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In Lua, "table" is a fundamental type that can be used either as an array (numerical index, fast) or as an associative array. The keys and values can be of any type, except nil. The following focuses on non-numerical indexes. A table literal is written as { value, key = value, [index] = value, ["non id string"] = value }. For example:
A table is a sequence, optionally supplemented by named keys: digit["two"]="2". Several table functions like table.concat will only work with the numbered values and ignore named keys. The metatable offers a large, optional set of methods for altering table behavior. For example, you can define a table to be callable like a function.
Lua provides functions to push and pop most simple C data types (integers, floats, etc.) to and from the stack, and functions to manipulate tables through the stack. The Lua stack is somewhat different from a traditional stack; the stack can be indexed directly, for example. Negative indices indicate offsets from the top of the stack.
Decision tables can be used as an aid to clarifying the logic before writing a program in any language, but in the 1960s a number of languages were developed where the main logic is expressed directly in the form of a decision table, including: Filetab
Lookup, find, or get find the value (if any) that is bound to a given key. The argument to this operation is the key, and the value is returned from the operation. If no value is found, some lookup functions raise an exception, while others return a default value (such as zero, null, or a specific value passed to the constructor).
Substring.size (#1 (Substring.position substring (Substring.full string))) Standard ML: returns string length [string rangeOfString:substring].location: Objective-C (NSString * only) returns NSNotFound string.find(string, substring) (string):find(substring) Lua: returns nil string indexOfSubCollection: substring startingAt: startpos ifAbsent ...
Lua does not contain a separate ephemeron construct, but its table data structures may be set to holds its keys, values, or both in a weak fashion. If the keys are held weakly, but values are held strongly, the table will act like an ephemeron. Lua 5.4 also introduces metatable behavior that helps to construct ephemeron-like data structures. [4]
function factorial (n is a non-negative integer) if n is 0 then return 1 [by the convention that 0! = 1] else if n is in lookup-table then return lookup-table-value-for-n else let x = factorial(n – 1) times n [recursively invoke factorial with the parameter 1 less than n] store x in lookup-table in the n th slot [remember the result of n! for ...