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| -rw-r--r-- | docs/control-structures.rst | 80 |
1 files changed, 49 insertions, 31 deletions
diff --git a/docs/control-structures.rst b/docs/control-structures.rst index 5e3b722b..889fbdb9 100644 --- a/docs/control-structures.rst +++ b/docs/control-structures.rst @@ -2,23 +2,22 @@ Expressions and Control Structures ################################## -.. index:: ! parameter, parameter;input, parameter;output, parameter;multiple +.. index:: ! parameter, parameter;input, parameter;output, function parameter, parameter;function, return variable, variable;return, return -Input Parameters and Output Parameters -====================================== +Function Parameters and Return Variables +======================================== -As in Javascript, functions may take parameters as input; -unlike in Javascript and C, they may also return arbitrary number of -parameters as output. +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. -Input Parameters ----------------- +Function Parameters +------------------- + +Function parameters are declared the same way as variables, and the name of +unused parameters can be omitted. -The input parameters are declared the same way as variables are. -The name of unused parameters can be omitted. -For example, suppose we want our contract to -accept one kind of external calls with two integers, we would write -something like:: +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; @@ -29,18 +28,18 @@ something like:: } } -Input parameters can be used just as any other local variable -can be used, they can also be assigned to. +Function parameters can be used as any other local variable and 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 ------------------ +Return Variables +---------------- -The output parameters can be declared with the same syntax after the -``returns`` keyword. For example, suppose we wished to return two results: -the sum and the product of the two given integers, then we would -write:: +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; @@ -55,12 +54,31 @@ write:: } } -The names of output parameters can be omitted. -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. +The names of return variables can be omitted. +Return variables can be used as any other local variable and they +are zero-initialized. If they are not explicitly +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:: @@ -90,12 +108,12 @@ Solidity. .. _multi-return: -Returning Multiple Values -------------------------- +Returning Multiple Variables +---------------------------- -When a function has multiple output parameters, ``return (v0, v1, ..., +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 output parameters. +the same as the number of return types. .. index:: ! function;call, function;internal, function;external |