Tutorial by Topics: expressions

A lambda expression is a syntax for creating anonymous functions inline. More formally, from the C# Programming Guide: A lambda expression is an anonymous function that you can use to create delegates or expression tree types. By using lambda expressions, you can write local functions that can ...

Lambda expressions provide a clear and concise way of implementing a single-method interface using an expression. They allow you to reduce the amount of code you have to create and maintain. While similar to anonymous classes, they have no type information by themselves. Type inference needs to happ...

A regular expression is a special sequence of characters that helps in matching or finding other strings or sets of strings, using a specialized syntax held in a pattern. Java has support for regular expression usage through the java.util.regex package. This topic is to introduce and help developers...

let regex = /pattern/[flags] let regex = new RegExp('pattern', [flags]) let ismatch = regex.test('text') let results = regex.exec('text') FlagsDetailsgglobal. All matches (don't return on the first match).mmulti-line. Causes ^ & $ to match the begin/end of each line (not only begin/e...

For many programmers the regex is some sort of magical sword that they throw to solve any kind of text parsing situation. But this tool is nothing magical, and even though it's great at what it does, it's not a full featured programming language (i.e. it is not Turing-complete). What does 'regu...

Python makes regular expressions available through the re module. Regular expressions are combinations of characters that are interpreted as rules for matching substrings. For instance, the expression 'amount\D+\d+' will match any string composed by the word amount plus an integral number, separate...

for {clauses} body for {clauses} yield body for (clauses) body for (clauses) yield body ParameterDetailsforRequired keyword to use a for loop/comprehensionclausesThe iteration and filters over which the for works.yieldUse this if you want to create or 'yield' a collection. Using yield wil...

[[ -OP $filename ]] [[ $file1 -OP $file2 ]] [[ -z $string ]] [[ -n $string ]] [[ "$string1" == "$string2" ]] [[ "$string1" == $pattern ]] The [[ … ]] syntax surrounds bash built-in conditional expressions. Note that spaces are required on either side of th...

WITH QueryName [(ColumnName, ...)] AS (   SELECT ... ) SELECT ... FROM QueryName ...; WITH RECURSIVE QueryName [(ColumnName, ...)] AS (   SELECT ...   UNION [ALL]   SELECT ... FROM QueryName ... ) SELECT ... FROM QueryName ...; Official documentation: WITH clause A Common ...

preg_replace($pattern, $replacement, $subject, $limit = -1, $count = 0); preg_replace_callback($pattern, $callback, $subject, $limit = -1, $count = 0); preg_match($pattern, $subject, &$matches, $flags = 0, $offset = 0); preg_match_all($pattern, $subject, &$matches, $flags = PREG_PATTERN...

WITH cte_name [(column_name_1, column_name_2, ...)] AS (cte_expression) It is necessary to separate a CTE from the previous statement with a semi-colon (;) character. i.e. ;WITH CommonTableName (...) SELECT ... FROM CommonTableName ... A CTE's scope is a single batch, and only downstream ...

Regular Expressions (sometimes called regexs or regexps) are a textual syntax which represents the patterns which can be matched in the strings operated upon. Regular Expressions, introduced in c++11, may optionally support a return array of matched strings or another textual syntax defining how to...

Fold Expressions are supported for the following operators             +-*/%\ˆ&|<<>>+=-=*=/=%=\ˆ=&=|=<<=>>====!=<><=>=&&||,.*->* When folding over an empty sequence, a fold expression is ill-formed, except for the following three operators: ...

An F() expression is a way for Django to use a Python object to refer to the value of model field or annotated column in the database without having to pull the value into Python memory. This allows developers to avoid certain race conditions and also filtering results based on model field values. ...

re.findAllIn(s: CharSequence): MatchIterator re.findAllMatchIn(s: CharSequence): Iterator[Match] re.findFirstIn(s: CharSequence): Option[String] re.findFirstMatchIn(s: CharSequence): Option[Match] re.findPrefixMatchIn(s: CharSequence): Option[Match] re.findPrefixOf(s: CharSequence): Option[St...

Another benefit from using braced expression strings is that the byte compiler usually can generate more efficient code (5 - 10x faster) from them.