2.4
, . . 3- . .
- . , 1 . 1 ( ), - ( ).
:
- : , ,
| = 0 |
Pop
Push()
| . | - | |||
| - | op_um | |||
| abs | op_abs | |||
| + | op_add | push(pop+pop) | ||
| op_sub | buf=pop push(pop-buf) | |||
| * | op_mult | push(pop*pop) | ||
| / | op_div | .... | ||
| % | op_mod | .... | ||
| < | op_less | buf=pop if (pop<buf) then push(1) else push(0) | ||
| > | op_grt | .... | ||
| = | op_equ | .... | ||
| | | op_or | push(pop | pop) | ||
| & | op_and | .... | ||
| ~ | op_not | |||
| op_view | ||||
| op_stop |
| . | - | |||
| >= | op_ | |||
| <= | op_ | |||
| <> | op_ | |||
| !> | op_ | |||
| !< | op_ | |||
| != | op_ | |||
| e2 | op_ | |||
| sign | op_ |
curr_code.op -
curr_code.adr
var[1..v_max] -
code[1..c_max]
| op_pushC | push(curr_code.adr) | ||
| op_pushV _ | push(var[curr_code.adr]) | ||
| op_pop _ | |||
| op_jamp _ | curr_adr = adr_com | ||
| op_jmpC _ | if pop=1 then curr_adr = adr_com else curr_adr=curr_adr + 1 |
|
|
|
:
( )
Procedure VirtComp(
Code array[1..CMAX) of instr, { }
Var array[1..VMAX] of integer) { }
begin
curr_adr:=1; { }
curr_code:=code[curr_adr]; { 1 }
{ ϻ }
while curr_code.op<>op_stop do
begin
{ }
case curr_code.op of
{ }
op_plus: begin push(pop+pop); { }
curr_adr:=curr_adr+1 end;
op_sub: begin buf:=pop; push(pop-buf);
curr_adr:=curr_adr+1 end; { }
........
op_less: begin buf:=pop; { < }
if pop<buf then push(1)
else push(0) end;
........
{ }
op_pushC: begin push(curr_code.adr);
curr_adr:=curr_adr+1 end;
op_pushV: begin push(var[curr_code.adr]]);
curr_adr:=curr_adr+1 end;
{ }
op_jamp: curr_adr:=curr_code.adr;
op_jampC: begin if pop=1
then curr_adr:=curr_code.adr]
else curr_adr:=curr_adr+1 end;
else w_err( )
end{case};
curr_code:=code[curr_adr]; { }
end {while}
end { VirtComp}
( )
1. : {gencode(_, )}
2.
MULT
MULT=id | number | (EXPR)
,
MULT= idP {gencode(op_pushV, P)} |
numberP {gencode(op_pushC, P)} |
(EXPR)
ADD
ADD = MULT { oper MULT }
ADD = MULT { operP {R=P } MULT {gencode(R, 0)} }
EXPR
LOGIC
STMT= id =EXPR
STMT= idP =EXPR {gencode(op_pop, Q)} Q:=P
If typeLex=id then
Begin
Buf=valueLex
Getlex();
EXPR();
Gencode(op_pop, buf)
End
Else if typeLex=view then
VIEW
STMT= view EXPR
STMT= view EXPR {gencode(op_view, 0)}
if typeLex=view then
begin
getlex();
EXPR();
gencode(op_view, 0)
end
else if typeLex=view then
