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Adds first docs
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‎docs/pages/concept.rst

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@@ -58,8 +58,53 @@ To use typeclasses you should understand these steps:
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F2 --> F2
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F2 --> F3["Calling"]
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# TODO: cover each steps
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# TODO: json example for simple types
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Let's walk through this process step by step.
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The first on is "Typeclass definition", where we create a new typeclass:
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.. code:: python
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>>> from classes import typeclass
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>>> @typeclass
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... def json(instance) -> str:
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... """That's definition!"""
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...
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When typeclass is defined it only has a name and a signature
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that all instances will share.
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Let's define some instances:
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.. code:: python
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>>> @json.instance(str)
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... def _json_str(instance: str) -> str:
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... return '"{0}"'.format(instance)
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...
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>>> @json.instance(int)
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... @json.instance(float)
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... def _json_int_float(instance) -> str:
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... return str(instance)
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...
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That's how we define instances for our typeclass.
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These instances will be executed when the corresponding type will be supplied.
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And the last step is to call our typeclass
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with different value of different types:
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.. code:: python
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>>> json('text')
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'"text"'
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>>> json(1)
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'1'
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>>> json(1.5)
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'1.5'
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That's it. There's nothing extra about typeclasses. They can be:
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- defined
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- extended by new instances
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- and called
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singledispatch
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One may ask, what is the difference
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with `singledispatch <https://docs.python.org/3/library/functools.html#functools.singledispatch>`_
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function from the standard library?
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The thing about ``singledispatch`` is that it allows almost the same features.
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But, it lacks type-safety. For example,

‎docs/pages/typesafety.rst

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.. _typesafety:
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13
Type-safety
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===========
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