Provided by: tcllib_1.17-dfsg-1_all 
NAME
wip - Word Interpreter
SYNOPSIS
package require Tcl 8.4
package require wip ?2.2?
package require snit ?1.3?
package require struct::set
::wip wipName engine arg...
def name
def name method_prefix
wipName option ?arg arg ...?
wip::dsl ?suffix?
wipName def name ?method_prefix?
wipName defl names
wipName defd dict
wipName deflva name...
wipName defdva (name method_prefix)...
wipName undefl names
wipName undefva name...
wipName unknown cmdprefix
wipName runl wordlist
wipName run word...
wipName run_next
wipName run_next_while acceptable
wipName run_next_until rejected
wipName run_next_if acceptable
wipName run_next_ifnot rejected
wipName next
wipName peek
wipName peekall
wipName insertl at wordlist
wipName replacel wordlist
wipName pushl wordlist
wipName addl wordlist
wipName insert at word...
wipName replace word...
wipName push word...
wipName add word...
_________________________________________________________________________________________________
DESCRIPTION
This package provides a micro interpreter for lists of words. Domain specific languages
based on this will have a bit of a Forth feel, with the input stream segmented into words
and any other structuring left to whatever the language desired. Note that we have here in
essence only the core dispatch loop, and no actual commands whatsoever, making this
definitely only a Forth feel and not an actual Forth.
The idea is derived from Colin McCormack's treeql processor, modified to require less
boiler plate within the command implementations, at the expense of, likely, execution
speed. In addition the interface between processor core and commands is more complex too.
GENERAL BEHAVIOUR
Word interpreters have a mappping from the names of the language commands they shall
recognize to the methods in the engine to invoke for them, and possibly fixed arguments
for these methods. This mapping is largely static, however it is possible to change it
during the execution of a word list (= program).
At the time a language command is defined the word interpreter will use snit's
introspection capabilities to determine the number of arguments expected by the method of
the egnine, and together with the number of fixed arguments supplied in the method prefix
of the mapping it then knows how many arguments the language command is expecting. This is
the command's arity. Variable-argument methods (i.e. with the last argument named args)
are not allowed and will cause the word interpreter to throw an error at definition time.
Note that while I said snit's abilities the engine object can be written in any way, as
long as it understands the method info args, which takes a method name and returns the
list of arguments for that method.
When executing a list of words (aka program) the first word is always taken as the name of
a language command, and the next words as its arguments, per the arity of the command.
Command and argument words are removed from the list and then associated method of the
engine is executed with the argument words. The process then repeats using the then-first
word of the list.
Note that the methods implementing the language commands may have full access to the list
of words and are allowed to manipulate as they see fit.
[1] This means, for example, that while we cannot specify variable-argument methods
directly they can consume words after their fixed arguments before returning to the
execution loop. This may be under the control of their fixed arguments.
[2] Another possibility is the use of method run_next and its variants to execute
commands coming after the current command, changing the order of execution.
[3] Execution can be further changed by use of the program accessor methods which allow
a command implementation to modify the remaining list of words (insert, replace,
prepend, append words) without executing them immediately.
[4] At last the basic run methods save and restore an existing list of words when used,
enabling recursive use from within command implementations.
CLASS API
The main command of the package is:
::wip wipName engine arg...
The command creates a new word interpreter object with an associated global Tcl
command whose name is wipName. If however the string %AUTO% was used as object name
the package will generate its own unique name for the object.
The engine is the object the word interpreter will dispatch all recognized commands
to, and the arguments are a word list which defines an initial mapping from
language words to engine methods.
The recognized language of this word list is
def name
Defines name as command of the language, to be mapped to a method of the
engine having the same name.
def name method_prefix
Defines name as command of the language, to be mapped to the method of the
engine named in the method_prefix.
The returned command may be used to invoke various operations on the object. It has the
following general form:
wipName option ?arg arg ...?
Option and the args determine the exact behavior of the command.
The package additionally exports the command:
wip::dsl ?suffix?
This command is for use within snit types which wish to use one or more wip
interpreters as a component. Use within the type definition installs most of the
boilerplate needed to setup and use a word interpreter.
It installs a component named wip, and a method wip_setup for initializing it. This
method has to be called from within the constructor of the type using the word
interpreter. If further installs a series of procedures which make the object API
of the word interpreter directly available to the type's methods, without having to
specify the component.
