HP 34S: Find an element in a matrix?

[Gerald H]

Can someone please explain the syntax/function of MFD?

I need to find a given matrix element to implement Shanks square form factorization method.

[Thomas Klemm]

From the code I'd say: ( y mat -> r )
Where mat is a matrix descriptor and y is the element you search.

Cheers
Thomas

Code:

/* Find a specified element in a matrix
 */
            LBL'MFD'
            ABS
            M-ALL
            x[<->] Y
m_find_loop::       x=?[->]Y
            JMP m_found
            ISG Y
            JMP m_find_loop
m_found::       DROP
            RTN

[Gerald H]

To post #2:

Thank you.

I don't understand r.

For 5,6,7,8 stored in registers 20 to 23

stack y: 55 x: 20.0401 returns 24.02301

and

stack y: 7 x: 20.0401 returns 22.02301

Presumably the second result indicates "found"? How should this result be interpreted?

[Thomas Klemm]

You probably want the index of the element. The matrix descriptor is still in the last x register. Therefore you can use:

Code:

RCL L
M.IJ

For 7 you get (x, y) = (3, 1). For 55 you get an Error: Out of range.

[Gerald H]

To post #4:

Thank you & yes that is the info I needed.

Will now get to work on Shanks SQFF.