comparison

问题 SO, The problem It's not well-known, but PHP allows to compare objects - and not just on equality == - but on < and > too. But - how it works? So if I want to create comparable objects - what restrictions/rules they should follow? Most useful case is with DateTime() objects - they hold certain timestamp and they could be compared (and this has logical sense). On lxr there's some explanation for DateTime . But what about common case? I have: class C { protected $holder; protected $mirror;

问题 I am trying to compare to strings: Start Time: 10:00 End Time: 12:00 In actuality there is a start time array that contains my values and an end time array. In this case, it would be structured as such: StartTimes[0] = "10:00" EndTimes[0] = "12:00" What is the best way (using java) to find out the duration between the times. The start time will always be before the end time. Should I try to separate the string by minute and hour using regex, then parse the hour and parse the minute, compare,

问题 Is it feasible to test whether some dataframe is simply a sorted version of another dataframe? For example, if I have two dataframes a and b , is there some way to easily determine whether a is simply a reordered version of b (or vice versa)? Here's a trivial example: a <- data.frame(x1=1:10, x2=11:20, x3=1:2) b <- a[order(a$x3, a$x1, decreasing=TRUE),] The closest thing I can think of is all.equal , but its output is not helpful (to me, at least): > all.equal(a,b) [1] "Attributes: <

问题 I have a list of several vectors. I would like to check whether all vectors in the list are equal. There's identical which only works for pairwise comparison. So I wrote the following function which looks ugly to me. Still I did not find a better solution. Here's my RE: test_true <- list(a=c(1,2,3),b=c(1,2,3),d=c(1,2,3)) test_false <- list(a=c(1,2,3),b=c(1,2,3),d=c(1,32,13)) compareList <- function(li){ stopifnot(length(li) > 1) l <- length(li) res <- lapply(li[-1],function(X,x) identical(X,x

问题 Say I have this array: A, B 1, G 2, X 3, F 4, Z 5, I If column B equals [X, Y or Z] replace column A with value "T" I've found how to change values within the same column but not across, any help would be most appreciated. 回答1: You can try this: import pandas as pd df = pd.DataFrame({ 'A': [1, 2, 3, 4, 5], 'B': ['G', 'X', 'F', 'Z', 'I'] }) df.ix[df.B.isin(['X','Y','Z']), 'A'] = 'T' print df Output: A B 0 1 G 1 T X 2 3 F 3 T Z 4 5 I Remember to use ix or loc to avoid setting values on a copied

问题 Say I have this array: A, B 1, G 2, X 3, F 4, Z 5, I If column B equals [X, Y or Z] replace column A with value "T" I've found how to change values within the same column but not across, any help would be most appreciated. 回答1: You can try this: import pandas as pd df = pd.DataFrame({ 'A': [1, 2, 3, 4, 5], 'B': ['G', 'X', 'F', 'Z', 'I'] }) df.ix[df.B.isin(['X','Y','Z']), 'A'] = 'T' print df Output: A B 0 1 G 1 T X 2 3 F 3 T Z 4 5 I Remember to use ix or loc to avoid setting values on a copied

问题 I am hoping I am wording this correctly to get across what I am looking for. I need to compare two pieces of text. If the two strings are alike I would like to get scores that are very alike if the strings are very different i need scores that are very different. If i take a md5 hash of an email and change one character the hash changes dramatically I want something to not change too much. I need to compare how alike two pieces of content are without storing the string. Update : I am looking

问题 How should I understand these? null>0 > false null==0 > false null>=0 > true 回答1: The relational operators ( >= and <= ), perform type coercion (ToPrimitive), with a hint type of Number , all the relational operators present have this behavior. You can see the inner details of this process in the The Abstract Relational Comparison Algorithm. On the other hand, the Equals operator ( == ), if an operand is null it only returns true if the other is either null or undefined , no numeric type

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . HSQLDB 2.0 is soon to be released. I wonder if it will outperform H2 since, as far as I know, most users prefer H2 than HSQLDB. I am

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 2 months ago . Does anyone have any information on the performance characteristics of Protocol Buffers versus BSON (binary JSON) or versus JSON in general? Wire size Serialization speed Deserialization speed These seem like good binary protocols for use over HTTP. I'm just wondering which would be better in the long run for a