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Merge pull request #11314 from ethereum/patch-1

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[DOCS] Removed an overflow check and rely on checked arithmetic
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chriseth 2021-04-26 14:39:17 +02:00 committed by GitHub
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docs/introduction-to-smart-contracts.rst
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@ -105,7 +105,6 @@ registering with a username and password, all you need is an Ethereum keypair.
// Can only be called by the contract creator
function mint(address receiver, uint amount) public {
require(msg.sender == minter);
require(amount < 1e60);
balances[receiver] += amount;
}
@ -205,10 +204,15 @@ always the address where the current (external) function call came from.
The functions that make up the contract, and that users and contracts can call are ``mint`` and ``send``.
The ``mint`` function sends an amount of newly created coins to another address.
The :ref:`require <assert-and-require>` function call defines conditions that reverts all changes if not met.
In this example, ``require(msg.sender == minter);`` ensures that only the creator of the contract can call ``mint``,
and ``require(amount < 1e60);`` ensures a maximum amount of tokens. This ensures that there are no overflow errors in the future.
The ``mint`` function sends an amount of newly created coins to another address. The :ref:`require
<assert-and-require>` function call defines conditions that reverts all changes if not met. In this
example, ``require(msg.sender == minter);`` ensures that only the creator of the contract can call
``mint``. In general, the creator can mint as many tokens as they like, but at some point, this will
lead to a phenomenon called "overflow". Note that because of the default :ref:`Checked arithmetic
<unchecked>`, the transaction would revert if the expression ``balances[receiver] += amount;``
overflows, i.e., when ``balances[receiver] + amount`` in arbitrary precision arithmetic is larger
than the maximum value of ``uint`` (``2**256 - 1``). This is also true for the statement
``balances[receiver] += amount;`` in the function ``send``.
:ref:`Errors <errors>` allow you to provide more information to the caller about
why a condition or operation failed. Errors are used together with the