constructor with default arguments

基本解釋

The variables at the right with no corresponding constructor arguments are default constructed.
右邊那些沒有對應(yīng)的構(gòu)造函數(shù)參數(shù)的變量將被默認(rèn)構(gòu)造。
However, there is one important difference between structures and classes: structures can have a default constructor (that is, one with no arguments) even if no primary constructor is defined.
但是，結(jié)構(gòu)和類之間有一個重要區(qū)別：結(jié)構(gòu)可以有默認(rèn)構(gòu)造函數(shù)（即，沒有參數(shù)的構(gòu)造函數(shù)），即使未定義主構(gòu)造函數(shù)也是如此。