Infix to Postfix Converter Class in Marvin

2005-04-16

marvin

infix

postfix

Here is an object oriented version of the infix to postfix converter written in Marvin:

# infixoop.mar | Converts an infix expression into postfix

# This implementation uses the object data as a hash-table
#    for operator precedence.

"listop forth dequeop" use

@@Infix
    @new  # define the hash-table for operator precedence
        FALSE ^++ ^+- ^-+ ^-- ^*+ ^*- ^** ^*/ ^/+ ^/- ^/* ://
        TRUE ^+* ^+/ ^-* :-/ me ;

    @|> & pushfrom ;

    @string dfront NONE =
        { iftrue dpushf }
        { else
            dpopf 2dup me .|>
            { iftrue swap dpushf }
            { else dpushf dpushf }
        } ;

    @list NONE dpushf me .__topostfix_rec
        {
        dfront NONE =
        iffalse
            dpopf
            repeat
        } { else dpopf eat } ;

    @number ;

    @topostfix NONE dpushf me .__topostfix_rec dpopfall ;
    @__topostfix_rec [ dup type callme ] lmap ;
;;

# try one of the examples:
'Infix new :infix
( ( 2 '* ( ( 3 '/ 2 ) '+ 4 ) ) %infix .topostfix )

dump  # display the stack

yüce's blog

Infix to Postfix Converter Class in Marvin