TP3/shell/tests/fixtures/t46_strindex_var.pas

program t46;
(* s[i] with a VARIABLE index -- an address the code can only compute at run
   time.

   Until now a subscript had to fold: ParseSub accepted a constant and
   reported ENoLib for anything else, because off+i is not known when the
   symbol is.  TP3 computes it once, in indstr/ialoop, and holds it in DI
   until the byte is loaded or stored (TPSRC9 1100-1111, 1200-1229); the
   assignment paths then save it across the right-hand side (TPSRC8 asnscal2
   758-760, asnscal3 786-789), which is what keeps `g[i] := h[j]` storing
   where it read from.  This mirrors that: LEA DI,[base] / ADD DI,AX, and a
   PUSH DI around an assignment's right-hand side.

   A STRING is still a length byte at s[0] then the characters, so s[i] is
   the one byte at off+i.  A second subscript is not a type (ESimpType), and
   there is no range check yet -- {$R+} / {$I+} belong to item 2. *)
var
  g : string[10] ;
  h : string[10] ;
  i, j : integer ;
  c : char ;
procedure show (ch : char) ;
begin
  write (ch)
end ;
procedure p ;
var
  l : string[6] ;
  k : integer ;
begin
  l := 'abcdef' ;
  k := 2 ;
  writeln (l[k]) ;                (* local string: LEA DI,[BP+disp] *)
  l[k] := 'Z' ;                   (* local destination, variable index *)
  writeln (l) ;
  g[3] := l[k]                    (* constant destination, variable source *)
end ;
begin
  g := 'hello' ;
  h := 'world' ;
  i := 1 ;
  j := 4 ;
  writeln (g[i]) ;                (* read *)
  c := g[j] ;
  writeln (c) ;                   (* read into a char *)
  g[i] := 'H' ;                   (* write *)
  writeln (g) ;
  if g[i] = 'H' then writeln ('y') else writeln ('n') ;
  writeln (g[j], h[i]) ;          (* two variable reads in one call *)
  show (g[j]) ;                   (* a subscript as a procedure ARGUMENT *)
  writeln ;
  g[i] := h[j] ;                  (* both sides indexed at once *)
  writeln (g) ;
  writeln (g[i+1]) ;              (* computed index: ADD DI,AX *)
  p ;
  writeln (g)
end.