ON ERROR GOTO 10
DIM f AS DOUBLE, y AS DOUBLE, x AS DOUBLE, paso AS DOUBLE
CLS
SCREEN 12
f = 1
l = 1
yy = 1: y = 2
REM ***************** colores *******************
c1 = 8: c2 = 3: c3 = 12: c4 = 15

REM *********************** coef sirve para ampliar la imagen **************
coef = 100

REM *** paso sirve para la precison/velocidad *****************************
REM *********** ejemplo:    paso=1 ->rapido;       paso=0.05->preciso  ****
paso = .2

FOR n = 0 TO 320 / coef: LINE (n * coef + 320, 0)-(n * coef + 320, 479), c1: LINE (-n * coef + 320, 0)-(-n * coef + 320, 479), c1: NEXT
FOR n = 0 TO 240 / coef: LINE (0, n * coef + 240)-(639, n * coef + 240), c1: LINE (0, -n * coef + 240)-(639, -n * coef + 240), c1: NEXT
LINE (0, 240)-(639, 240), c2
LINE (320, 0)-(320, 479), c2

5 f = f + paso: IF ABS(f - INT(f)) < .02 THEN f = INT(f)
 IF f >= 640 THEN a$ = INPUT$(1): END
 x = (f - 320) / coef


 dy = (y - yy) / (paso / coef)
 yy = y
REM ************************* aqui va la funcion y=x... ********************
'y = 1 / (x - 1)
'y = (TAN(x)) ^ SIN(x)
'y = LOG(x - 1)
'y = INT((x / ABS(x)) + .5) * 2 / ((1 - ABS(x)) ^ 3)
'r0 = 10
'r1 = 20
' y = 10 / (1 + r0 * ((r1 + x) / (r1 * x)))
'y = x
y = x * x

IF ABS(dy * coef < 240) THEN PSET (f, 240 - (dy * coef)), 4

IF (ABS(y * coef) < 240) THEN PSET (f, 240 - (y * coef)), c4




GOTO 5

REM ****** si hay division por 0, etc dibuja la asintota ****************
10 kk = k: k = INT(f): IF k = kk THEN GOTO 11:  ELSE l = -l: IF l = 1 THEN LINE (k, 0)-(k, 479), c3, , &H5555:  ELSE LINE (k, 1)-(k, 479), c3, , &H5555
'PRINT ERL
11 RESUME 5