The Devil in Plain Text

Re:The Devil in Plain Text by Shish2k on Monday May 13, 2013 @08:55AM (#5698354)

His example of how things should work is pretty much 1:1 how the webhelpers.html library works in python:

    >>> from webhelpers.html import literal
    >>> p1, p2 = literal("<p>"), literal("</p>")
    >>> foo = "foo&<bar>"
    >>> type(p1)
    <class 'webhelpers.html.builder.literal'>
    >>> type(foo)
    <type 'str'>
    >>> p1 + foo + p2
    literal(u'<p>foo&amp;&lt;bar&gt;</p>')

And yes, having this sort of thing implemented at the language level, in a generic way that can apply to HTML, SQL, and anything else would be wonderful.

While we're asking for ponies, I'd also like it if "costOfPieInDollars = distanceInMiles + angleInDegrees" would be an error (unless each part was explicitly cast to a compatible type, eg the base int)...

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Re:The Devil in Plain Text by scott_s on Monday May 13, 2013 @11:18AM (#5699130)

The Boost.Units library for C++ does this: http://www.boost.org/doc/libs/1_53_0/doc/html/boost_units/Qu...

Some examples from the documentation:

  quantity<length> L = 2.0*meters;
  quantity<energy> E = kilograms*pow<2>(L/seconds);

  quantity<plane_angle>    theta = 0.375*radians;
  quantity<dimensionless>  sin_theta = sin(theta);
  quantity<plane_angle>    thetap = asin(sin_theta);

I figured Haskell's type system could also do this sort of thing, and it can. I found Dimensional: https://code.google.com/p/dimensional/, but I'm not sure if it's in standard use in the Haskell community. Examples: https://code.google.com/p/dimensional/wiki/IspExample

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Re:The Devil in Plain Text by john_fushi on Monday May 13, 2013 @09:44AM (#5698583)

I'm not sure I understand your last point. Do you desire for compilers to deduce the underlying type from the name of the variable or a type system that would let you create subtypes to give them additional contextual informations that the compiler would then use to enforce integrity?

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Re:The Devil in Plain Text by demetrius on Monday May 13, 2013 @10:08AM (#5698699)

Well, actually Kawa Scheme has a feature called quantities [1]. (+ 1cm 2m) equals to 201.0cm, (+ 1cm 2degr) throws an exception (degr has to be declared first, with (define-base-unit degr "Temperature")).

To tell the truth, I’ve never found any use for this feature.

[1] https://www.gnu.org/software/kawa/Quantities.html

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Re:The Devil in Plain Text by zokier on Monday May 13, 2013 @10:17AM (#5698762)

I'd imagine that such type/units system would be most useful in interactive use, like in WolframAlpha where the system has quite good "understanding" of units and how they should be applied to formulas.

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Re:The Devil in Plain Text by scott_s on Monday May 13, 2013 @12:56PM (#5699797)

It would be very useful in production code as well - consider the case of the Mars Climate Orbiter: http://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_f...

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Re:The Devil in Plain Text by derleth on Monday May 13, 2013 @12:28PM (#5699600)

> I'd also like it if "costOfPieInDollars = distanceInMiles + angleInDegrees" would be an error

Type tagging.

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