'===========================================================================
' Subject: LINE & CIRCLE REPLACEMENTS         Date: 04-14-96 (21:45)       
'  Author: Justin Pasher                      Code: QB, QBasic, PDS        
'  Origin: FidoNet QUIK_BAS Echo            Packet: DEMOS.ABC
'===========================================================================
'> 'I need an algorythm (sp) that will allow me to draw a line without
'> 'using the LINE command. The code below gives you an idea of what
'...

' Here's some code. I converted it from Pascal, so I hope it's all
'correct! Enjoy!

SUB Line (X1, Y1, X2, Y2, Col)
  ' This draws a line from X1,Y1 to X2,Y2
  XLength = ABS(X1-X2)
  DX = SGN(X1-X2)
  YLength = ABS(Y1-Y2)
  DY = SGN(Y1-Y2)
  IF DY = 0 THEN
    IF DX = -1 THEN
      FOR X = X1 TO X2
        PSET(X,Y1),Col
      NEXT
    ELSEIF DX = 1 THEN
      FOR X = X2 TO X1
        PSET(X,Y1),Col
      NEXT
    END IF
    EXIT SUB
  END IF
  IF DX = 0 THEN
    IF DY = -1 THEN
      FOR Y = Y1 TO Y2
        PSET(X1,Y),Col
      NEXT
    ELSEIF DY = 1 THEN
      FOR Y = Y2 TO Y1
        PSET(X1,Y),Col
      NEXT
    END IF
    EXIT SUB
  END IF
  XSlope = XLength/YLength
  YSlope = YLength/XLength
  IF YSlope/XSlope < 1 AND YSlope/XSlope > -1 THEN
    IF DX = -1 THEN
      FOR X = X1 TO X2
        Y = CINT(YSlope*X)
        PSET(X,Y),Col
      NEXT
    ELSEIF DX > 0 THEN
      FOR X = X2 TO X1
        Y = CINT(YSlope*X)
        PSET(X,Y),Col
      NEXT
  ELSE
    IF DY < 0 THEN
      FOR Y = Y1 TO Y2
        X = CINT(XSlope*Y)
        PSET(X,Y),Col
      NEXT
    ELSEIF DY > 0 THEN
      FOR Y = Y2 TO Y1
        X = CINT(XSlope*Y)
        PSET(X,Y),Col
      NEXT
  END IF
END SUB

'> If that algorithm for drawing lines is in ASM could you convert
'> it to QB and send it to me? Anything for a circle?

' Well what do ya know! I do have a circle algorithm! Here 'tis!
'(converted from Pascal again, so you might need a few END IFs.. :)
'NOTE: This algorithm seems to draw the circle where it looks more like
'an ellipse, but it's sorta close to a circle. You can try messing around
'with a few aspects to tweak it out. Laterz...

SUB Circles(X, Y, Rad, Col)
  ' This draws a circle with center X,Y, with Rad as it's radius
  Deg = 0
  DO
    X = CINT(Rad*COS(Deg))
    Y = CINT(Rad*SIN(Deg))
    PSET(X+160,Y+100,Col)
    Deg = Deg + 0.005
  LOOP UNTIL Deg > 6.4
END SUB