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Merge pull request #6130 from ethereum/docs-pragma

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[DOCS] Updates to Pragma docs
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chriseth 2019-03-06 12:07:17 +01:00 committed by GitHub
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docs/introduction-to-smart-contracts.rst
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@ -35,7 +35,7 @@ The first line simply tells that the source code is written for
Solidity version 0.4.0 or anything newer that does not break functionality Solidity version 0.4.0 or anything newer that does not break functionality
(up to, but not including, version 0.6.0). This is to ensure that the (up to, but not including, version 0.6.0). This is to ensure that the
contract is not compilable with a new (breaking) compiler version, where it could behave differently. contract is not compilable with a new (breaking) compiler version, where it could behave differently.
So-called pragmas are common instructions for compilers about how to treat the :ref:`Pragmas<pragma>` are common instructions for compilers about how to treat the
source code (e.g. `pragma once <https://en.wikipedia.org/wiki/Pragma_once>`_). source code (e.g. `pragma once <https://en.wikipedia.org/wiki/Pragma_once>`_).
A contract in the sense of Solidity is a collection of code (its *functions*) and A contract in the sense of Solidity is a collection of code (its *functions*) and

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docs/layout-of-source-files.rst
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@ -13,11 +13,11 @@ and :ref:`pragma directives<pragma>`.
Pragmas Pragmas
======= =======
The ``pragma`` keyword can be used to enable certain compiler features The ``pragma`` keyword is used to enable certain compiler features
or checks. A pragma directive is always local to a source file, so or checks. A pragma directive is always local to a source file, so
you have to add the pragma to all your files if you want enable it you have to add the pragma to all your files if you want enable it
in all of your project. If you :ref:`import<import>` another file, the pragma in all of your project. If you :ref:`import<import>` another file, the pragma
from that file will not automatically apply to the importing file. from that file does not automatically apply to the importing file.
.. index:: ! pragma, version .. index:: ! pragma, version
@ -26,34 +26,34 @@ from that file will not automatically apply to the importing file.
Version Pragma Version Pragma
-------------- --------------
Source files can (and should) be annotated with a so-called version pragma to reject Source files can (and should) be annotated with a version pragma to reject
being compiled with future compiler versions that might introduce incompatible compilation with future compiler versions that might introduce incompatible
changes. We try to keep such changes to an absolute minimum and especially changes. We try to keep these to an absolute minimum and
introduce changes in a way that changes in semantics will also require changes introduce them in a way that changes in semantics also require changes
in the syntax, but this is of course not always possible. Because of that, it is always in the syntax, but this is not always possible. Because of this, it is always
a good idea to read through the changelog at least for releases that contain a good idea to read through the changelog at least for releases that contain
breaking changes, those releases will always have versions of the form breaking changes. These releases always have versions of the form
``0.x.0`` or ``x.0.0``. ``0.x.0`` or ``x.0.0``.
The version pragma is used as follows:: The version pragma is used as follows::
pragma solidity ^0.5.2; pragma solidity ^0.5.2;
Such a source file will not compile with a compiler earlier than version 0.5.2 A source file with the line above does not compile with a compiler earlier than version 0.5.2,
and it will also not work on a compiler starting from version 0.6.0 (this and it also does not work on a compiler starting from version 0.6.0 (this
second condition is added by using ``^``). The idea behind this is that second condition is added by using ``^``). This is because
there will be no breaking changes until version ``0.6.0``, so we can always there will be no breaking changes until version ``0.6.0``, so you can always
be sure that our code will compile the way we intended it to. We do not fix be sure that your code compiles the way you intended. The exact version of the
the exact version of the compiler, so that bugfix releases are still possible. compiler is not fixed, so that bugfix releases are still possible.
It is possible to specify much more complex rules for the compiler version, It is possible to specify more complex rules for the compiler version,
the expression follows those used by `npm <https://docs.npmjs.com/misc/semver>`_. these follow the same syntax used by `npm <https://docs.npmjs.com/misc/semver>`_.
.. note:: .. note::
Using the version pragma will *not* change the version of the compiler. Using the version pragma *does not* change the version of the compiler.
It will also *not* enable or disable features of the compiler. It will just It also *does not* enable or disable features of the compiler. It just
instruct the compiler to check whether its version matches the one instructs the compiler to check whether its version matches the one
required by the pragma. If it does not match, the compiler will issue required by the pragma. If it does not match, the compiler issues
an error. an error.
.. index:: ! pragma, experimental .. index:: ! pragma, experimental