Algebraic to RPN

[Han]

(02-25-2017 02:05 PM)compsystems Wrote:  extract parts and operators with [] acts as the PART command, please create a second version with PART cmd

PHP Code:

(x^2-4*x)[1] → '+'
(x^2-4*x)[2] → x^2
(x^2-4*x)[3] → -4*x

part(x^2-4*x) → 2
part(x^2-4*x,1) → x^2
part(x^2-4*x,2) → -4*x
part(x^2-4*x,0) → "+" 


I am not sure why you would want a version using the part command, but here:

Code:

#pragma mode( separator(.,;) integer(h32) )
#cas
CRPN(f):=
begin
  local rpn, op, par, n, j, g;

  rpn:="";
  op:="";
  par:="";
  if (type(f) <> DOM_SYMBOLIC) then
    rpn:=string(f);
    return(rpn);
  end;

  op:=string(part(f,0));
  n:=size(op);
  op:=MID(op,2,n-2);
  n:=part(f);

  for j from 1 to n do
    g:=part(f,j);
    if (type(g) <> DOM_SYMBOLIC) then
      par:=string(g);
    else
      par:=CRPN(g);
    end;
    if (j > 1) then rpn:=rpn + " "; end;
    rpn:=rpn + par;
    if ((j > 1) or (n == 1)) then
      rpn:=rpn + " " + op;
    end;
  end;

  return(rpn);
end;
#end