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Re: Decoding Roman numerals

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  Re: Decoding Roman numerals "WJ" <w_a_x_man@yahoo.com> - 2015-10-09 06:09 +0000
    Re: Decoding Roman numerals "WJ" <w_a_x_man@yahoo.com> - 2015-10-09 06:19 +0000
    Re: Decoding Roman numerals Doug Hoffman <glidedog@gmail.com> - 2015-10-09 07:36 -0400
      Re: Decoding Roman numerals Doug Hoffman <glidedog@gmail.com> - 2015-10-09 08:05 -0400

#42478 — Re: Decoding Roman numerals

WJ wrote:

> Oforth:
> 
> func: char-val {| i |
>   toUpper "IVXLCDM" indexOf --  -> i
>   5 i 2 rem pow  10 i 2 / pow  * }
> 
> func: sign(n, prev) { n prev - ++ sgn  n * }
> 
> func: think( n, prev, total ) { prev n sign   total +   n prev max }
> 
> func: decode {
>   reverse map( #char-val )
>   0 0 rot apply( #think )
>   drop }

Updated for OFORTH version V0.9.21.

: char-val {| i |
  toUpper "IVXLCDM" indexOf 1 -  -> i
  5 i 2 mod pow  10 i 2 / pow  * }

: sign(n, prev) { n prev - 1 +  sgn  n * }

: think( n, prev, total ) { prev n sign   total +   n prev max }

: decode {
  reverse map( #char-val )
  0 0 rot apply( #think )
  drop }

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#42480

WJ wrote:

> : char-val {| i |
>   toUpper "IVXLCDM" indexOf 1 -  -> i
>   5 i 2 mod pow  10 i 2 / pow  * }

Another way:

: char-val {| i |
  toUpper "IVXLCDM" indexOf 1 -  -> i
  5 i isOdd pow  10 i 2 / pow  * }

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#42490

On 10/9/15 2:09 AM, WJ wrote:

> Updated for OFORTH version V0.9.21.
>
> : char-val {| i |
>    toUpper "IVXLCDM" indexOf 1 -  -> i
>    5 i 2 mod pow  10 i 2 / pow  * }
>
> : sign(n, prev) { n prev - 1 +  sgn  n * }
>
> : think( n, prev, total ) { prev n sign   total +   n prev max }
>
> : decode {
>    reverse map( #char-val )
>    0 0 rot apply( #think )
>    drop }

Franck Bensusan has removed the need for matching { ... }
(just end the definition with ;) and has made . polymorphic
so it can be used instead of print.  Also, commas are not
required in the locals input list.  All of these changes will
make Oforth's syntax more familiar to a classic Forther and
need fewer keystrokes.  I added the missing stack comment
for decode:

: char-val | i |
   toUpper "IVXLCDM" indexOf 1 -  -> i
   5 i 2 mod pow  10 i 2 / pow  * ;

: sign( n prev ) n prev - 1 +  sgn  n * ;

: think( n prev total ) prev n sign   total +   n prev max ;

: decode // str --
   reverse map( #char-val )
   0 0 rot apply( #think )
   drop ;

"mcmxxciv" decode .
// => 1984 ok

-Doug

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#42491

On 10/9/15 7:36 AM, Doug Hoffman wrote:

Should be:
> : decode // str -- n

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