associativity

Does it make sense for unary operators to be associative?

由 左心房为你撑大大i 提交于 2019-11-26 21:47:12
问题 The C++ operator precedence table from http://en.cppreference.com/w/cpp/language/operator_precedence (I know it's not normative, but the standard doesn't talk about precedence or associativity) marks unary operators as right/left associative. From a discussion on a different question, I'm left with doubts. Does it make sense for unary operators to be associative? 回答1: It's just an artefact of the way that the associativity is derived from the grammar. The reason that addition is left

Ternary operator left associativity

由 拥有回忆 提交于 2019-11-26 20:20:42
In the PHP manual, I find the following 'user contributed note' under "Operators". Note that in php the ternary operator ?: has a left associativity unlike in C and C++ where it has right associativity. You cannot write code like this (as you may have accustomed to in C/C++): <?php $a = 2; echo ( $a == 1 ? 'one' : $a == 2 ? 'two' : $a == 3 ? 'three' : $a == 4 ? 'four' : 'other'); echo "\n"; // prints 'four' I actually try it and it really prints four . However I could not understand the reason behind it and still feel it should print two or other . Can someone please explain what is happening

Python comparison operators chaining/grouping left to right?

由 删除回忆录丶 提交于 2019-11-26 19:01:40
The Python documentation for operator precedence states: Operators in the same box group left to right (except for comparisons, including tests, which all have the same precedence and chain from left to right — see section Comparisons ...) What does this mean? Specifically: "Operators in the same box group left to right (except for comparisons...)" -- do comparisons not group left to right? If comparisons do not group left to right, what do they do instead? Do they "chain" as opposed to "group"? If comparisons "chain" rather than "group", what is the difference between "chaining" and "grouping

C# conditional AND (&&) OR (||) precedence

由 守給你的承諾、 提交于 2019-11-26 09:29:32
问题 We get into unnecessary coding arguments at my work all-the-time. Today I asked if conditional AND (&&) or OR (||) had higher precedence. One of my coworkers insisted that they had the same precedence, I had doubts, so I looked it up. According to MSDN AND (&&) has higher precedence than OR (||). But, can you prove it to a skeptical coworker? http://msdn.microsoft.com/en-us/library/aa691323(VS.71).aspx bool result = false || true && false; // --> false // is the same result as bool result =

Python comparison operators chaining/grouping left to right?

由 ￡可爱￡侵袭症＋ 提交于 2019-11-26 05:37:06
问题 The Python documentation for operator precedence states: Operators in the same box group left to right (except for comparisons, including tests, which all have the same precedence and chain from left to right — see section Comparisons...) What does this mean? Specifically: \"Operators in the same box group left to right (except for comparisons...)\" -- do comparisons not group left to right? If comparisons do not group left to right, what do they do instead? Do they \"chain\" as opposed to \
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