precedencegroupTablePrecedence {
associativity: left
higherThan: LogicalConjunctionPrecedence
}
precedencegroupSectionPrecedence {
associativity: left
higherThan: TablePrecedence
}
infixoperator+++ : TablePrecedence
infixoperator<<< : SectionPrecedence
precedencegroup: 定义了一个操作符优先级别。操作符优先级的定义和类型声明有些相似，一个操作符比需要属于某个特定的优先级。
infix:表示要定义的是一个中位操作符，即前后都是输入.
prefix: 前置运算符.
postfix:后置运算符.
associativity :定义了结合律，即如果多个同类的操作符顺序出现的计算顺序。
higherThan: 运算的优先级，点积运算是优先于乘法运算的。
lowerThan:来指定优先级低于某个其他组。
分别声明关联性和优先级
associativity Multiplicative left
precedence Multiplicative>Additive
precedence Exponentiative>Multiplicative
precedence Multiplicative {
associativity(left)
precedence(> Additive)
precedence(< Exponentiative)
}
precedence Multiplicative {
associativity: left
precedence: higherThan(Additive)
precedence: lowerThan(Exponentiative)
}
precedence Multiplicative {
associativity(left)
higherThan(Additive)
lowerThan(Exponentiative)
}
precedence Multiplicative {
associativity: left,
higherThan: Additive,
lowerThan: Exponentiative
}
precedence Multiplicative {
associativity left
higherThan Additive
lowerThan Exponentiative
}
precedence Multiplicative {
associativity left
> Additive
< Exponentiative
}
precedence Multiplicative : associativity(left),
higherThan(Additive),
lowerThan(Exponentiative)
precedence Multiplicative : associativity left,
higherThan Additive, lowerThan Exponentiative
precedence Multiplicative > Additive,
< Exponentiative,
associativity left
precedence left Multiplicative > Additive,
< Exponentiative
precedence associativity(left) Multiplicative > Additive,
< Exponentiative
Swift 标准库中已经定义了一些常用的运算优先级组，比如加法优先级 (AdditionPrecedence) 和乘法优先级 (MultiplicationPrecedence) 等，你可以在这里找到完整的列表
Standard library changes
precedencegroupAssignmentPrecedence {
assignment: true
associativity: right
}
precedencegroupTernaryPrecedence {
associativity: right
higherThan: AssignmentPrecedence
}
precedencegroupDefaultPrecedence {
higherThan: TernaryPrecedence
}
precedencegroupLogicalDisjunctionPrecedence {
associativity: left
higherThan: TernaryPrecedence
}
precedencegroupLogicalConjunctionPrecedence {
associativity: left
higherThan: LogicalDisjunctionPrecedence
}
precedencegroupComparisonPrecedence {
higherThan: LogicalConjunctionPrecedence
}
precedencegroupNilCoalescingPrecedence {
associativity: right
higherThan: ComparisonPrecedence
}
precedencegroupCastingPrecedence {
higherThan: NilCoalescingPrecedence
}
precedencegroupRangeFormationPrecedence {
higherThan: CastingPrecedence
}
precedencegroupAdditionPrecedence {
associativity: left
higherThan: RangeFormationPrecedence
}
precedencegroupMultiplicationPrecedence {
associativity: left
higherThan: AdditionPrecedence
}
precedencegroupBitwiseShiftPrecedence {
higherThan: MultiplicationPrecedence
}
postfix operator ++
postfix operator --
// postfix operator !
prefix operator ++
prefix operator --
prefix operator !
prefix operator ~
prefix operator +
prefix operator -
// infix operator = : AssignmentPrecedence
infixoperator*= : AssignmentPrecedence
infixoperator/= : AssignmentPrecedence
infixoperator%= : AssignmentPrecedence
infixoperator+= : AssignmentPrecedence
infixoperator-= : AssignmentPrecedence
infixoperator<<= : AssignmentPrecedence
infixoperator>>= : AssignmentPrecedence
infixoperator&= : AssignmentPrecedence
infixoperator^= : AssignmentPrecedence
infixoperator|= : AssignmentPrecedence
// infix operator ?: : TernaryPrecedence
infixoperator|| : LogicalDisjunctionPrecedence
infixoperator&& : LogicalConjunctionPrecedence
infixoperator< : ComparisonPrecedence
infixoperator<= : ComparisonPrecedence
infixoperator> : ComparisonPrecedence
infixoperator>= : ComparisonPrecedence
infixoperator== : ComparisonPrecedence
infixoperator!= : ComparisonPrecedence
infixoperator=== : ComparisonPrecedence
infixoperator!== : ComparisonPrecedence
infixoperator~= : ComparisonPrecedence
infixoperator?? : NilCoalescingPrecedence
// infix operator as : CastingPrecedence
// infix operator as? : CastingPrecedence
// infix operator as! : CastingPrecedence
// infix operator is : CastingPrecedence
infixoperator..< : RangeFormationPrecedence
infixoperator... : RangeFormationPrecedence
infixoperator+ : AdditionPrecedence
infixoperator- : AdditionPrecedence
infixoperator&+ : AdditionPrecedence
infixoperator&- : AdditionPrecedence
infixoperator| : AdditionPrecedence
infixoperator^ : AdditionPrecedence
infixoperator* : MultiplicationPrecedence
infixoperator/ : MultiplicationPrecedence
infixoperator% : MultiplicationPrecedence
infixoperator&* : MultiplicationPrecedence
infixoperator& : MultiplicationPrecedence
infixoperator<< : BitwiseShiftPrecedence
infixoperator>> : BitwiseShiftPrecedence