nested

问题 Can a macro be written in Scheme (with define-syntax , for example) which will take expressions like this: (op a b c d e f g h i j) And yield expressions like this as output? (op (op (op (op (op (op (op (op (op a b) c) d) e) f) g) h) i) j) Of course, for arbitrary lengths. I can't think of a way to do it, given some template like this: (define-syntax op (syntax-rules () [(_) 'base-case] [(v1 v2 ...) 'nested-case??])) 回答1: (define bop list) (define-syntax op (syntax-rules () ((op a b) (bop a b

问题 This question already has answers here : Can inner classes access private variables? (5 answers) Closed 3 years ago . The title already says a lot, but basically what i want to do is the following(Example): I have a class called A, and another class inside a called B, like so: class A { int a; class B { void test() { a = 20; } }; }; As you can see my goal is for class B to have access to class A, as it is a nested class. Not this wont work, because B doesn't have access to A, but how can it

问题 I expect (hope even) that this will be a stupid question, but after wrestling for many hours with this problem I need some insight. My iOS 5.1 app uses nested MOCs, having a PrivateQueueConcurrency child MOC, call it MOC-Child, whose parent is a MainQueueConcurrency MOC, call it MOC-Parent. MOC-Parent backs a table view that displays its entities. MOC-Child is used by a parser, which runs asynchronously on a non-main thread, to create new entities that correspond to XML entity-descriptions

问题 The mobile app of Twitter has a scrollable tab in the middle of the screen when you are on your profile. The top half of the screen displaying your profile info etc doesn't change when you click on the scrollable tabs mid screen : "Tweets & replies", "Media" etc. I am wondering how one would create this? Having half the screen stay the same and then having tabs which change mid screen... At the moment I have react navigation tabs as my main navigation - so on one of these tabs (the profile

问题 I am now trying for some hours to remove a nested hash key of a hash list. I saw many solution non-nested hashs wich looks like this: sample_hash = {"key1" => "value1", "key2" => "value2"} sample_hash.except("key1") This results in: {"key2"=>"value2"} But if I try to use the except method on a hash with nested key then it doesn't work. Here my code: nested_hash = {"key1"=>"value1", "key2"=>{ "nested_key1"=>"nestedvalue1", "nested_key2"=>"nestedvalue2" } } nested_hash.except("nested_key2") The

问题 Why is a nested cast NOT working in MySQL? (It does using SQL Server) select cast(cast(myColumn as decimal(5,2)) as int) from myTable SQLFiddle Example 回答1: According to the manual: CAST(expr AS type) [...] CONVERT(expr,type) [...] The type can be one of the following values: BINARY[(N)] CHAR[(N)] DATE DATETIME DECIMAL[(M[,D])] SIGNED [INTEGER] TIME UNSIGNED [INTEGER] So, just follow the manual: SELECT CAST(CAST(myColumn AS DECIMAL(5,2)) AS SIGNED) FROM myTable or SELECT CAST(CAST(myColumn AS

问题 Does anyone know what Join algorith does LINQ performs with its Join operator. Is it NestedLoop, Merge, or HashSet? Is there any way to specify a different one, if supported? Regards Albert 回答1: First it effectively creates a lookup from the "inner" sequence, then iterates through the outer sequence. It can then look up each key from the outer sequence and yield each appropriate pair. Something like this (ignoring argument validation etc): public static IEnumerable<TResult> Join<TOuter,

问题 int num = n/4; for (int i = 1; i <= num; i++) { for (int j = 1; j <= n; j++) { for (int k = 1; k <= n; k++) { int count = 1; } } } According to the books I have read, this code should be O((n^3)/4). But apparently its not. to find the Big-O for nested loops are you supposed to multiply the bounds? So this one should be num *n *n or n/4 *n *n. 回答1: O((n^3)/4) makes no sense in terms of big-O notation since it's meant to measure the complexity as a ratio of the argument. Dividing by 4 has no

问题 I cant seem to get this nested for loop to work correctly, I want to print all of the tracks on the EP in the row with the EP name and other details. Everything from the first for-each loop displays correctly but nothing is pulled through for the for-each loop to get the tracks. Here is my XML <dalehoward> <ep> <name>Letters EP</name> <year>2012</year> <label>Static Audio</label> <image>letters.jpg</image> <tracks> <track number="1"> <tname>Letters</tname> <length>6.35</length> </track>

问题 I've got a dict that looks something like this: d = {'Food': {'Fruit' : {'Apples' : {'Golden Del.' : ['Yellow'], 'Granny Smith' : ['Green'], 'Fuji' : ['Red'], }, 'Cherries' : ['Red'], 'Bananas' : ['Yellow'], 'Grapes' : {'Red Grapes' : ['Red'], 'Green Grapes' : ['Green'], }, }, 'Dessert': {'Baked Ds' : {'Cakes' : {'Yellow Cake' : ['Yellow'], 'Red Velvet' : ['Red'], }, 'Cookies' : ['Yellow'], }, }, 'Steak' : ['Red'], }, 'Other': ['Blue'], } So basically, an n-nested dict, where each value is