rewriteString
a stream variant of a lindenmayer system (see also L-Systems in SC)experimental, might change interface.
see also_
An initial stream, the axiom, is recursively rewritten, using a set
of production rules. In a classic lindenmayer system (L-system),
each level of rewriting is done at once, rewriting the whole string.
This can be also done in a depth-first traversal through all levels,
taking in a stream and resulting in a stream.
The L-system's restrictions to a general generative grammar is its
fixed order in which the rules are applied,
and no principal distinction between terminal and nonterminal symbols.
If one of the two special characters < and > appear in a set of rules,
they are interpreted as context in order to form a context-sensitive generative grammar.
Everything that falls outside the closure such as A and B in A<X>B are not
rewritten if AXB match: X is rewritten only.
The class Prewrite by James McCartney does a similar thing with objects, whereby
their identity is used as a lookup. This is more efficient, but does not allow for the
combinatorics that a pure string rewriting system does.
Note that for some context-sensitive grammars there is an ambiguitiy which needs to be fixed (left-side dependency).
download: LazyLindenmayer
// the new version allows context-sensitive grammars: // "X<A>Y", where X,A,Y is any number of characters. ( r = "xuabcyyyyxcccxx"; r.rewriteString([ "a<b>c" -> "Z", "xx" -> "yy", "y<xcc" -> "P", "x>u" -> "......", "." -> "/" ], 2) ) // results in: //////uuaZcbcyyyyPxcccyy
further information:
http://www.math.okstate.edu/mathdept/dynamics/lecnotes/node15.html
http://en.wikipedia.org/wiki/Lindenmayer_system
http://en.wikipedia.org/wiki/Chomsky_grammar
an introduction to L-systems for composers and animators
L-Systems in SC
