expression

问题 This is a practice I've seen before, but not very often: A variable is assigned to a value at the same time the value itself is evaluated (or is it the expression itself that is evaluated?). Example: // Outputs "The value is 1" $value = 1; if ($var = $value) { echo "The value is $var"; } Seems to be the same as: $value = 1; $var = $value; if ($var) { echo "The value is $var"; } Another example: // Outputs "The value is 1" $value = 1; echo "The value is ".$var = $value; I've been using this a

问题 I'm experiencing some problems implementing a regular expression for a repeating string pattern. >>> re.findall('(\(\w+,\d+\)(?:,)?)+', '(a,b),(c,d),(e,f)') ['(e,f)'] I would like ro get the other items as well Help would be really appriciated 回答1: Remove the + ; your pattern matches all occurrences, but the group can only capture one occurrence, you cannot repeat a capturing group that way: >>> import re >>> re.findall('(\(\w+,\w+\),?)+', '(a,b),(c,d),(e,f)') ['(e,f)'] >>> re.findall('\(\w+,

问题 Why are they called "primary"? In the order of evaluence they are the first? C++03 standard defines the expression in chapter 5 (Note 1): An expression is a sequence of operators and operands that specifies a computation. Then the 5.1 "Primary expressions" defines the list of primary expressions: (1) primary-expression: literal this ( expression ) id-expression My main question is in connection the third point: ( expression ) So, according to the standard, every expression with brackets are

问题 Is there a way that I can use a normal Rectangle (shape) as part of a clip for another object in XAML. It seems like I should be able to, but the solution is eluding me.. <Canvas> <Rectangle Name="ClipRect" RadiusY="10" RadiusX="10" Stroke="Black" StrokeThickness="0" Width="32.4" Height="164"/> <!-- This is the part that I cant quite figure out.... --> <Rectangle Width="100" Height="100" Clip={Binding ElementName=ClipRect, Path="??"/> </Canvas> I know that I can use a 'RectangleGeometry' type

问题 I want to create a query which has more than 3-4 Expression.Or ? But Expression.Or just let me to add two Expressions inside it. if (!string.IsNullOrEmpty(keyword)) query .Add(Expression.Or( Expression.Like("Name", keyword, MatchMode.Anywhere), Expression.Like("LastName", keyword, MatchMode.Anywhere))) .Add(Expression.Or( Expression.Like("Email1", keyword, MatchMode.Anywhere), Expression.Like("Email2", keyword, MatchMode.Anywhere))); The code above generates "Name like %this% or LastName like

问题 By the expression templates technique, a matrix expression like D = A*B+sin(C)+3.; is pretty much equivalent, in terms of computing performance, to a hand-written for loop. Now, suppose that I have the following two expressions D = A*B+sin(C)+3.; F = D*E; cout << F << "\n"; In a "classical" implementation by expression templates, the computing performance will be pretty much the same as that of two for loops in sequence. This is because the expressions are evaluated immediately after the =

问题 I have the folowing attribute on a div: ng-show="state.name === 'index'" . I've also tried ng-show='state.name === "index" , but I keep getting the following error: Syntax Error: Token ' "index" ' is an unexpected token at column 16 of the expression [state.name === "index"] starting at ["index"] . Why? 回答1: ng-show takes an "AngularJS statement." This type of statement only has an == operator, but this operator behaves like === . It's a bit confusing, but handy in that you cannot shoot

问题 Consider you have table T, with fields A and B. With regular SQL, I could do this: SELECT SUM(A * (100.0 - B) / 100.0) AS D FROM T; And I would get exactly what I expect. However, I'm not sure how to do it with CriteriaQuery. I know how to do sum over 1 field, but not how to do sum over some math expression over multiple fields in a row. 回答1: The CriteriaBuilder interface provides the following arithmetic functions: addition: sum(a, b) substraction: diff(a, b) multiplication: prod(a, b)

问题 I am doing a common query in my project. I use Expression to build my query tree, the code list below: public IList<Book> GetBooksFields(string fieldName, string fieldValue) { ParameterExpression paramLeft = Expression.Parameter(typeof(string), "m." + fieldName); ParameterExpression paramRight = Expression.Parameter(typeof(string), "\"" + fieldValue + "\""); ParameterExpression binaryLeft = Expression.Parameter(typeof(Book),"m"); BinaryExpression binaryExpr = Expression.Equal(paramLeft,

问题 How would I express the following java code in scala? a = b = c; By the way, I'm re-assigning variables (not declaring). 回答1: The closest shortcut syntax in Scala can only be used when you declare a var or val . scala> val c = 1 c: Int = 1 scala> val a, b = c a: Int = 1 b: Int = 1 From the Scala Reference, Section 4.1 A value declaration val x 1 , ... , x n : T is a shorthand for the sequence of value declarations val x 1 : T ; ...; val x n : T. A value definition val p 1 , ..., p n = e is a