[clean-list] Parsing: to drill or not to drill, that is the question

[zuurb078 at planet.nl]

I just wrote constantWind to be working on a list of Char. Only after that I found out I wanted to combine it with parsers working on a list of [Char]. It shows that you can reuse the constantWind parser without having to re-engineer it to work on a list of [Char]. you could have done the latter also.
Erik Zuurbier

________________________________

Van: clean-list-bounces at science.ru.nl namens metaperl
Verzonden: do 28-8-2008 16:30
Aan: clean-list at science.ru.nl
Onderwerp: [clean-list] Parsing: to drill or not to drill, that is the question




surfaceWind is a parser engineered to operate on [Char]

however constantWind is a parser engineered to operate on Char... but it
then gets applied via drill to create a parser which operates on [Char]

Why would one be indirect and create a parser to operate on Char and then
apply 'drill' to get what you intended to use:

surfaceWind :: Parser [Char] SurfaceWind t
surfaceWind = "Surface Wind" :> p
where   p       = (word constantWind) <&> \surfaceWind -> <!?> (word
directionVariation)
                                                        (\dir2->{surfaceWind & direction=dir2}) // if found
                                                        surfaceWind                                     // if nothing found

constantWind :: Parser Char SurfaceWind a
constantWind =  direction       <&> \dir         ->
                                speed           <&> \(u,spd) ->
                                gust u          <@  \g           -> {direction=dir,speed=spd,gust=g}

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