2.8. Functions#

Syntax#

FunctionDefinition = (* function_keyword: *) FUNCTION_KEYWORD
                     (* name: *) FunctionName
                     (* parameters: *) ParametersDeclaration
                     (* attributes: *) FunctionAttributes
                     (* returns: *) ReturnsDeclaration?
                     (* body: *) FunctionBody;

FunctionName = (* variant: *) IDENTIFIER
             | (* variant: *) FALLBACK_KEYWORD
             | (* variant: *) RECEIVE_KEYWORD;

ParametersDeclaration = (* open_paren: *) OPEN_PAREN
                        (* parameters: *) Parameters
                        (* close_paren: *) CLOSE_PAREN;

Parameters = ((* item: *) Parameter ((* separator: *) COMMA (* item: *) Parameter)*)?;

Parameter = (* type_name: *) TypeName
            (* storage_location: *) StorageLocation?
            (* name: *) IDENTIFIER?;

FunctionAttributes = (* item: *) FunctionAttribute*;

FunctionAttribute = (* variant: *) ModifierInvocation
                  | (* variant: *) OverrideSpecifier (* Introduced in 0.6.0 *)
                  | (* variant: *) CONSTANT_KEYWORD (* Deprecated in 0.5.0 *)
                  | (* variant: *) EXTERNAL_KEYWORD
                  | (* variant: *) INTERNAL_KEYWORD
                  | (* variant: *) PAYABLE_KEYWORD
                  | (* variant: *) PRIVATE_KEYWORD
                  | (* variant: *) PUBLIC_KEYWORD
                  | (* variant: *) PURE_KEYWORD (* Introduced in 0.4.16 *)
                  | (* variant: *) VIEW_KEYWORD (* Introduced in 0.4.16 *)
                  | (* variant: *) VIRTUAL_KEYWORD; (* Introduced in 0.6.0 *)

(* Introduced in 0.6.0 *)
OverrideSpecifier = (* override_keyword: *) OVERRIDE_KEYWORD
                    (* overridden: *) OverridePathsDeclaration?;

(* Introduced in 0.6.0 *)
OverridePathsDeclaration = (* open_paren: *) OPEN_PAREN
                           (* paths: *) OverridePaths
                           (* close_paren: *) CLOSE_PAREN;

(* Introduced in 0.6.0 *)
OverridePaths = (* item: *) IdentifierPath ((* separator: *) COMMA (* item: *) IdentifierPath)*;

ReturnsDeclaration = (* returns_keyword: *) RETURNS_KEYWORD
                     (* variables: *) ParametersDeclaration;

FunctionBody = (* variant: *) Block
             | (* variant: *) SEMICOLON;

(* Introduced in 0.4.22 *)
ConstructorDefinition = (* constructor_keyword: *) CONSTRUCTOR_KEYWORD
                        (* parameters: *) ParametersDeclaration
                        (* attributes: *) ConstructorAttributes
                        (* body: *) Block;

(* Introduced in 0.4.22 *)
ConstructorAttributes = (* item: *) ConstructorAttribute*;

(* Introduced in 0.4.22 *)
ConstructorAttribute = (* variant: *) ModifierInvocation
                     | (* variant: *) INTERNAL_KEYWORD
                     | (* variant: *) OVERRIDE_KEYWORD (* Introduced in 0.6.0 and deprecated in 0.6.7. *)
                     | (* variant: *) PAYABLE_KEYWORD
                     | (* variant: *) PUBLIC_KEYWORD
                     | (* variant: *) VIRTUAL_KEYWORD; (* Introduced in 0.6.0 and deprecated in 0.6.7. *)

(* Deprecated in 0.6.0 *)
UnnamedFunctionDefinition = (* function_keyword: *) FUNCTION_KEYWORD
                            (* parameters: *) ParametersDeclaration
                            (* attributes: *) UnnamedFunctionAttributes
                            (* body: *) FunctionBody;

(* Deprecated in 0.6.0 *)
UnnamedFunctionAttributes = (* item: *) UnnamedFunctionAttribute*;

(* Deprecated in 0.6.0 *)
UnnamedFunctionAttribute = (* variant: *) ModifierInvocation
                         | (* variant: *) CONSTANT_KEYWORD (* Deprecated in 0.5.0 *)
                         | (* variant: *) EXTERNAL_KEYWORD
                         | (* variant: *) INTERNAL_KEYWORD (* Deprecated in 0.5.0 *)
                         | (* variant: *) PAYABLE_KEYWORD
                         | (* variant: *) PRIVATE_KEYWORD (* Deprecated in 0.5.0 *)
                         | (* variant: *) PUBLIC_KEYWORD (* Deprecated in 0.5.0 *)
                         | (* variant: *) PURE_KEYWORD (* Introduced in 0.4.16 and deprecated in 0.6.0. *)
                         | (* variant: *) VIEW_KEYWORD; (* Introduced in 0.4.16 and deprecated in 0.6.0. *)

(* Introduced in 0.6.0 *)
FallbackFunctionDefinition = (* fallback_keyword: *) FALLBACK_KEYWORD
                             (* parameters: *) ParametersDeclaration
                             (* attributes: *) FallbackFunctionAttributes
                             (* returns: *) ReturnsDeclaration?
                             (* body: *) FunctionBody;

(* Introduced in 0.6.0 *)
FallbackFunctionAttributes = (* item: *) FallbackFunctionAttribute*;

(* Introduced in 0.6.0 *)
FallbackFunctionAttribute = (* variant: *) ModifierInvocation
                          | (* variant: *) OverrideSpecifier
                          | (* variant: *) EXTERNAL_KEYWORD
                          | (* variant: *) PAYABLE_KEYWORD
                          | (* variant: *) PURE_KEYWORD
                          | (* variant: *) VIEW_KEYWORD
                          | (* variant: *) VIRTUAL_KEYWORD;

(* Introduced in 0.6.0 *)
ReceiveFunctionDefinition = (* receive_keyword: *) RECEIVE_KEYWORD
                            (* parameters: *) ParametersDeclaration
                            (* attributes: *) ReceiveFunctionAttributes
                            (* body: *) FunctionBody;

(* Introduced in 0.6.0 *)
ReceiveFunctionAttributes = (* item: *) ReceiveFunctionAttribute*;

(* Introduced in 0.6.0 *)
ReceiveFunctionAttribute = (* variant: *) ModifierInvocation
                         | (* variant: *) OverrideSpecifier
                         | (* variant: *) EXTERNAL_KEYWORD
                         | (* variant: *) PAYABLE_KEYWORD
                         | (* variant: *) VIRTUAL_KEYWORD;

Function Definitions#

Functions are the executable units of code. Functions are usually defined inside a contract, but they can also be defined outside of contracts.

contract MyContract {
    function contractFunction() public {
        // Inside the contract
    }
}

function helperFunction() {
    // Outside the contract
}

Functions can be overloaded, where multiple functions with the same name, but with different parameters, can co-exist.