Requesting ELSEIF

[toml_12953]

(03-24-2017 05:38 PM)Han Wrote:  CASE blocks have similar logic to nested ELSE-IF blocks (exiting the block once a condition is met and relevant actions are executed). It doesn't make your code any shorter but can provide improved legibility.

Just to show you, here's the actual ANSI/ISO BASIC statement statement I'm converting:

PHP Code:

IF (t = 1) OR (t = 2) OR (t = 3) THEN
! circle, ellipse, or hyperbola
   LET Xo = -Dr/(2*Ar)
   LET Yo = -Er/(2*Cr)
   PRINT "translation = {"; USING$("-%.####",Xo); ", "; USING$("-%.####",Yo); "}"
   LET r(1) = Ar/(Ar*Xo*Xo + Cr*Yo*Yo - Fr)
   LET r(3) = Cr/(Ar*Xo*Xo + Cr*Yo*Yo - Fr)
   LET r(6) = -1.0
   IF ABS(r(1)) < ABS(r(3)) THEN    ! foci on x-axis
      LET a2 = ABS(1 / r(1))
      LET b2 = ABS(1 / r(3))
      IF t = 2 THEN                 ! ellipse
         LET c1 = SQR( a2 - b2 )
         PRINT "foci = {±"; USING$("-%.####",c1); ", 0.0000}"
         PRINT "eccentricity ="; USING$("-%.#####",c1 / SQR(a2))
      ELSEIF t = 3 THEN            ! hyperbola
         LET c1 = SQR( a2 + b2 )
         PRINT "foci = {±"; USING$("-%.####",c1); ", 0.0000}"
         PRINT "eccentricity ="; USING$("-%.#####",c1 / SQR(a2))
      END IF
   ELSE                             ! foci on y-axis
      LET a2 = ABS(1 / r(3))
      LET b2 = ABS(1 / r(1))
      IF t = 2 THEN                 ! ellipse
         LET c1 = SQR( a2 - b2 )
         PRINT "foci = {0.0000, ±"; USING$("-%.####",c1); "}"
         PRINT "eccentricity ="; USING$("-%.#####",c1 / SQR(a2))
      ELSEIF t = 3 THEN            ! hyperbola
         LET c1 = SQR( a2 + b2 )
         PRINT "foci = {0.0000, ±"; USING$("-%.####",c1); "}"
         PRINT "eccentricity ="; USING$("-%.#####",c1 / SQR(a2))
      END IF
   END IF
ELSEIF t = 4 THEN                   ! parabola
   IF ABS(Ar) > ABS(Cr) THEN        ! form: x² - 4·p·y = 0
      LET Xo = Dr/(2*Ar)
      LET Yo = (Fr - Dr*Dr/(4*Ar))/Er
      PRINT "translation = {"; USING$("-%.####",Xo); ", "; USING$("-%.####",Yo); "}"
      LET r(1) = 1
      LET r(5) = Er / Ar
      LET p = -r(5)/4
      PRINT "focus = {0, "; USING$("-%.####",p); "}"
   ELSE                            ! form: y² - 4·p·x = 0
      LET Xo = (Fr - Er*Er/(4*Cr))/Dr
      LET Yo = Er/(2*Cr)
      PRINT "translation = {"; USING$("-%.####",Xo); ", "; USING$("-%.####",Yo); "}"
      LET r(3) = 1
      LET r(4) = Dr / Cr
      LET p = -r(4)/4
      PRINT "focus = {"; USING$("-%.####",p); ", 0}"
   END IF
END IF