'* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *'
'* Graphical Function Viewer                                   *'
'*                                                             *'
'* File name: GFV.BAS                                          *'
'* Type: Quick Basic Source Code                               *'
'* Version: 1.00                                               *'
'* Created in: May 1998                                        *'
'* Created by: Zsolt Nagy Perge                                *'
'* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *'

DEFINT A-Z
'* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *'
'* Constants                                                   *'
'* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *'
CONST LW = 3                            ' Line Width
CONST Hp = 10                           ' Horizontal Web Precision
CONST Vp = 10                           ' Vertical Web Precision
CONST Pp = 1                            ' Point Precision
CONST Minx = 20                         ' Min (x)
CONST Miny = 20                         ' Min (y)
CONST Maxx = 640 - Hp                   ' Max (x)
CONST Maxy = 480 - Vp                   ' Max (y)
CONST Midx = Minx + (Maxx - Minx) / 2   ' (x) Center
CONST Midy = Miny + (Maxy - Miny) / 2   ' (y) Center
'* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *'
'* Main Program                                                *'
'* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *'
Main:
    SCREEN 12
    CLS
       
    FOR Hc = Minx TO Maxx STEP Hp       ' Put horizontal lines...
        LINE (Hc, Miny)-(Hc, Maxy), 7
    NEXT Hc
    FOR Vc = Miny TO Maxy STEP Vp      ' Put vertical lines...
        LINE (Minx, Vc)-(Maxx, Vc), 7
    NEXT Vc
   
    LINE (Minx, Miny)-(Maxx, Maxy), 14, B   ' Put frame
   
    LINE (0, Midy)-(Maxx, Midy), 15         ' Put center line

    FOR x = 1 TO Maxx - Minx - 1 STEP Pp    ' View Function
       
        'y = x
        'y = x / 8
        'y = SIN(x ^ 2 / 2000) * x / 10
        y = SIN(x ^ 2 / 2000) * 20

        IF y + Midy > Maxy OR x > Maxx - Minx OR x < 1 OR y + Midy - Miny < 1 THEN EXIT FOR
        IF x > 1 THEN
            FOR W = 0 TO LW - 1
                LINE (lx + Minx + W, ly + Midy)-(x + Minx + W, y + Midy), 12
            NEXT W
        END IF
        lx = x
        ly = y
    NEXT x

    BEEP
    SLEEP
    SYSTEM
'* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *'