(71B) Polynomial Coefficients from a given list of roots -- for the HP-71B

[C.Ret]

HI,

Here is the same task without DATA/READ structure, only one FOR TO NEXT loop and a more convivial interface for output and input :

10 DESTROY A,D,I,R @ OPTION BASE 0 @ DIM A(29) @ A(0)=1
12 INPUT "Add root x.=";R @ D=D+1
14 FOR I= D TO 0 STEP -1 @ IF I>0 THEN A(I)=A(I-1)-R*A(I) ELSE A(0)=-R*A(0)
16 GOSUB 20 @ NEXT I @ PAUSE @ GOTO 12

20 IF A(I)>0 AND I<D THEN DISP "+"; ELSE IF A(I)<0 THEN DISP "-";
22 IF A(I)=0 THEN RETURN ELSE IF ABS(A(I))#1 OR I=0 THEN DISP STR$(ABS(A(I));
24 IF I<1 THEN RETURN ELSE DISP "x"; @ IF I>1 THEN DISP "^"&STR$(I);
26 RETURN

Usage :
New polynomials coefficients are deduce at each step by multiplying the previous polynomial by (x-r). This increase its degree by one unit (variable D indicate polynomial's degree)

1. Start the program with [RUN] or any appropriate method.
2. When prompt, enter value of the root to add and press [END LINE]
3. The actual polynomial is displayed.
4. To continue adding a root from step #2, press [f][CONT]
5. To clear the actual polynomial and restart with a new set of roots, press [RUN]

Example 1:

Code:

>                                 (RUN)
Add root x.=                     1 (END`LINE)
x-1                               (f)(CONT)
Add root x.=                     2 (END`LINE)
x^2-3x+2                          (f)(CONT)
Add root x.=                     3 (END LINE)
x^3-6x^2+11x-6

Example 2:

Code:

x^3-6x^2+11x-6                    (RUN)
Add root x.=                     -1-SQRT(3) (END`LINE)
x+2.73205080757                   (f)(CONT)
Add root x.=                     -1+SQRT(3) (END`LINE)
x^2+2x-2                          (ON)
>_