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| -rw-r--r-- | docs/control-structures.rst | 27 | ||||
| -rw-r--r-- | docs/frequently-asked-questions.rst | 25 |
2 files changed, 20 insertions, 32 deletions
diff --git a/docs/control-structures.rst b/docs/control-structures.rst index 9da29d14..5e3b722b 100644 --- a/docs/control-structures.rst +++ b/docs/control-structures.rst @@ -2,7 +2,7 @@ Expressions and Control Structures ################################## -.. index:: ! parameter, parameter;input, parameter;output +.. index:: ! parameter, parameter;input, parameter;output, parameter;multiple Input Parameters and Output Parameters ====================================== @@ -32,6 +32,8 @@ something like:: Input parameters can be used just as any other local variable can be used, they can also be assigned to. +.. index:: return array, return string, array, string, array of strings, dynamic array, variably sized array, return struct, struct + Output Parameters ----------------- @@ -54,12 +56,21 @@ write:: } The names of output parameters can be omitted. -The output values can also be specified using ``return`` statements, +The return values can be specified using ``return`` statements, which are also capable of :ref:`returning multiple values<multi-return>`. Return parameters can be used as any other local variable and they are zero-initialized; if they are not explicitly set, they stay zero. + +.. note:: + You cannot return some types from non-internal functions, notably + multi-dimensional dynamic arrays and structs. If you enable the + new experimental ``ABIEncoderV2`` feature by adding ``pragma experimental + ABIEncoderV2;`` to your source file then more types are available, but + ``mapping`` types are still limited to inside a single contract and you + cannot transfer them. + .. index:: if, else, while, do/while, for, break, continue, return, switch, goto Control Structures @@ -120,8 +131,8 @@ External Function Calls The expressions ``this.g(8);`` and ``c.g(2);`` (where ``c`` is a contract instance) are also valid function calls, but this time, the function will be called "externally", via a message call and not directly via jumps. -Please note that function calls on ``this`` cannot be used in the constructor, as the -actual contract has not been created yet. +Please note that function calls on ``this`` cannot be used in the constructor, +as the actual contract has not been created yet. Functions of other contracts have to be called externally. For an external call, all function arguments have to be copied to memory. @@ -130,8 +141,10 @@ all function arguments have to be copied to memory. A function call from one contract to another does not create its own transaction, it is a message call as part of the overall transaction. -When calling functions of other contracts, the amount of Wei sent with the call and -the gas can be specified with special options ``.value()`` and ``.gas()``, respectively:: +When calling functions of other contracts, you can specify the amount of Wei or gas sent with the call with the special options ``.value()`` and ``.gas()``, respectively. Any Wei you send to the contract is added to the total balance of the contract: + + +:: pragma solidity >=0.4.0 <0.6.0; @@ -400,7 +413,7 @@ In any case, you will get a warning about the outer variable being shadowed. } } -.. index:: ! exception, ! throw, ! assert, ! require, ! revert +.. index:: ! exception, ! throw, ! assert, ! require, ! revert, ! errors .. _assert-and-require: diff --git a/docs/frequently-asked-questions.rst b/docs/frequently-asked-questions.rst index 3e9a6aca..8b655b0d 100644 --- a/docs/frequently-asked-questions.rst +++ b/docs/frequently-asked-questions.rst @@ -38,11 +38,6 @@ has it (which includes `Remix <https://remix.ethereum.org/>`_), then ``contractname.kill.sendTransaction({from:eth.coinbase})``, just the same as my examples. -Can you return an array or a ``string`` from a solidity function call? -====================================================================== - -Yes. See `array_receiver_and_returner.sol <https://github.com/fivedogit/solidity-baby-steps/blob/master/contracts/60_array_receiver_and_returner.sol>`_. - Is it possible to in-line initialize an array like so: ``string[] myarray = ["a", "b"];`` ========================================================================================= @@ -61,11 +56,6 @@ Example:: } } -Can a contract function return a ``struct``? -============================================ - -Yes, but only in ``internal`` function calls or if ``pragma experimental "ABIEncoderV2";`` is used. - If I return an ``enum``, I only get integer values in web3.js. How to get the named values? =========================================================================================== @@ -103,15 +93,6 @@ How do structs work? See `struct_and_for_loop_tester.sol <https://github.com/fivedogit/solidity-baby-steps/blob/master/contracts/65_struct_and_for_loop_tester.sol>`_. -How do for loops work? -====================== - -Very similar to JavaScript. Such as the following example: - -``for (uint i = 0; i < a.length; i ++) { a[i] = i; }`` - -See `struct_and_for_loop_tester.sol <https://github.com/fivedogit/solidity-baby-steps/blob/master/contracts/65_struct_and_for_loop_tester.sol>`_. - What are some examples of basic string manipulation (``substring``, ``indexOf``, ``charAt``, etc)? ================================================================================================== @@ -292,12 +273,6 @@ In this example:: } } -Can a contract function accept a two-dimensional array? -======================================================= - -If you want to pass two-dimensional arrays across non-internal functions, -you most likely need to use ``pragma experimental "ABIEncoderV2";``. - What is the relationship between ``bytes32`` and ``string``? Why is it that ``bytes32 somevar = "stringliteral";`` works and what does the saved 32-byte hex value mean? ======================================================================================================================================================================== |