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############################################################################
#
# File: lsystem.icn
#
# Subject: Procedures for Lindenmayer systems support
#
# Author: Stephen B. Wampler
#
# Date: May 2, 2001
#
############################################################################
#
# This file is in the public domain.
#
############################################################################
#
# Version: 1.0
#
############################################################################
#
# Comments: This package is the collection of routines
# developed to facilitate experiments with L-systems,
# including the interpretation of strings as turtle
# graphics commands.
#
# Only rudimentary L-systems are currently implemented.
# users are encouraged to extend this system.
#
############################################################################
#
# Requires: Version 9 graphics, co-expressions (for glib.icn)
#
############################################################################
#
# Links: glib
#
############################################################################
link glib
record Lsys(order, dist, delta, axiom, rewrite)
# lsmap(s1,T) - replace, in s1, occurrences of character key values in T
# with assigned value for that key. (Suitable for l-system rules!)
#
procedure lsmap(s1,T)
local s
if type(T) ~== "table" then
stop("lsmap() - second argument not a table!")
s := ""
s1 ? while s ||:= (\T[move(1)] | move(1))
return s
end
# mk_map(L) - build a rewriting map table from list L
#
procedure mk_map(L)
local a, t
t := table()
every a := !L do {
t[a[1]] := a[2]
}
return t
end
# read_Lsystem(f) - read in an L system from a file...
#
# Form for an L_system:
#
# order: n
# delta: angle
# axiom: string
# map: c = string
#
procedure read_Lsystem(f)
local ls, line, next_token
ls := Lsys(0,10,90,"",table())
while line := read(f) do {
next_token := create gen_tokens(line)
case map(@next_token) of {
"order:": ls.order := integer(@next_token)
"dist:" : ls.dist := integer(@next_token)
"delta:": ls.delta := numeric(@next_token)
"axiom:": ls.axiom := @next_token
"map:" : ls.rewrite[@next_token] := (@next_token, @next_token)
}
}
return ls
end
# write_Lsystem(ls) - display L-system ls (for debugging, mainly)
#
procedure write_Lsystem(ls)
write("L-system:")
write("\torder: ",ls.order)
write("\t dist: ",ls.dist)
write("\tdelta: ",ls.delta)
write("\taxiom: ",ls.axiom)
every key := key(ls.rewrite) do
write("\t map: ",key," -> ",ls.rewrite[key])
return
end
# build_cmd(ls) - return the command string for
# l-system ls
#
procedure build_cmd(ls)
local s
s := ls.axiom
every 1 to ls.order do
s := lsmap(s, ls.rewrite)
return s
end
# eval_cmd(s) - apply turtle t to command string
#
procedure eval_cmd(t,s,dist,delta)
s ? while obey(t,move(1), dist, delta)
return
end
# eval_lsys(t,ls,dist,delta) - apply turtle t directly to
# an Lsystem avoids constructing full Lsystem string
# at once (i.e. no need to call build_cmd).
#
procedure eval_lsys(t,ls)
evaluate(t,ls.axiom, ls.rewrite, ls.order, ls.delta, ls.dist)
end
# evaluate(t,s, Ls_map, n, delta, dist) - recursive l-system evaluation
# (avoids building entire command string)
procedure evaluate(t, s, Ls_map, n, delta, dist)
if n = 0 then return eval_cmd(t,s,dist,delta)
s ? while evaluate(t, lsmap(move(1), Ls_map), Ls_map, n-1, delta, dist)
return
end
# obey(t, c, dist, delta) - execute the appropriate turtle command
# using turtle t. (INCOMPLETE) (this is where L-systems could
# be greatly extended.)
procedure obey(t, c, dist, delta)
case c of {
"f" : Move_Forward(t, dist)
"+" : Left(t, delta)
"-" : Right(t, delta)
default: Line_Forward(t, dist)
}
return
end
# get_tokens(s) - suspend the tokens in string s
#
procedure gen_tokens(s, ws)
local nws
/ws := ' \t'
nws := ~ws
s ? while tab(upto(nws)) do
suspend tab(many(nws)) \ 1
end
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