program t89_varstr;

{ t89 -- VAR string parameters.  CALC.INC's GetFileName is

      procedure GetFileName(var Line : AnyString; FileType : String3);

  and the callee must operate on the CALLER's string, not on a copy.  This
  exercises the address slot for the whole variable, a constant-index element
  (x[1]), a variable-index element (x[i]), Length, assignment of a literal and
  of a concatenation, and a function whose formal is VAR string.

  Hand-derived output:
      hello        setit copies the literal through the caller's address
      5            Length reads the length byte through that address
      Hello!       upd writes x[1] and x[0], then appends through the address
      H            the same element read back
}

var
  S : string[10];
  I : integer;

procedure setit (var X : string[10]);
begin
  X := 'hello'
end;

procedure upd (var X : string[10]);
var
  I : integer;
begin
  X[1] := 'H';
  X[0] := chr (5);
  for I := 1 to Length (X) do
    X[I] := X[I];
  X := X + '!'
end;

function size (var X : string[10]) : integer;
begin
  size := Length (X)
end;

begin
  setit (S);
  writeln (S);
  writeln (size (S));
  upd (S);
  writeln (S);
  I := 1;
  writeln (S[I])
end.