Note that this does and cannot install the language to interpret, i.e. the mapping
from words to engine methods.
It is possible to instantiate multiple word interpreter components within a type by
using different suffices as arguments to the command. In that case the name of the
component changes to ´wip_$suffix', the setup command becomes ´wip_$suffix_setup'
and all the procedures also get the suffix ´_$suffix'.
OBJECT API
The following commands are possible for word interpreter objects:
wipName def name ?method_prefix?
Defines a language command name and maps it to the method named in the engine's
method_prefix. If the method_prefix name is not specified it is simply the name of
the language command.
wipName defl names
Defines a series of language commands, specified through the list of names, all of
which are mapped to engine methods of the same name.
wipName defd dict
Defines a series of language commands, specified through the dictionary dict of
names and method prefixes.
wipName deflva name...
As method defl, however the list of names is specified through multiple arguments.
wipName defdva (name method_prefix)...
As method defd, however the dictionary of names and method prefixes is specified
through multiple arguments.
wipName undefl names
Removes the named series of language commands from the mapping.
wipName undefva name...
As method undefl, however the list of names is specified through multiple
arguments.
wipName unknown cmdprefix
Sets the handler for unknown words to cmdprefix. This command prefix takes one
argument, the current word, and either throws some error, or returns the result of
executing the word, as defined by the handler. The default handler simply throws an
error.
wipName runl wordlist
Treats the list of words in wordlist as a program and executes the contained
command one by one. The result of the command executed last is returned as the
result of this command.
The wordlist is stored in the object for access by the other run-methods, and the
general program accessor methods (see below). A previously stored wordlist is saved
during the execution of this method and restored before it returns. This enables
the recursive execution of word lists within word lists.
wipName run word...
As method runl, however the list of words to execute is specified through multiple
arguments.
wipName run_next
Low-level method. Determines the next word in the list of words, and its arguments,
and then executes it. The result of the executed word is the result of this method.
Exposed for use within command implementations. The methods run and runl use it to
execute words until their word list is exhausted.
wipName run_next_while acceptable
Low-level method. Invokes the method run_next as long as the next word is in the
set of acceptable words, and the program is not empty. The result of the command
executed last is returned as the result of this command.
Exposed for use within command implementations to change the order of execution.
wipName run_next_until rejected
Low-level method. Invokes the method run_next until the next word is in the set of
rejected words, and the program is not empty. The result of the command executed
last is returned as the result of this command.
Exposed for use within command implementations to change the order of execution.
wipName run_next_if acceptable
Low-level method. Invokes the method run_next if the next word is in the set of
acceptable words, and the program is not empty. The result of the command executed
last is returned as the result of this command.
Exposed for use within command implementations to change the order of execution.
wipName run_next_ifnot rejected
Low-level method. Invokes the method run_next if the next word is not in the set of
rejected words, and the program is not empty. The result of the command executed
last is returned as the result of this command.
Exposed for use within command implementations to change the order of execution.
wipName next
Returns the next word in the programm. The word is also removed.
wipName peek
Returns the next word in the programm without removing it
wipName peekall
Returns the remaining programm in toto.
wipName insertl at wordlist
Basic programm accessor method. Inserts the specified wordlist into the program,
just before the word at position at. Positions are counted from zero.
wipName replacel wordlist
Basic programm accessor method. Replaces the whole stored program with the
specified wordlist.
wipName pushl wordlist
Program accessor method. The specified wordlist is added to the front of the
remaining program. Equivalent to
$wip insertl 0 $wordlist
wipName addl wordlist
Program accessor method. The specified wordlist is appended at the end of the
remaining program. Equivalent to
$wip insertl end $wordlist
wipName insert at word...
Like method insertl, except the words are specified through multiple arguments.
wipName replace word...
Like method setl, except the words are specified through multiple arguments.
wipName push word...
Like method pushl, except the words are specified through multiple arguments.
wipName add word...
Like method addl, except the words are specified through multiple arguments.
EXAMPLES
No examples yet.
BUGS, IDEAS, FEEDBACK
This document, and the package it describes, will undoubtedly contain bugs and other
problems. Please report such in the category wip of the Tcllib Trackers
[http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for enhancements you
may have for either package and/or documentation.
KEYWORDS
interpreter, list, word
CATEGORY
Programming tools
COPYRIGHT
Copyright (c) 2007-2010 Andreas Kupries <andreas_kupries@users.sourceforge.net>