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| -rw-r--r-- | docs/contracts.rst | 102 | ||||
| -rw-r--r-- | docs/control-structures.rst | 103 |
2 files changed, 102 insertions, 103 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index c1c51e56..9913cfb3 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -485,6 +485,108 @@ value types and strings. Functions ********* +Function Parameters and Return Variables +======================================== + +As in JavaScript, functions may take parameters as input. Unlike in JavaScript +and C, functions may also return an arbitrary number of values as output. + +Function Parameters +------------------- + +Function parameters are declared the same way as variables, and the name of +unused parameters can be omitted. + +For example, if you want your contract to accept one kind of external call +with two integers, you would use something like:: + + pragma solidity >=0.4.16 <0.6.0; + + contract Simple { + uint sum; + function taker(uint _a, uint _b) public { + sum = _a + _b; + } + } + +Function parameters can be used as any other local variable and they can also be assigned to. + +.. note:: + + An :ref:`external function<external-function-calls>` cannot accept a + multi-dimensional array as an input + parameter. This functionality is possible if you enable the new + experimental ``ABIEncoderV2`` feature by adding ``pragma experimental ABIEncoderV2;`` to your source file. + + An :ref:`internal function<external-function-calls>` can accept a + multi-dimensional array without enabling the feature. + +.. index:: return array, return string, array, string, array of strings, dynamic array, variably sized array, return struct, struct + +Return Variables +---------------- + +Function return variables are declared with the same syntax after the +``returns`` keyword. + +For example, suppose you want to return two results: the sum and the product of +two integers passed as function parameters, then you use something like:: + + pragma solidity >=0.4.16 <0.6.0; + + contract Simple { + function arithmetic(uint _a, uint _b) + public + pure + returns (uint o_sum, uint o_product) + { + o_sum = _a + _b; + o_product = _a * _b; + } + } + +The names of return variables can be omitted. +Return variables can be used as any other local variable and they +are initialized with their :ref:`default value <default-value>` and have that value unless explicitly set. + +You can either explicitly assign to return variables and +then leave the function using ``return;``, +or you can provide return values +(either a single or :ref:`multiple ones<multi-return>`) directly with the ``return`` +statement:: + + pragma solidity >=0.4.16 <0.6.0; + + contract Simple { + function arithmetic(uint _a, uint _b) + public + pure + returns (uint o_sum, uint o_product) + { + return (_a + _b, _a * _b); + } + } + +This form is equivalent to first assigning values to the +return variables and then using ``return;`` to leave the function. + +.. 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. + +.. _multi-return: + +Returning Multiple Values +------------------------- + +When a function has multiple return types, the statement ``return (v0, v1, ..., vn) can be used to return multiple values. +vn)`` can return multiple values. The number of components must be +the same as the number of return types. + .. index:: ! view function, function;view .. _view-functions: diff --git a/docs/control-structures.rst b/docs/control-structures.rst index 720b7084..f8016806 100644 --- a/docs/control-structures.rst +++ b/docs/control-structures.rst @@ -4,100 +4,6 @@ Expressions and Control Structures .. index:: ! parameter, parameter;input, parameter;output, function parameter, parameter;function, return variable, variable;return, return -Function Parameters and Return Variables -======================================== - -As in JavaScript, functions may take parameters as input. Unlike in JavaScript -and C, functions may also return an arbitrary number of values as output. - -Function Parameters -------------------- - -Function parameters are declared the same way as variables, and the name of -unused parameters can be omitted. - -For example, if you want your contract to accept one kind of external call -with two integers, you would use something like:: - - pragma solidity >=0.4.16 <0.6.0; - - contract Simple { - uint sum; - function taker(uint _a, uint _b) public { - sum = _a + _b; - } - } - -Function parameters can be used as any other local variable and they can also be assigned to. - -.. note:: - - An :ref:`external function<external-function-calls>` cannot accept a - multi-dimensional array as an input - parameter. This functionality is possible if you enable the new - experimental ``ABIEncoderV2`` feature by adding ``pragma experimental ABIEncoderV2;`` to your source file. - - An :ref:`internal function<external-function-calls>` can accept a - multi-dimensional array without enabling the feature. - -.. index:: return array, return string, array, string, array of strings, dynamic array, variably sized array, return struct, struct - -Return Variables ----------------- - -Function return variables are declared with the same syntax after the -``returns`` keyword. - -For example, suppose you want to return two results: the sum and the product of -two integers passed as function parameters, then you use something like:: - - pragma solidity >=0.4.16 <0.6.0; - - contract Simple { - function arithmetic(uint _a, uint _b) - public - pure - returns (uint o_sum, uint o_product) - { - o_sum = _a + _b; - o_product = _a * _b; - } - } - -The names of return variables can be omitted. -Return variables can be used as any other local variable and they -are initialized with their :ref:`default value <default-value>` and have that value unless explicitly set. -set, they stay zero value. - -You can either explicitly assign to return variables and -then leave the function using ``return;``, -or you can provide return values -(either a single or :ref:`multiple ones<multi-return>`) directly with the ``return`` -statement:: - - pragma solidity >=0.4.16 <0.6.0; - - contract Simple { - function arithmetic(uint _a, uint _b) - public - pure - returns (uint o_sum, uint o_product) - { - return (_a + _b, _a * _b); - } - } - -This form is equivalent to first assigning values to the -return variables and then using ``return;`` to leave the function. - - -.. 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 @@ -116,15 +22,6 @@ Note that there is no type conversion from non-boolean to boolean types as there is in C and JavaScript, so ``if (1) { ... }`` is *not* valid Solidity. -.. _multi-return: - -Returning Multiple Variables ----------------------------- - -When a function has multiple return types, ``return (v0, v1, ..., -vn)`` can return multiple values. The number of components must be -the same as the number of return types. - .. index:: ! function;call, function;internal, function;external .. _function-calls: |