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Technically, Perl does not have a convention for including block comments in source code, but POD is routinely used as a workaround. PHP. PHP supports standard C/C++ style comments, but supports Perl style as well. Python. The use of the triple-quotes to comment-out lines of source, does not actually form a comment. [19]
Note that fmap, join, append and bind are well-defined, since they're applied to progressively deeper arguments at each recursive call. The list type is an additive monad, with nil as the monadic zero and append as monadic sum. Lists form a monoid under the append operation. The identity element of the monoid is the empty list, nil.
Python sets are very much like mathematical sets, and support operations like set intersection and union. Python also features a frozenset class for immutable sets, see Collection types. Dictionaries (class dict) are mutable mappings tying keys and corresponding values. Python has special syntax to create dictionaries ({key: value})
The append procedure takes zero or more (linked) lists as arguments, and returns the concatenation of these lists. ( append ' ( 1 2 3 ) ' ( a b ) ' () ' ( 6 )) ;Output: (1 2 3 a b 6) Since the append procedure must completely copy all of its arguments except the last, both its time and space complexity are O( n ) for a list of n {\displaystyle ...
A line break that is visible in the content is inserted by pressing ↵ Enter twice. Pressing ↵ Enter once will place a line break in the markup, but it will not show in the rendered content, except when using list markup. Markup such as bold or italics will be terminated at a line break.
Scripts such as pyp or Pyline import commonly used modules and provide more human-readable variables in an attempt to make Python functionality more accessible on the command line. Here is a redo of the above example (printing the last field of a unix long listing):
Python 2 also distinguishes two types of strings: 8-bit ASCII ("bytes") strings (the default), explicitly indicated with a b or B prefix, and Unicode strings, indicated with a u or U prefix. [25] while in Python 3 strings are Unicode by default and bytes are a separate bytes type that when initialized with quotes must be prefixed with a b.
This allows PHP to perform string interpolation in double quoted strings, where backslash is supported as an escape character. No escaping or interpolation is done on strings delimited by single quotes. PHP also supports a C-like sprintf function. Code can be modularized into functions defined with keyword function.