source("abcd.m")


########################################## 
# an example of 'answ.txt' file
#lambda= 1.064E-6 ;
#Ltot= 1 ;
#r0= 1.0E+100 ;
#w0= 25.63e-6;
#lns1.abcd=abcd_lens( 0.25 ) ;
#lns1.x= 0.37680270021479 ;
#lns2.abcd=abcd_lens( 0.1 ) ;
#lns2.x= 0.90277021575519 ;
#rf=1e100;
#wf=25.630e-6;
########################################## 
source("answ.txt")


q0=waste_r2q(w0,r0,lambda);
optics={lns1,lns2,lns3};

x=0:.001:Ltot;
printf("======== Forward propagation ======\n")
q1=prop(x,q0,0,optics);
w1=q2waste(q1, lambda);
r1=q2radius(q1,lambda);

printf("======== Backward propagation ===\n")
%because of back propagation
rf=-rf;
q1b=waste_r2q(wf,rf,lambda);

q2b=prop(x,q1b,Ltot,optics);
printf("=================================\n")
wb=q2waste(q2b, lambda);
rb=q2radius(q2b,lambda);
plot (x,w1, "1;forward propagation;", x, wb, "2;backward propagation;",
      x,-w1, "1;;", x, -wb, "2;;")

printf("=================================\n")
printf("======= final check =============\n")
printf("======= after propagation ========\n")
printf("following are theoretical values: \n")
w0
r0
wf
rf
q0=waste_r2q(w0,r0,lambda);
qtf=prop(Ltot, q0,0, optics);
printf("values below should match 'wf' and 'rf': \n")
waste = q2waste(qtf, lambda)
radius = q2radius(qtf,lambda)

%pause(100)
%quit()