CAD in Civil Engineering - Baustatik-Info-Server

Page 38 Computer Languages for Engineering - SS 136768 c reel branch69 if (d .lt. 0.) goto 5507071 d = dsqrt(d)72 x1 = (-b +d)/(2.e0*a)73 x2 = (-b -d)/(2.e0*a)7475 write(*,*) ’quadratic case, reel values’76 write(*,*) ’ x1 = ’,x177 write(*,*) ’ x2 = ’,x27879 goto 6008081 c complex branch82 550 continue8384 d = dsqrt(-d)85 x1r = -b/(2.e0*a)86 x2r = x1r87 x1i = d/(2.e0*a)88 x2i = -d/(2.e0*a)8990 write(*,*) ’quadratic case, complex values’91 write(*,*) ’ x1 = ’,x1r,’ +i ’,x1i92 write(*,*) ’ x2 = ’,x2r,’ +i ’,x2i9394 600 continue95 end2.9.2.4 Quadratic Equation, Solver Implementation Fortran 90 likeThe following code implements the solution of a quadratic equation (see equation 2.5) in a Fortran 90version. Note, that we are able to implement the case tree without any goto jumps, which were essentialin an 66 approach.Listing 2.20: Implementation of a 90-Quad-Solver1 ! Solver for a quadratic equation2 ! Implementation in Fortran903 program quadequation45 implicit none ! only explicit declarations67 real(8)::a, b, c ! parameters of the equation8 real(8)::d ! discriminant9 real(8)::p ! precision10 real(8)::x1,x2 ! for the real solutions11 real(8)::x1r,x1i,x2r,x2i! for the complex solutions1213 ! setup the parameters for the quadratic equation14 a = 1.15 b = 0.16 c =-4.E. Baeck