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Added section on address-related constants

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Denton Liu 2016-05-25 10:44:35 -04:00
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docs/units-and-global-variables.rst
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@ -111,6 +111,21 @@ same as ``sha3(uint16(0x12))``.
It might be that you run into Out-of-Gas for ``sha256``, ``ripemd160`` or ``ecrecover`` on a *private blockchain*. The reason for this is that those are implemented as so-called precompiled contracts and these contracts only really exist after they received the first message (although their contract code is hardcoded). Messages to non-existing contracts are more expensive and thus the execution runs into an Out-of-Gas error. A workaround for this problem is to first send e.g. 1 Wei to each of the contracts before you use them in your actual contracts. This is not an issue on the official or test net. It might be that you run into Out-of-Gas for ``sha256``, ``ripemd160`` or ``ecrecover`` on a *private blockchain*. The reason for this is that those are implemented as so-called precompiled contracts and these contracts only really exist after they received the first message (although their contract code is hardcoded). Messages to non-existing contracts are more expensive and thus the execution runs into an Out-of-Gas error. A workaround for this problem is to first send e.g. 1 Wei to each of the contracts before you use them in your actual contracts. This is not an issue on the official or test net.
.. index:: send, balance
Address Related
---------------
``<address>.balance`` (``uint256``):
balance of the address in Wei
``<address>.send(uint256) returns (bool)``:
send given amount of Wei to address, returns ``false`` on failure
.. warning::
Since it is possible for calls to ``send`` to fail, such as
if there are insufficient funds, it is good practice to
check the return value whenever calling ``send``.
.. index:: this, selfdestruct .. index:: this, selfdestruct
Contract Related Contract Related