ContractDefinition = 'contract' Identifier '{' ContractPart* '}'
ContractPart = VariableDeclaration ';' | StructDefinition ';' |
               FunctionDefinition ';' | 'public:' | 'private:'

StructDefinition = 'struct' Identifier '{'
                     ( VariableDeclaration (';' VariableDeclaration)* )? '}

FunctionDefinition = 'function' Identifier ArgumentList 'const'?
                     'returns' ArgumentList Block
ArgumentList = '(' ( VariableDeclaration (',' VariableDeclaration)* )? ')'
// semantic restriction: mappings and structs (recursively) containing mappings
// are not allowed in argument lists
VariableDeclaration = TypeName Identifier
TypeName = PredefinedType | Identifier | MappingType
MappingType = 'mapping' '(' SimplePredefinedType '=>' TypeName ')'

Block = '{' Statement* '}'
Statement = IfStatement | WhileStatement | Continue | Break | Return | VariableAssignment | Expression ';' | Block

IfStatement = 'if' '(' Expression ')' Statement ( 'else' Statement )?
WhileStatement = 'while' '(' Expression ')' Statement
Continue = 'continue' ';'
Break = 'break' ';'
Return = 'return' Expression? ';'
VariableAssignment = VariableDeclaration ( AssignmentOp Expression )? ';'

Expression = Assignment | UnaryOperation | BinaryOperation | FunctionCall | IndexAccess | MemberAccess | PrimaryExpression
Assignment = Expression (AssignmentOp Expression)
FunctionCall = Identifier '(' ( Expression ( ',' Expression )* ) ')'
MemberAccess = Expression '.' Identifier
IndexAccess = Expression '[' Expresison ']'
PrimaryExpression = Identifier | NumberLiteral | StringLiteral | '(' Expression ')'