Rit version 1.3

	Rit is a PHP like language that is designed for use in Plan 9.
	The name came from "rc in text"

	You can examine Rit by processing this text:
		rit readme
	and compare the output with this file.
	You will find Rit manual in my web page:
	http://plan9.aichi-u.ac.jp/pegasus/eman-2.1/
	or if you want Japanese manual:
	http://plan9.aichi-u.ac.jp/pegasus/man-2.1/

	-Kenar- (Kenji Arisawa)

	E-mail: arisawa@aichi-u.ac.jp

General rules
Dollar '$' is only one special symbol of Rit.
A dollar followed by:
variable
	Variable is a sequence of alpha or numeric or '_'.
	subset of environment variable.
'{'
	Rc script follows. the script continues up to '}'.
	The terminator '}' must be out of rc string and out of { .. } nest.
'\n'
	NL (new line) escape

Example 1	command execution
	A dollar followed by '{':
	You can write rc script in curly brace { }
	Date: ${date}
	Note that we have redundant empty line after this command;
	this comes from two subsequent '\n's:
		one from command and one from our this text line.
	Avoiding this problem we have:
	${date} continues nest line
	${date}$ continues same line.
Example 2	variable
	A dollar followed by alpha or numeric
	User: $user
	This is equivalent to
	User: ${echo -n $user}
Example 3		NL escape
	A dollar at the end of line is NL escape.
	Example: This line has NL escape $
	next line.
	Many rc command produce NL at the end
	We can avoid redundant NL by putting NL escape:
	${pwd}$
	is current working directory.
	${pwd}$$
	this line stays in $${pwd}$$ line.
Example 4	multi-lines
	Rit has full functionality with rc.
	For example Rit allows multi-line script:
	${book='Alice in Wonder Land'}$
	${echo -n 'echo test of multi-line:
	line1: Carrol''s book:
	line2: '$book'
	line3: and we can use { and } in rc strings' }
	Back slash new line escape in Rc command will work:
	${echo -n one\
	two }
Example 5	'if' statement
	We have 'if' statement:
	${
		if(~ $user arisawa)
			echo ARISAWA
		if not
			echo NOT
	}$
Example 6	braces in Rc
	Switch statement.
	Note that { } is included in this example.
	${switch($user){
		case arisawa
			echo ARISAWA
		case *
			echo NOT }}$
Example 7	comment in Rc command
	Comment continues up to NL as Rc does.
	${# This is a comment up to NL } this is also a part of comment
	# this is also a comment
	} # invisible
	${# comment line1 terminated by Rc NL escape\
	comment line2
	} # invisible
	$${# This isn't a comment but a part of text }
Example 8
	$0 is special, this is a file name currently processed.
	Dollar followed other characters is not a special. i.e.,
	$, $#
	are shown as it is.
Example 9
	Sequence of dollars are processed as follows:
	one dollar is simply discarded.
	$$$$home is equivalent to ${echo -n '$$$home'}
	$$$${not a rc script}
	$$$$
	is not a NL escape.
Note on termination
	${echo exit 'some message'>[1=2];exit} will terminate Rit.
	Rc function "quit" is predefined in Rit:
		fn quit {echo exit $1 >[1=2];exit}
	Simple Rc "exit" does not terminate Rit
	but next ${ } block will terminate Rit because of error.
	For example ${exit} ${} will terminate Rit.