comparison

问题 I got a very awkward and specific issue with a simplexml evaluation. The code: $simplexml = simplexml_load_string($xmlstring); var_dump($simplexml); var_dump($simplexml == false); //this comparison var_dump($simplexml) returns the actual structure of my simplexml but the comparison returns 'true' for this specific simplexml, which I can't show the structure because of my contract. I'm sure that's very specifc issue 'cause I tried other XML strings and the comparison returns 'false'.

问题 I got a very awkward and specific issue with a simplexml evaluation. The code: $simplexml = simplexml_load_string($xmlstring); var_dump($simplexml); var_dump($simplexml == false); //this comparison var_dump($simplexml) returns the actual structure of my simplexml but the comparison returns 'true' for this specific simplexml, which I can't show the structure because of my contract. I'm sure that's very specifc issue 'cause I tried other XML strings and the comparison returns 'false'.

问题 How do I achieve the effect of the === operator in Python? For example, I don't want False == 0 to be True . 回答1: Try variable is False . False is 0 returns False , 回答2: If you want to check that the value and type are the same use: x == y and type(x) == type(y) In Python, explicit type comparisons like this are usually avoided, but because booleans are a subclass of integers it's the only choice here. x is y compares identity—whether two names refer to the same object in memory. The Python

问题 Do unions have a control structure to test which member is currently in use (or if it has any at all)? I'm asking this because undefined behavior is never a good thing to have in your program. 回答1: No, no such mechanism exists off-the-shelf. You'll have to take care of that yourself. The usual approach is wrapping the union in a struct : struct MyUnion { int whichMember; union { //whatever } actualUnion; }; So you have MyUnion x; and x.whichMember tells you which field of x.actualUnion is in

问题 I was under the impression that = is an assignment, == is a numeric comparison, and === is a symbolic comparison (as well as in some other languages == being equal to and === being identical to . However, looking at the following it would appear that this is not necessarily the case... In: x == x Out: True In: x === x Out: True In: 5 == 5 Out: True In: 5 === 5 Out: True In: x = 5 Out: 5 In: 5 == x Out: True In: 5 === x Out: True In: 5 5 == 5x Out: True In: 5 5 === 5x Out: True In: x == y Out:

问题 To check for overlap in two different dateranges, {Start1, End1} and {Start2, End2} I am checking: if ((Start1 <= End2) && (End1 >= Start2)) { //overlap exists } The question is, what is a good way to compare overlaps if I had let's say five dateranges? . checking to see if any of them don't overlap each other? If I have multiple date ranges, how to find if any of these ranges are overlapping? 回答1: To find if all are overlapping static bool Overlap(params Tuple<DateTime, DateTime>[] ranges) {

问题 Given n numbers, how do I find the largest and second largest number using at most n+log(n) comparisons? Note that it's not O(n+log(n)), but really n+log(n) comparisons. 回答1: pajton gave a comment. Let me elaborate. As pajton said, this can be done by tournament selection. Think of this as a knock out singles tennis tournament, where player abilities have a strict order and the outcome of a match is decided solely by that order. In the first round half the people are eliminated. In the next

问题 Given n numbers, how do I find the largest and second largest number using at most n+log(n) comparisons? Note that it's not O(n+log(n)), but really n+log(n) comparisons. 回答1: pajton gave a comment. Let me elaborate. As pajton said, this can be done by tournament selection. Think of this as a knock out singles tennis tournament, where player abilities have a strict order and the outcome of a match is decided solely by that order. In the first round half the people are eliminated. In the next

问题 Given n numbers, how do I find the largest and second largest number using at most n+log(n) comparisons? Note that it's not O(n+log(n)), but really n+log(n) comparisons. 回答1: pajton gave a comment. Let me elaborate. As pajton said, this can be done by tournament selection. Think of this as a knock out singles tennis tournament, where player abilities have a strict order and the outcome of a match is decided solely by that order. In the first round half the people are eliminated. In the next

问题 TL;DR: How can you compare two python dictionaries if some of them have values which are unhashable/mutable (e.g. lists or pandas Dataframes)? I have to compare dictionary pairs for equality. In that sense, this question is similar to these two, but their solutions only seem to work for immutable objects ... Is there a better way to compare dictionary values Comparing two dictionaries in Python My problem, is that I'm dealing with pairs of highly nested dictionaries where the unhashable