在Swift 2.1中,可以编译以下代码.
let a = [1: [1]]
a == [1: [1]]
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但是,以下代码无法编译.
let a = [1: [1]]
let b = [1: [1]]
a == b // => binary operator '==' cannot be applied to two '[Int : Array<Int>]' operands
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怎么理解这种行为?