From 741ada79f9fd58a3b652cf42de2a69cad54070b0 Mon Sep 17 00:00:00 2001 From: chriseth Date: Fri, 4 May 2018 16:27:21 +0200 Subject: Update documentation. --- docs/control-structures.rst | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'docs/control-structures.rst') diff --git a/docs/control-structures.rst b/docs/control-structures.rst index f3c351dd..f18e1e10 100644 --- a/docs/control-structures.rst +++ b/docs/control-structures.rst @@ -293,12 +293,7 @@ Solidity internally allows tuple types, i.e. a list of objects of potentially di // Common trick to swap values -- does not work for non-value storage types. (x, y) = (y, x); // Components can be left out (also for variable declarations). - // If the tuple ends in an empty component, - // the rest of the values are discarded. - (data.length,) = f(); // Sets the length to 7 - // The same can be done on the left side. - // If the tuple begins in an empty component, the beginning values are discarded. - (,data[3]) = f(); // Sets data[3] to 2 + (data.length,,) = f(); // Sets the length to 7 // Components can only be left out at the left-hand-side of assignments, with // one exception: (x,) = (1,); @@ -307,6 +302,11 @@ Solidity internally allows tuple types, i.e. a list of objects of potentially di } } +.. note:: + Prior to version 0.4.24 it was possible to assign to tuples of smaller size, either + filling up on the left or on the right side (which ever was empty). This is + now deprecated, both sides have to have the same number of components. + Complications for Arrays and Structs ------------------------------------ -- cgit v1.2.3 From 6c8f78fb8ff99c5d28669fa7383a25b8c8523915 Mon Sep 17 00:00:00 2001 From: chriseth Date: Mon, 30 Apr 2018 13:30:09 +0200 Subject: Update documentation for multi variable declaration statement. --- docs/control-structures.rst | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) (limited to 'docs/control-structures.rst') diff --git a/docs/control-structures.rst b/docs/control-structures.rst index f18e1e10..7849d15a 100644 --- a/docs/control-structures.rst +++ b/docs/control-structures.rst @@ -272,9 +272,12 @@ Assignment Destructuring Assignments and Returning Multiple Values ------------------------------------------------------- -Solidity internally allows tuple types, i.e. a list of objects of potentially different types whose size is a constant at compile-time. Those tuples can be used to return multiple values at the same time and also assign them to multiple variables (or LValues in general) at the same time:: +Solidity internally allows tuple types, i.e. a list of objects of potentially different types whose size is a constant at compile-time. Those tuples can be used to return multiple values at the same time. +These can then either be assigned to newly declared variables or to pre-existing variables (or LValues in general): - pragma solidity ^0.4.16; +:: + + pragma solidity >0.4.23 <0.5.0; contract C { uint[] data; @@ -284,12 +287,8 @@ Solidity internally allows tuple types, i.e. a list of objects of potentially di } function g() public { - // Variables declared with type - uint x; - bool b; - uint y; - // Tuple values can be assigned to these pre-existing variables - (x, b, y) = f(); + // Variables declared with type and assigned from the returned tuple. + (uint x, bool b, uint y) = f(); // Common trick to swap values -- does not work for non-value storage types. (x, y) = (y, x); // Components can be left out (also for variable declarations). @@ -330,7 +329,9 @@ A variable declared anywhere within a function will be in scope for the *entire (this will change soon, see below). This happens because Solidity inherits its scoping rules from JavaScript. This is in contrast to many languages where variables are only scoped where they are declared until the end of the semantic block. -As a result, the following code is illegal and cause the compiler to throw an error, ``Identifier already declared``:: +As a result, the following code is illegal and cause the compiler to throw an error, ``Identifier already declared``: + +:: // This will not compile -- cgit v1.2.3