Difference between revisions of "Context-free grammar"
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A production may include vertical bars or curly braces by using the following predefined nonterminals: | A production may include vertical bars or curly braces by using the following predefined nonterminals: | ||
* <code>{!}</code> - expands to a | | * <code>{!}</code> - expands to a | | ||
| − | * <code> | + | * <code>{(}</code> - expands to a { |
| − | * <code>{)}</ | + | * <code>{)}</code> - expands to a } |
Revision as of 15:25, 29 July 2016
Context-free grammar can be used to generate random strings, from short words to entire paragraphs. If you are interested in its theory, read more on [1].
Syntax
In WML, it uses its own simple syntax. It is usually a translatable string and should be in <<French quotation marks>>. The code is composed from nonterminals. They are written on separate lines. Each nonterminal is substituted by one of its possibilities separated by the | symbol, the name is separated from possibilities with =. The nonterminal that makes the result is named main. The possibilities can contain other nonterminals, marked by {curly brackets}.
Examples
name_generator= _ <<
main=Hello world|Hi world|Ahoi world
>>
The result is either Hello world or Hi world or Ahoi world.
name_generator= _ <<
main=Hello {noun}|Hi {noun}
noun=world|planet|Universe|Earth
>>
The result is either Hello or Hi, followed by one of the four possible nouns, world, planet, Universe or Earth.
Other rules
A nonterminal can reference itself, which can, under the right circumstances, lead to a loop that expands indefinitely, causing a stack overflow. Avoid this unless you really know what you are doing.
Each nonterminal has a reduced probability for possibilities that were chosen the last time.
A production may include vertical bars or curly braces by using the following predefined nonterminals:
{!}- expands to a |{(}- expands to a {{)}- expands to a }