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Re: How to do Algebraic Mode in PS like the HP does?

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luser.droog wrote:

> luser.droog wrote:
> 
>> David Combs wrote:
>> 
>>> In article <ef3f384c-2a6e-4850-8286-7d75b4b63179@googlegroups.com>,
>>> luser- -droog  <mijoryx@yahoo.com> wrote:
>>>>
>>>>
>>>>I'd suggest you take them one-at-a-time and start posting "How to do XX
>>>>in PS like the HP does?" threads. I'll contribute!
>>>>
>>>>For algebraic mode, we'll need a LL(1) or LR parser. I'll go get my
>>>>Dragon book...
>>>>
>>>>-- droog
>>> 
>>> 
>>> Yes, if it were c, you'd need the lr stuff, I guess.
>>> 
>>> But just parenthesized expressions and function calls,
>>> isn't that basically dead simple?  Recursive descent
>>> or the like.  And so unlike an lr scheme, with
>>> recursive descent the parsing code is readable and
>>> understandable.  (Once someone does the first and
>>> follow sets -- sort of beyond me!)
>>> 
>>> David
>> 
>> Here's a first draft. Converts a string containing
>> an infix expression involving "*_+-" to a string
>> containing the postfix equivalent.
>> 
>> To actually produce PS output, we'll need to expand the
>> payload in the /oper dict and pre-scan the string to
>> count operators so the size of the output string can
>> be calculated.
>>
>  
> A little more searching led me to this:
>
http://devmaster.net/posts/2866/processing-arithmetic-expressions-with-the-shunting-yard-algorithm
> 
> Looks very promising.

Another draft.
This one uses `token` to consume the string,
and evaluates instead of generating a postfix representation.

But I think this makes for a simple, extensible base.  ?maybe?

%!
%infix4.ps

[ %   oper  prec
[ /+  {add} 1    ]
[ /-  {sub} 1    ]
[ /*  {mul} 2    ]
[ /   {div} 2    ]
]
dup /oper exch dup length dict begin {
    dup 0 get exch 1 get def
} forall currentdict end def
dup /prec exch dup length dict begin {
    dup 0 get exch 2 get def
} forall currentdict end def
pop

/opstack 10 array def
/opptr -1 def
/oppush {
    /opptr opptr 1 add def
    opptr opstack length eq { /stackoverflow signalerror } if
    opstack opptr 3 2 roll put
} def
/oppop {
    opptr -1 eq { /stackunderflow signalerror } if
    opstack opptr get
    /opptr opptr 1 sub def
} def

/integertype { } def
/realtype { } def
/nametype {
    dup oper exch known {
        /op exch def
        {
            opptr 0 lt { exit } if
            prec opstack opptr get get
            prec /op load get gt { %prec(tos)>prec(op)
                oper oppop get exec
            }{
                exit
            } ifelse
        } loop
        /op load oppush
    }{
        dup where { exch get } if
    } ifelse
} def
/process {
    dup type exec
} def

/eval {
    {
        token {
            exch /rem exch def
            process
            rem
        }{
            exit
        } ifelse
    } loop
    {
        opptr -1 eq { exit } if
        oper oppop get exec
    } loop
} def



/a 2 def (a = )print a =
/b 3 def (b = )print b =
[
(a + b)
(a * b)
(a + b * b)
(a * b + b)
(a + b / a * b)
(b * b * b / a * b * a)
] { dup print(=)= eval = } forall

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  Re: Is it possible to replace 1 custom character in a font?? Character <Char@cters.bold.italic> - 2012-07-16 17:20 -0700
  Re: Is it possible to replace 1 custom character in a font?? luser- -droog <mijoryx@yahoo.com> - 2012-07-16 20:51 -0700
    Re: Is it possible to replace 1 custom character in a font?? dkcombs@panix.com (David Combs) - 2012-08-13 13:15 +0000
      Re: Is it possible to replace 1 custom character in a font?? luser- -droog <mijoryx@yahoo.com> - 2012-08-13 15:54 -0700
    Re: Is it possible to replace 1 custom character in a font?? dkcombs@panix.com (David Combs) - 2012-08-13 13:48 +0000
      Re: Is it possible to replace 1 custom character in a font?? luser- -droog <mijoryx@yahoo.com> - 2012-08-16 03:09 -0700
        Re: Is it possible to replace 1 custom character in a font?? dkcombs@panix.com (David Combs) - 2012-09-24 06:21 +0000
          How to do Algebraic Mode in PS like the HP does? "luser.droog" <luser.droog@gmail.com> - 2012-09-28 22:48 -0500
            Re: How to do Algebraic Mode in PS like the HP does? "luser.droog" <luser.droog@gmail.com> - 2012-09-30 00:57 -0500
              Re: How to do Algebraic Mode in PS like the HP does? Herbert Voss <Herbert.Voss@alumni.tu-berlin.de> - 2012-09-30 22:40 +0200
                Re: How to do Algebraic Mode in PS like the HP does? "luser.droog" <luser.droog@gmail.com> - 2012-10-02 12:32 -0500
              Re: How to do Algebraic Mode in PS like the HP does? "luser.droog" <luser.droog@gmail.com> - 2012-10-13 01:40 -0500
                Re: How to do Algebraic Mode in PS like the HP does? "luser.droog" <luser.droog@gmail.com> - 2012-10-14 00:51 -0500
                Re: How to do Algebraic Mode in PS like the HP does? "luser.droog" <luser.droog@gmail.com> - 2012-10-14 04:43 -0500
  Re: Is it possible to replace 1 custom character in a font?? SaGS <sags5495@gmail.com> - 2012-08-13 20:04 -0700
  Re: Is it possible to replace 1 custom character in a font?? John Deubert <john@acumentraining.com> - 2012-08-21 06:48 -0700
    Re: Is it possible to replace 1 custom character in a font?? dkcombs@panix.com (David Combs) - 2012-09-24 06:23 +0000

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