function surrounded by single quotes",
"Enter the initial guess",
"Enter the tolerance",
"Enter the maximum number of iterations"
},
{f, xnew, err, N}
) THEN F1 := f;

CAS("F0 := id-F1/F1'");
L1 := {}; L1(1) := xnew;
FOR n FROM 2 TO N+1 DO xold := xnew;
xnew := F0(xold);
L1(n) := xnew;
IF ABS(xnew-xold) < err THEN break; END;
END;
EDITLIST(L1);

END;

Improved version

EXPORT NEWT2

BEGIN

LOCAL n, xold, xnew, err, N, f;

N := 100; err := .00001; xnew := 1;
f:='X';

// By defining f as'X' as a default value
// the program works

IF INPUT(
{f, xnew, err, N},
"Newton's Method",
{"f(X) = ", "Guess = ", "Error = ", "Max Iter. = "},
{
"Enter the function surrounded by single quotes",
"Enter the initial guess",
"Enter the tolerance",
"Enter the maximum number of iterations"
},
{f, xnew, err, N}
) THEN F1 := f;

CAS("F0 := id-F1/F1'");
L1 := {}; L1(1) := xnew;
FOR n FROM 2 TO N+1 DO xold := xnew;
xnew := F0(xold);
L1(n) := xnew;
IF ABS(xnew-xold) < err THEN break; END;
END;
EDITLIST(L1);

END;
END;
Reference URL's
• HP Forums: https://www.hpmuseum.org/forum/index.php
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