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However, a generator is an object with persistent state, which can repeatedly enter and leave the same scope. A generator call can then be used in place of a list, or other structure whose elements will be iterated over. Whenever the for loop in the example requires the next item, the generator is called, and yields the next item.
[5] [6] [7] A line comment ends at the end of the text line. In modern languages, a line comment starts with a delimiter but some older languages designate a column at which subsequent text is considered comment. [7] Many languages support both block and line comments – using different delimiters for each.
AutoHotkey: As the first character of continued line; any expression operators except ++ and --, and a comma or a period [7] Some form of line comment serves as line continuation. Turbo Assembler: \ m4: dnl; TeX: % Character position. Fortran 77: A non-comment line is a continuation of the prior non-comment line if any non-space character ...
Generally, var, var, or var is how variable names or other non-literal values to be interpreted by the reader are represented. The rest is literal code. Guillemets (« and ») enclose optional sections.
Parse tree of Python code with inset tokenization. The syntax of textual programming languages is usually defined using a combination of regular expressions (for lexical structure) and Backus–Naur form (a metalanguage for grammatical structure) to inductively specify syntactic categories (nonterminal) and terminal symbols. [7]
Comments are allowed as: /* This is a comment */ and // This is a line comment. As in C, whitespace are generally insignificant to syntax. Value statements terminate by a semicolon. One limitation of the original NeXT property list format is that it could not represent an NSValue (number, Boolean, etc.) object.
In Python, a generator can be thought of as an iterator that contains a frozen stack frame. Whenever next() is called on the iterator, Python resumes the frozen frame, which executes normally until the next yield statement is reached. The generator's frame is then frozen again, and the yielded value is returned to the caller.
A classic example of a problem which a regular grammar cannot handle is the question of whether a given string contains correctly nested parentheses. (This is typically handled by a Chomsky Type 2 grammar, also termed a context-free grammar .)