Question: Text plotting and select from list

restart

#with( RationalTrigonometry)

P1:=[-1,3]:P2:=[4,5]:

# shift operates as such mp:=P1+shift*(P2-P1). It's default value 0.5 It moves
#   the text along between P1 and P2
# shift and shift are optional inputs to move individual test pieces.
#If Q contains shift then use it else use shift
  qp:=P1+shift*(P2-P1) or qp:=P1+shift*(P2-P1)
#Similarily for vec

Qdim([P1,typeset("P1=",P1),align=[left],colour=red] ,
     [P2,typeset("P2=",P2),align=[right],colour=purple] ,
      Q=[Q_12,align =[below,right],shift=0.6] ,
      point=[symbolsize=12,symbol=solidcircle,colour=blue,shift=0.4] ,
      vec=[typeset("v[12]=",P2-P1),align=[below,right],shift=0.1],
      shift=0.7):  

#The definition input of the procedure is

#proc(P1, P2,
#    {Q:=[ NULL,:-align={':-left'}]},
#        {corp::{"cart","proj"}:="cart"},
#        {shift:=0.5},
#        {vec::list:=[]},
#        {scale::{list,integer}:=1},
#        {leader::{-1,0,1}:= 1},
#        {dimoffset::{1/6,1/5,1/4,3/4,2/3,1/2,1/3,1,3/2,2,3,4,5,6}:=1},
#        {point::list:=['color' = ':-blue', symbol = ':-solidcircle', 'symbolsize' = 8]},
#        {line::list:=['thickness'=3]},
#        {plopts::list:=[]})

restart

Q:=[Q_12,shift=0.6,align =[below,right]]  
      
      

nops(Q)

for i to nops(Q) do
 if has([op(Q[i])],`shift`) then
 qp:=rhs(Q[i]);
 print(i,qp);
 break;
end if;
end do;