10 REM ***************************
20 REM *    -TRIAL AND ERROR-    *
30 REM *     SHLOMO GINSBERG     *
35 REM * USE FOR ANY EXPRESSION  *
40 REM *    BY CHANGING LINES    *
45 REM *       150 AND 190       *
50 REM ***************************
60 POKE53280,11:POKE53281,0
70 PRINT"[147]";
80 PRINT"            TRIAL AND ERROR           ";
90 PRINT"           SHLOMO GINSBERG, 1984          "
100 INPUT" INITIAL POINT        ";X
110 INPUT" INITIAL STEP         ";S
120 INPUT" CONVERGENCE CRITERION";C
130 REM
140 I%=0:K=1
150 Y=X*X*X-6*X*X+11*X-6
160 PRINT"[147]CYCLE=";I%;"X=";X;"Y=";Y
165 IFPEEK(197)<>64THEN60000
170 IFABS(Y)<CTHEN280
180 X=X+S:GOTO260
190 Y=X*X*X-6*X*X+11*X-6
200 PRINT"CYCLE=";I%;"X="X;"Y=";Y
205 IFPEEK(197)<>64THEN60000
210 IFABS(Y)<CTHEN280
220 J%=SGN(Y1)*SGN(Y)
230 IFJ%<>1THENK=0.5
240 S=K*J%*S
250 X=X+S
260 Y1=Y:I%=I%+1
270 GOTO190
280 PRINT"             THAT'S ALL FOLKS           "
290 REM    STOP
300 :
60000 PRINT"DO IT AGAIN?"
60010 POKE198,0:WAIT198,1:GETK$:IFK$<>"Y"ANDK$<>"N"THENPOKE53280,RND(1)*15:GOTO60010
60020 IFK$="Y"THENRUN
63000 REM   CONNECT BACK TO LOADSTAR
63010 PRINT"[147]LOAD"CHR$(34)"PAYLOAD"CHR$(34)",8":PRINT"RUN"
63020 POKE631,13:POKE632,13:POKE198,2:END