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Clarify scope of 'using A for B' (#4252)

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* Issue 1213: Clarify scope of 'using A for B'

* Typo fix.

* Further restructuring and clarification of contracts doc.

* Revert closer to original wording and formatting.
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Mike 2018-06-29 12:21:39 +02:00 committed by chriseth
parent c9cab80389
commit 2a9d54af58
1 changed files with 12 additions and 11 deletions
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docs/contracts.rst
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@ -1402,24 +1402,25 @@ Using For
*********
The directive ``using A for B;`` can be used to attach library
functions (from the library ``A``) to any type (``B``).
functions (from the library ``A``) to any type (``B``).
These functions will receive the object they are called on
as their first parameter (like the ``self`` variable in
Python).
as their first parameter (like the ``self`` variable in Python).
The effect of ``using A for *;`` is that the functions from
the library ``A`` are attached to any type.
the library ``A`` are attached to *any* type.
In both situations, all functions, even those where the
type of the first parameter does not match the type of
the object, are attached. The type is checked at the
In both situations, *all* functions in the library are attached,
even those where the type of the first parameter does not
match the type of the object. The type is checked at the
point the function is called and function overload
resolution is performed.
The ``using A for B;`` directive is active for the current
scope, which is limited to a contract for now but will
be lifted to the global scope later, so that by including
a module, its data types including library functions are
The ``using A for B;`` directive is active only within the current
contract, including within all of its functions, and has no effect
outside of the contract in which it is used. The directive
may only be used inside a contract, not inside any of its functions.
By including a library, its data types including library functions are
available without having to add further code.
Let us rewrite the set example from the