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? ? ?在學習 Erlang 過程中，經常會遇到以下兩個和比較相關的操作：match 和 compare equal ?，F作如下解釋：
? ? ?當兩個 Erlang term 擁有完全相同類型和值時，我們稱它們 match 。例如：1 match 1 為 true ，但 1 match 1.0 為 false 。
? ? ?當兩個 Erlang term?擁有完全相同類型和值時，或者兩者均為數值類型，且可以延伸為相同的值時，我們稱它們 compare equal 。例如，1 compare equal 1 為 true，且 1 compare equal 1.0 為 true 。

另外一個比較直觀的說法是：

The difference being the same as between =:= and ==. 即 match 相當于 =:= ，而 ?compare equal 相當于 == 。
? ? ?在實際應用中，ETS 中 set 類型的表采用的是 match ，而 ordered_set 類型的表采用的是 compare equal。
原文參考：
Also worth noting is the subtle difference between matching and comparing equal, which is demonstrated by the different table types set and ordered_set. Two Erlang terms match if they are of the same type and have the same value, so that 1 matches 1, but not 1.0 (as 1.0 is a float() and not an integer()). Two Erlang terms compare equal if they either are of the same type and value, or if both are numeric types and extend to the same value, so that 1 compares equal to both 1 and 1.0. The ordered_set works on the Erlang term order and there is no defined order between an integer() and a float() that extends to the same value, hence the key 1 and the key 1.0 are regarded as equal in an ordered_set table.

轉載于:https://my.oschina.net/moooofly/blog/107925

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