Yes. 6.5.2.1 paragraph 1 (C99 standard) describes the arguments to the [] operator: One of the expressions shall have type “pointer to object type“, the other expression shall have integer type, and the result has type “type“. 6.5.2.1 paragraph 2 (emphasis added): A postfix expression followed by an expression in square brackets [] is a … Read more
The square brackets produce a list/array. The curly brackets produce an object with key/value pairs. The list can then be a value of a key/value pair.
RFC 3986 states A host identified by an Internet Protocol literal address, version 6 [RFC3513] or later, is distinguished by enclosing the IP literal within square brackets (“[” and “]”). This is the only place where square bracket characters are allowed in the URI syntax. So you should not be seeing such URI’s in the … Read more
Curly braces create dictionaries or sets. Square brackets create lists. They are called literals; a set literal: aset = {‘foo’, ‘bar’} or a dictionary literal: adict = {‘foo’: 42, ‘bar’: 81} empty_dict = {} or a list literal: alist = [‘foo’, ‘bar’, ‘bar’] empty_list = [] To create an empty set, you can only use … Read more
Try this: class risc { // singleton protected: static unsigned long registers[8]; public: unsigned long operator [](int i) const {return registers[i];} unsigned long & operator [](int i) {return registers[i];} };
The zero value for map types is nil. It is not yet initialized. You cannot store values in a nil map, that’s a runtime panic. In your last example you initialize the (outer) data map, but it has no entries. When you index it like data[“a”], since there is no entry with “a” key in … Read more
There is a plain-text database of information about every Unicode character available from the Unicode Consortium; the format is described in Unicode Annex #44. The primary information is contained in UnicodeData.txt. Open and close punctuation characters are denoted with Ps (punctuation start) and Pe (punctuation end) in the General_Category field (the third field, delimited by … Read more
The square brackets are a synonym for the test command. An if statement checks the exit status of a command in order to decide which branch to take. grep -q “$text” is a command, but “$name” = ‘Bob’ is not–it’s just an expression. test is a command, which takes an expression and evaluates it: if … Read more
In a character class (square brackets) any character except ^, -, ] or \ is a literal. This website is a brilliant reference and has lots of info on the nuances of different regex flavours. http://www.regular-expressions.info/refcharclass.html
Following [] is supported in PHP >= 5.4: [‘name’ => ‘test’, ‘id’ => ‘theID’] This is a short syntax only and in PHP < 5.4 it won’t work.