sw/src/pascal/POSTFI.PS

   1 PROGRAM POSTFIX(INPUT,OUTPUT);
   2
   3 (* CONVERSION TO POSTFIX FORM *)
   4
   5 VAR CH : CHAR;
   6
   7 PROCEDURE FIND;
   8 BEGIN REPEAT READ(CH)
   9       UNTIL (CH<>" ") AND NOT EOLN
  10 END;
  11
  12 PROCEDURE EXPRESSION;
  13    VAR OP : CHAR;
  14
  15    PROCEDURE TERM;
  16
  17    PROCEDURE FACTOR;
  18    BEGIN IF CH="(" THEN
  19          BEGIN FIND; EXPRESSION;  (* CH =  ) *)
  20          END ELSE WRITE(CH);
  21          FIND
  22    END; (*FACTOR*)
  23
  24    BEGIN FACTOR;
  25          WHILE CH="*" DO
  26          BEGIN FIND; FACTOR; WRITE("*")
  27          END
  28    END; (*TERM*)
  29
  30 BEGIN TERM;
  31    WHILE (CH="+")OR(CH="-") DO
  32       BEGIN  OP := CH; FIND; TERM; WRITE(OP)
  33       END
  34 END; (*EXPRESSION*)
  35
  36 BEGIN FIND;
  37    REPEAT WRITE(" ");
  38       EXPRESSION;
  39       WRITELN
  40    UNTIL CH="."
  41 END.