expression

问题 I have needed in several occasions some classes to represent and manipulate conditions (typically in a UI so the user builds a query by combining different condition types and then the code can transform that depending on the underlying system to be queried, for example lucene and a db). I searched all over for a reusable set of classes, I am sure this has to be used in many existing places (all the expression languages for starters) but could not find anything easily usable. I ended up

问题 I just stomped at a begin...end in Erlang's documentation (here), but it doesn't give some examples of how it is useful. Looking here in StackOverflow I found two cases where people would be using begin...end , both in list comprehensions: https://stackoverflow.com/a/5645116/979505 https://stackoverflow.com/a/5141263/979505 But I wonder if there are more of such uses. Can anyone provide another scenario in which a begin...end is useful in Erlang? Thanks 回答1: Macros, for example: -define(M(A,

问题 Can I use an Expression to set a variable in a "SQL Statement Task" ? I am designed an ETL solution loading a plain text file from a website. The user write the main parameters, like month, year, registercount, and press the processing button. The ETL solution starts. Until now, I am used to read/set variables with SQL statements inside same "SQL Statement Task" but sometimes they do not work properly when the solution is started from the web app with these same params used to set these

问题 I have a string: Some string, "it's a nice string". I like it. "some other text" I want remove spaces, excluding there beetween ": Somestring,"it's a nice string".Ilikeit."some other text" How I can goal this? 回答1: You could use regular expressions, or you could cheat and use explode() : $text_before = 'Some string, "it\'s a nice string". I like it. "some other text"'; $text_after = array(); $text_quotes = explode('"', $text_before); for ($i = 0, $max = count($text_quotes); $i < $max; $i++) {

问题 Is there a way in Python to parse a mathematical expression in Python that describes a 3D graph? Using other math modules or not. I couldn't seem to find a way for it to handle two inputs. An example of a function I would want to parse is Holder Table Function. It has multiple inputs, trigonometric functions, and I would need to parse the abs() parts too. I have two 2D numpy meshgrids as input for x1 and x2, and would prefer to pass them directly to the expression for it to evaluate. Any help

问题 I need to create a Calculation in the SQL Server Data Tools. Imagine that in my OLAP structure I have a City and a Seller Dimensions, and a fact. And in the City Dimension I have a city, a state, and a Population, and this is a Measure in a Dimension. I need to sum the Population in the cities which have sales. But I can't sum only the cities with sales, I can only show the state's total population. One seller can sell in many cities. Example: I'll filter by seller John and the query returns

问题 I'm currently working on an EF website where I have this database object: public partial class Association { public Association() { this.Users = new HashSet<User>(); } public Guid Id { get; set; } public Guid ItemId { get; set; } [ForeignKey("ItemId")] public virtual Item Item { get; set; } [InverseProperty("Association")] public virtual ICollection<User> Users { get; set; } } An Item class: public partial class Item { public Item() { this.Associations = new HashSet<Association>(); } public

问题 I'm using basic .net DataColumns and the associated Expression property. I have an application which lets users define which columns to select from a database table. They can also add other columns which perform expressions on the data columns resulting in a custom grid of information. The problem I have is when they have a calculation column along the lines of "(C2/C3)*100" where C2 and C3 are data columns and the value for C3 is zero. The old "divide by zero" issue. The simple answer would

问题 I’ve written part of a mathematical calculator program. I’ve finished the parser of the program, so when a user types in a mathematical expression as a string, I already have a way to obtain a corresponding data structure of the following type: type expression = | Term of int | Addition of expression * expression | Multiplication of expression * expression | Subtraction of expression * expression All I need now is a way to evaluate these kinds of data structures. (a) Write the expression

问题 I've been trying to get this regex down and searched alot for answers What I need is to get the nth (4th in this example) line from a text file I got this down atm ^(?<=([^\n]*\n){3})[^\n]*\n But it doesn't seem to work (something about needing fixed length patterns in lookbehind) Is there any way to overcome that obstacle? Can anyone provide a correction\different regex if needed for this problem? Thanks Edit: I'm trying this regex in PowerGrep and it just doesn't work P.S: Is there a way of