Re: [Pyparsing] fourFn.py explanation and slight modification

[Glenn P. <gle...@gm...>]

Hmm I got it going with this

        point = Literal( "." )
        e     = CaselessLiteral( "E" )
        fnumber = Combine( Word( "+-"+nums, nums ) +
                           Optional( point + Optional( Word( nums ) ) ) +
                           Optional( e + Word( "+-"+nums, nums ) ) )
        ident = Word(alphas, alphas+nums+"_$")
        plus  =  Literal( "+" )
        minus =  Literal( "-" )
        mult  =  Literal( "*" )
        div   =  Literal( "/" )
        lte   =  Literal( ">=" )
        lt    =  Literal( "<" )
        gt    =  Literal( ">" )
        anding = CaselessLiteral( "and" )
        oring =  CaselessLiteral( "or" )
        lpar  =  Literal( "(" ).suppress()
        rpar  =  Literal( ")" ).suppress()
        addop  = plus | minus | lte | lt | gt
        multop = mult | div
        logicalop = anding | oring
        expop = Literal( "^" )
        pi    = CaselessLiteral( "PI" )
        expr = Forward()
        atom = ((Optional(oneOf("- +")) +

 (pi|e|fnumber|ident+lpar+expr+rpar).setParseAction(self.pushFirst))
                | Optional(oneOf("- +")) + Group(lpar+expr+rpar)
                ).setParseAction(self.pushUMinus)
        # by defining exponentiation as "atom [ ^ factor ]..." instead of
        # "atom [ ^ atom ]...", we get right-to-left exponents, instead of
left-to-right
        # that is, 2^3^2 = 2^(3^2), not (2^3)^2.
        factor = Forward()
        factor <<= atom + ZeroOrMore( ( expop + factor ).setParseAction(
self.pushFirst ) )
        term = factor + ZeroOrMore( ( multop + factor ).setParseAction(
self.pushFirst ) )
        term2 = term + ZeroOrMore( ( addop + term ).setParseAction(
self.pushFirst ) )
        expr <<= term2 + ZeroOrMore( ( logicalop + term2 ).setParseAction(
self.pushFirst ) )


Can't say I 100% understand the grammer though. Any short explanations
would be great.




On 4 September 2014 10:23, Glenn Pierce <gle...@gm...> wrote:

> Hi I am new to pyparsing and I am having trouble understanding the grammer
> of the example fourFn.py
> <http://pyparsing.wikispaces.com/file/view/fourFn.py/30154950/fourFn.py>
>
> I am trying to add comparison operators and logical operators to this
> example. The comparisons work ok but I not sure how to add the logical
> operators AND OR NOT
>
> So far I have this
>
>         plus  =  Literal( "+" )
>         minus =  Literal( "-" )
>         mult  =  Literal( "*" )
>         div   =  Literal( "/" )
>         lte   =  Literal( ">=" )
>         lt    =  Literal( "<" )
>         gt    =  Literal( ">" )
>         anding = CaselessLiteral( "and" )
>         lpar  =  Literal( "(" ).suppress()
>         rpar  =  Literal( ")" ).suppress()
>         addop  = plus | minus | lte | lt | gt
>         multop = mult | div
>          expop = Literal( "^" )
>         pi    = CaselessLiteral( "PI" )
>         sensor_values = CaselessLiteral( "sensor_values" )
>         expr = Forward()
>          atom = ((Optional(oneOf("- +")) +
>
>  (sensor_values|pi|e|fnumber|ident+lpar+expr+rpar).setParseAction(self.pushFirst))
>                 | Optional(oneOf("- +")) + Group(lpar+expr+rpar)
>                 ).setParseAction(self.pushUMinus)
>         # by defining exponentiation as "atom [ ^ factor ]..." instead of
>         # "atom [ ^ atom ]...", we get right-to-left exponents, instead of
> left-to-right
>         # that is, 2^3^2 = 2^(3^2), not (2^3)^2.
>         factor = Forward()
>         factor <<= atom + ZeroOrMore( ( expop + factor ).setParseAction(
> self.pushFirst ) )
>         term = factor + ZeroOrMore( ( multop + factor ).setParseAction(
> self.pushFirst ) )
>         expr <<= term + ZeroOrMore( ( addop + term ).setParseAction(
> self.pushFirst ) )
>
>
> Could someone perhaps explain the three lines below and how I would add my
>  CaselessLiteral( "and" ) boolean
> so I could do something like
> nsp.eval('10 >= 5 AND 10 < 15')
>
> factor <<= atom + ZeroOrMore( ( expop + factor ).setParseAction(
> self.pushFirst ) )
>  term = factor + ZeroOrMore( ( multop + factor ).setParseAction(
> self.pushFirst ) )
> expr <<= term + ZeroOrMore( ( addop + term ).setParseAction(
> self.pushFirst ) )
>
>
>  PS what is the <<= operator ? I can't find the docs for it
>
> Thanks for any help.
>