Yes, definitely. Eventually, I would like to have a nice framework to
make parsing things like this easier and have a nicer, more extensible
API, but for now, I think even simple parsers like this are better
than nothing.
Aaron Meurer
On Wed, Jul 3, 2013 at 10:48 AM, Ondřej Čertík <ondrej.cer...@gmail.com> wrote:
> Pablo,
>
> On Wed, Jul 3, 2013 at 5:38 AM, peibol <pabe...@gmail.com> wrote:
>> It will be something like that. For the moment, I'm just implemented the
>> basics of presentation mathml. I will add features as I need them.
>>
>> After running it, sympify should be called. What do you think about it?
>>
>> def parseMML(mmlinput):
>> from lxml import etree
>> from StringIO import *
>> from lxml import objectify
>> mmlinput= mmlinput.replace(' xmlns="', ' xmlnamespace="')
>> parser = etree.XMLParser(ns_clean=True,remove_pis=True,remove_comments=True)
>> tree = etree.parse(StringIO(mmlinput), parser)
>> objectify.deannotate(tree,cleanup_namespaces=True,xsi=True,xsi_nil=True)
>> mmlinput=etree.tostring(tree.getroot())
>> exppy="" #this is the python expression
>> symvars=[] #these are symbolic variables which can eventually take part in
>> the expression
>> events = ("start", "end")
>> level = 0
>> context = etree.iterparse(StringIO(mmlinput),events=events)
>> for action, elem in context:
>> if (action=='start') and (elem.tag=='mfrac'):
>> level += 1
>> mmlaux=etree.tostring(elem[0])
>> (a,b)=parseMML(mmlaux)
>> symvars.append(b)
>> exppy+=a
>> exppy+='/'
>> mmlaux=etree.tostring(elem[1])
>> (a,b)=parseMML(mmlaux)
>> symvars.append(b)
>> exppy+=a
>> if (action=='end') and (elem.tag=='mfrac'):
>> level -= 1
>> if level:
>> continue
>> if (action=='start') and (elem.tag=='mrow'):
>> exppy+='('
>> if (action=='end') and (elem.tag=='mrow'):
>> exppy+=')'
>> if action=='start' and elem.tag=='mn': #this is a number
>> exppy+=elem.text
>> if action=='start' and elem.tag=='mi': #this is a variable
>> exppy+=elem.text
>> symvars.append(elem.text) #we'll return the variable, so sympy can sympify
>> it afterwards
>> if action=='start' and elem.tag=='mo': #this is a operation
>> exppy+=elem.text
>> return (exppy, symvars)
>>
>>
>> With the example: mmlinput='''<?xml version="1.0"?> <math
>> xmlns="http://www.w3.org/1998/Math/MathML";
>> xmlns:mml="http://www.w3.org/1998/Math/MathML";
>> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
>> xsi:schemaLocation="http://www.w3.org/1998/Math/MathML
>> http://www.w3.org/Math/XMLSchema/mathml2/mathml2.xsd";> <mrow> <mfrac> <mrow>
>> <mn>3</mn> </mrow> <mrow> <mn>57</mn> </mrow> </mfrac> </mrow> </math>'''
>>
>> We get:
>> exppy='((3)/(57))'
>
>
> I think that's a great start. I assume you pass the expression to
> sympify() and obtain a SymPy expression as a result.
>
> Aaron, I think we should have this in sympy, what do you think? We can
> install lxml in .travis.yml and have this tested. If so, I can help
> you Pablo with sending a PR and get it setup.
>
> Ondrej
>
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