Lambda expressions can be converted to delegates or expression trees (with some restrictions); anonymous methods can only be converted to delegates Lambda expressions allow type inference on parameters: Lambda expressions allow the body to be truncated to just an expression (to return a value) or single statement (in other cases) without braces. Lambda expressions allow … Read more
Regarding calling one method : Direct call can’t be beaten speed-wise. Using Expression API is globally similar to using Reflection.Emit or Delegate.CreateDelegate speed-wise (Small differences could be measured; as always optimizing for speed without measurements and goals is useless). They all generate IL and the framework will compile it to native code at some point. … Read more
Expression.Quote specifies that a lambda is to be treated as an expression tree and not as a function. It induces closure semantics on its operand. When you are constructing a MethodCallExpression using Expression.Call, any parameters that are lambda expressions (LambdaExpression/Expression<TDelegate>) must use Expression.Quote to wrap the parameter before passing in. So for a parameter of … Read more
On Rails 4+ with a Postgres database the general form of a RegEx query is: Model.where(“column ~* ?”, ‘regex’) As for the regex, it can be a general ‘^A\d+$’ or more specific ‘^A\d{4}$’ Breaking it down: ^ – string start anchor A – literal “A” \d+ – one or more digits (0-9) \d{4} – exactly … Read more
There is no difference in performance. However, the first style is ANSI-89 and will get your legs broken in some shops. Including mine. The second style is ANSI-92 and is much clearer. Examples: Which is the JOIN, which is the filter? FROM T1,T2,T3…. WHERE T1.ID = T2.ID AND T1.foo = ‘bar’ AND T2.fish = 42 … Read more
The assignment operator in Java evaluates to the assigned value (like it does in, e.g., c). So here, readLine() will be executed, and its return value stored in line. That stored value is then checked against null, and if it’s null then the loop will terminate.
There is no default clause in the SSRS Switch expression. However, you can always modify your expression slightly: =Switch ( Parameters!UserFranNr.Value = “99”,”ID99″, Parameters!UserFranNr.Value = “87”,”ID87″, true, “ID0” ) Since any time the last condition is hit it will be explicitly evaluated to true, the last row will effectively act as a default value. I’ve … Read more
You can have a look at the type ExpressionEqualityComparer that is used inside Linq to db4o. It implements the interface IEqualityComparer<T>, so it’s usable for generic collections, as well as for a standalone usage. It uses the type ExpressionComparison to compare two Expressions for equality, and HashCodeCalculation, to compute a hashcode from an Expression. It … Read more
The method created via DynamicMethod goes through two thunks, while the method created via Expression<> doesn’t go through any. Here’s how it works. Here’s the calling sequence for invoking fn(0, 1) in the Time method (I hard-coded the arguments to 0 and 1 for ease of debugging): 00cc032c 6a01 push 1 // 1 argument 00cc032e … Read more
What am I missing? Why not: url.split(‘?’)[0]