Re: [xml-dev] Create a special purpose programming language, in XML, usi

[Michael Kay <mike@saxonica.com>]

State machines are essentially flowcharts: programming with GOTOs. 

Have you read Dijkstra: /GOTO statement considered harmful/ ?

https://files.ifi.uzh.ch/rerg/arvo/courses/kvse/uebungen/Dijkstra_Goto.pdf

Michael Kay
Saxonica


On 17 Oct 2013, at 22:39, Costello, Roger L. wrote:

> Hi Folks,
> 
> Occasionally I find that I need to create a special-purpose programming language, to be used to describe how to process XML documents.
> 
> In creating the language I would mimic other programming languages such as Java, e.g.,
> 	
> 	<if>
> 	    <condition>...</condition>
> 	<then>
> 	    <action>...</action>
> 
> and
> 
> 	<while>
> 	    <condition>...</condition>
> 	<do>
> 	    <action>...</action>
> 
> Then I would write an interpreter (using XSLT) to interpret "programs" written in my new programming language.
> 
> However, I recently realized that there is another approach. This illustrates the approach:
> 
> <Machine>
>    <TransitionRules>
>        <Transition currentState="Number" read="0" write="0"
>                            nextState=Number" />
>        <Transition currentState="Number" read="1" write="1"
>                            nextState=Number" />
>        <Transition currentState="Number" read=" " write="0"
>                            nextState=Halt" />
>    </TransitionRules>
> </Machine>
> 
> Instructions and algorithms are expressed using state transition rules.
> 
> The neat thing about this approach is:
> 
> (1) It is very regular. I don't need to invent a bunch of new elements, such as <if> and <while>.
> 
> (2) It is very powerful - it can express any algorithm [1]. 
> 
> (3) No need to constantly extend the language to support new features.
> 
> I was inspired to this approach after reading this fantastic article [2], which represents Turing Machines in XML. 
> 
> Have you created your own special purpose programming language, formatted as XML? If so, what approach did you take to create your language?
> 
> /Roger
> 
> [1] You may recognize that this is essentially a Turing machine. Turing machines are known to be capable of expressing any algorithm.
> 
> [2] See section 2 of:
> http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=F9BABBA74FAEC3276C5DEBC8CC756775?doi=10.1.1.100.3032&rep=rep1&type=pdf
> 
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