Infix Comparison in Marvin

2005-04-16

marvin

infix

Here is a sample Marvin code that converts an infix expression into postfix. I have also posted this one to the InfixComparison page of Concatenative Languages Wiki. (Note from the future: Sadly, these links are broken.)

# infix.mar | Converts an infix expression into postfix

# This implementation uses the global variable space as a hash-table
# for operator precedence.

"listop forth dequeop" use

@|> globs & pushfrom ;

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

@list NONE dpushf __postfix_rec
    {
    dfront NONE =
    iffalse
        dpopf
        repeat
    } { else dpopf eat } ;

@number ;

@postfix NONE dpushf __postfix_rec dpopfall ;
@__postfix_rec [ dup type call ] lmap ;


# define the hash-table for operator precedence
FALSE ^++ ^+- ^-+ ^-- ^*+ ^*- ^** ^*/ ^/+ ^/- ^/* ://
TRUE ^+* ^+/ ^-* :-/

# try one of the examples:
( ( 2 '* ( ( 3 '/ 2 ) '+ 4 ) ) postfix )
dump  # display the stack

yüce's blog

Infix Comparison in Marvin