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DECLARE ARRAY S; function INIT (words) S ← CREATE_ARRAY (LENGTH (words) + 1) for k ← from 0 to LENGTH (words) do S [k] ← EMPTY_ORDERED_SET function EARLEY_PARSE (words, grammar) INIT (words) ADD_TO_SET ((γ → • S, 0), S [0]) for k ← from 0 to LENGTH (words) do for each state in S [k] do // S[k] can expand during this loop if not FINISHED (state) then if NEXT_ELEMENT_OF (state) is a ...
Perl provides three loop control keywords that all accept an optional loop label as an argument. If no label is specified, the keywords act on the innermost loop. Within nested loops, the use of labels enables control to move from an inner loop to an outer one, or out of the outer loop altogether.
Perl 5 has built-in, language-level support for associative arrays. Modern Perl refers to associative arrays as hashes; the term associative array is found in older documentation but is considered somewhat archaic. Perl 5 hashes are flat: keys are strings and values are scalars.
Perl. Block comments in Perl are considered part of the documentation, and are given the name Plain Old Documentation (POD). 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
In Perl version 5, by default, constructors are factory methods, that is, methods that create and return the object, concretely meaning create and return a blessed reference. A typical object is a reference to a hash, though rarely references to other types are used too.
Impatient Perl – for readers with previous programming experience. Learn Perl in about a week. Learning Perl the Hard Way – for people who know another programming language. Higher-Order Perl – advanced programming in Perl; Perl phrasebook – compare equivalent examples of Perl and Python code, on the Python Wiki; Perl scripts
Folds can be regarded as consistently replacing the structural components of a data structure with functions and values. Lists, for example, are built up in many functional languages from two primitives: any list is either an empty list, commonly called nil ([]), or is constructed by prefixing an element in front of another list, creating what is called a cons node ( Cons(X1,Cons(X2,Cons ...
The empty hash {} is also true; in this context {} is not an empty block, because perl -e 'print ref {}' returns HASH. Evaluated boolean expressions are also scalar values. The documentation does not promise which particular value of true or false is returned. Many boolean operators return 1 for true and the empty-string for false.