^(?:(?:([01]?\d|2[0-3]):)?([0-5]?\d):)?([0-5]?\d)$ Explanation: ^ # Start of string (?: # Try to match… (?: # Try to match… ([01]?\d|2[0-3]): # HH: )? # (optionally). ([0-5]?\d): # MM: (required) )? # (entire group optional, so either HH:MM:, MM: or nothing) ([0-5]?\d) # SS (required) $ # End of string
Func<T, bool> func = expression.Compile(); Predicate<T> pred = t => func(t); Edit: per the comments we have a better answer for the second line: Predicate<T> pred = func.Invoke;
Yes, they are equivalent in behavior. Then why do people use the (1 << 7) version? I guess, they use it to document it is a power of 2. Calculating the condition every time must be an overhead! I am unable to find the reason behind this! Not really, any normal compiler will replace 1 … Read more
PropertyExpression is internal You should cast it to System.Linq.Expressions.MemberExpression instead, as suggested in this post.
This depends on the language, but in C style languages % is the same precedence as * and /. This means that if it appears in the same expression (without parentheses) the order depends on the associativity. In this case % is usually left-associative, so the operators will be executed in left-to-right order.
Applying the logical not (!) operator twice has the purpose of normalising a value to be either 0 or 1. In a control expression of an if-statement, that doesn’t make any difference. The if-statement only cares about the value being zero or nonzero, the little !! dance is completely useless. Some coding style guides might mandate … Read more
The correct answer (note the brackets): (//span[@class=”Big”])[1] The following expression is wrong in the general case: //span[@class=”Big”][1] because it selects every span element in the document, that satisfies the condition in the first predicate, and that is the first such child of its parent — there can be many such elements in an XML document … Read more
text() and node() are node tests, in XPath terminology (compare). Node tests operate on a set (on an axis, to be exact) of nodes and return the ones that are of a certain type. When no axis is mentioned, the child axis is assumed by default. There are all kinds of node tests: node() matches … Read more
Use the case construct: select ‘Test Name’, case when foo = ‘Result’ then 1 else 0 end from bar where baz = (some criteria) Also see the MSDN Transact-SQL CASE documentation.
Using a more functional approach, you can implement the match with a one-liner using an array function: ECMAScript 6: const regexList = [/apple/, /pear/]; const text = “banana pear”; const isMatch = regexList.some(rx => rx.test(text)); ECMAScript 5: var regexList = [/apple/, /pear/]; var text = “banana pear”; var isMatch = regexList.some(function(rx) { return rx.test(text); });