String prisms for primitives. #32 #33
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I think I figured it out. |
| object string extends StringInstances | ||
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| trait StringInstances { | ||
| def stringToBoolean: SimplePrism[String, Boolean] = SimplePrism(_.toString, s => Try(s.toBoolean).toOption) |
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In Bounded, you can find a safeCast method that simplifies creation of that kind of Prism
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safeCast doesn't help in this situation, because the string's Ordering and int's boundedness don't help us, as String isn't numeric.
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I could add a new function for constructing prisms catching exceptions.
Where should we put it?
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Shold I rebase and make a new pull request to remove unnessesary stuff from history? |
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What should we do about the identity failing for localized numbers? |
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I really don't know where to put things now with these construction functions.
The exception construction could be maybe put in Prism's object for more intuitive construction for users. |
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No you don't need to rebase. Good points about helper functions, let's put them in the companion object of Prism as you suggested. I will have a read about localised numbers |
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Regarding localised numbers, we should probably make stringToFloat take a Locale and use http://stackoverflow.com/questions/888088/how-do-i-convert-a-string-to-double-in-java-using-a-specific-locale. |
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@julien-truffaut I think it would be much cleaner to just parse only normal numbers. |
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If there is a normal/standard string representation of float and double then let's use it. Otherwise, we can drop string prism for float and double for now. |
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IMO we should keep current Java parsing behavior and possibly pass implicit Locale |
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@13h3r Where should we supply the implicit Locale from? |
NightRa
changed the title
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Another option is to split the string lenses to 2 groups: localized and unlocalized. |
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@NightRa yes, you should import implicit, or import default locale somehow. This avoid us to push system wide parameter into every call |
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Having to import implicits is a usage show stopper from personal experience. (ScalaFX lifting of functions to wrappers) |
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@NightRa It seems that the problem you had is not related to Locale and floating point. I launched test for stringToFloat and DoubleToFloat pass witthout problem. However, Int and Long fails for an interesting reason: some non digits characters are translated to number when you call toInt / toLong on them, see http://www.fileformat.info/info/unicode/char/aa59/index.htm and http://www.alanwood.net/unicode/cham.html |
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@julien-truffaut This is what I was talking about. |
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Ah sorry I misunderstood. Then I think we should limit to basic digit numbers, we can always add more advance prisms later on |
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@julien-truffaut What will we parse with then? |
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We could roll out our own in part of the Int-Digit Isomorphism. #34 |
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let's have a look around if it exists some parser that do the job. Otherwise yes, we can roll our own. |
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Changing branch. |
I have added String prisms for primitives.
ScalaCheck gives out some peculiar counter examples which we have to examine.