expression

问题 I am currently taking an AP Computer Science class in my school and I ran into a little trouble with one of my projects! The project requires me to create a calculator that can evaluate an expression and then solve it. I have got most of that down, but I ran into a little trouble because my teacher asked me to use a while loop to continuously ask for input and display the answer, and I am stuck on that. To end the program the user has to type in "quit" and I can't use system.exit() or any

问题 How to combine these expression Expression<Func<int, int>> f1 = i => i + 1; Expression<Func<int, int>> f2 = i => i + 2; Expression<Func<int, int, int>> f3 = (i, j) => i * j; to Expression<Func<int, int>> f4 = i =>(i+1)*(i+2); while running? Here's the code. I want to write a extend method but it don't work in linq2entities public static IQueryable<TRe> LeftJoin<TLeft, TRight, TKey, TRe>(this IQueryable<TLeft> left, IQueryable<TRight> right, Expression<Func<TLeft, TKey>> leftKeySel, Expression

问题 I have searched and searched.. I have a bash script that is used to run a psql query and email the results on a daily basis. The DB does not update till midnight and my bash script passes a variable to the query for the day prior. I am getting this error only when I use the passed variable otherwise if I put the date in the query manually it runs fine. Not quite sure for I am still learning psql and bash. Here is the bash script: #!/bin/bash NOWDATE=`date +%Y-%m-%d -d "yesterday"` SUBDATE=

问题 This question already has answers here : A comprehensive regex for phone number validation (41 answers) Closed 3 years ago . XXX-XXX-XXXX XXXXXXXXXX I want to use a regular expression of the format. I tried as shown below, and an error occurs. How do I fix it? sample var regExp = / ^ 01 ([0 | 1 | 6 | 7 | 8 | 9]?) - ([0-9] {3}) - ([0-9] {4}) $ /??; sample var regExp = / ^ 01 ([0 | 1 | 6 | 7 | 8 | 9]?) ([0-9] {3}) ([0-9] {4}) $ /??; 回答1: sample 1 var regExp = /^01([016789]?)-([0-9]{3})-([0-9]{4

问题 I want to call a method like this: signature: void Method(object a, object b, params LambdaExpression[] expressions); call: Method(a, b, x => x.A, x => x.B) Is it possible? Let's assume that the type of 'x' is a constant type. For example, if x => x.A and y => y.B were Funcs, they'd be Func<TType,*> , such that the params array always had the same type for TType , but the return value's type * could differ from element to element of the params array. That's why I had to choose something more

问题 I currently have this validation expression that I am using to validate a complete string: (Thanks to many people including @CinCout) ^((?P *\begin{(?matrix|matrix*|pmatrix|pmatrix*|bmatrix|bmatrix*|Bmatrix|Bmatrix*|vmatrix|vmatrix*|Vmatrix|Vmatrix*|\left|\right)}(?:{c+})?\s(?:(?: *one|two|three){0,3} (-?\d *)?(?:& ?|(\\ *\n)))+ *\end{\g} \s?)|\s \$\s*(?P>matrix) *\$| *\$\$\s(?P>matrix) \$\$|\s \[\s*(?P>matrix) \]|\s \(\s*(?P>matrix) *\))$ I currently force the user to enter "\" after each

问题 I have a problem using the Logical OR operator in C++. The problem is coming that the right-side expression is not evaluated if the left-side is true. I have two deque-s and I need to popLeft from them with a while, but if I can pop from the first deque, I don't pop from the second because is not evaluated, by the OR operator. How can I overcome this problem. Here is the piece of code: while( D.popLeft( k ) || E.popLeft( m ) ) { if( k < m ) { C.pushRight( k ); E.pushLeft( m ); } else { C

问题 I have two text boxes in my SSRS report. The Total Number is simply - =COUNT(Fields!CommunicationId.Value) The First Call Resolutions = =SUM(Fields!FirstCallResolution.Value) The FirstCallResolution simply has a 1 for when it is a first call resolution and a 0 when it is not. What would the expression be to get this to show the % correctly in SSRS? Thanks Edit : format code 回答1: You can do calculations in your expressions. Try =(SUM(Fields!FirstCallResolution.Value) / COUNT(Fields

问题 Given the following linq-query: var query1 = dbContext.MainTable.Where(m => m.MainId == _mainId).SelectMany(sub => sub.SubTable1) .Select(sub1 => new { sub1.CategoryName, VisibleDivisions = sub1.SubTable2 .Where(sub2 => sub2.Status == "Visible") .Select(sub2 => new { /* select only what needed */ }) }); Starting from my main-table, I want to get all sub1's selected together with all the sub2's related to the sub1. The query works as expected, generating a single query which will hit the

问题 I'm having a go at making a flexible exporter to export info from a SQL db accessed via LINQ to SQL, whereby the program can dynamically choose which fields to select and do all the processing server side. The final aim is to have a simple statement like: var result = db.Product.Select(p => selector(p)); Where selector is a dynamically created Expression Tree describing the fields to select. Currently, I have each of the db fields assigned to it's own individual selector like: Expression<Func