HISTORY
This was originally written as a perl5 script. Rather than doing bootstrapping, I foolishly decided it would be fun to write the parser IN parrot assembly, esp. as this would help implementing "eval" and "proc" (Of course, in retrospect, I really wish I had kept with the bootstrapping effort, as I think it would have generated usable results sooner.
OVERVIEW
This is a from-scratch implementation, based primarily on the tcl man page(s), and the cvs-current test suite for tcl.
Another interesting project would have been to modify the tcl source and have it generate parrot directly. Many people smarter than I am have declared this hard, so I'm rather happy I'm working on it this way. (Apparently Tcl's bytecode engine is very optimized for Tcl (big surprise). So, converting the tcl-specific bytecodes there to parrot would be a big deal.)
RUNNING TCL
Generated Files
When you make tcl, you're generating several files:
- lib/tcllib.pbc
-
This file is used to load all the various commands, ops, etc. into the appropriate namespaces, as well as declare and register the TCL compiler for the
compile
opcode.This file is actually built in two steps. The first step uses
tcl.pl
to generatelib/tcllib.pir
, usingtcl.pir_template
as a template. The file is basically passed through unchanged, except for a few${ }
-style substitutions.INCLUDES
make sure all the required.pir
files are included properly. It adds aHEADER
, and removes anyXXX
comments. - tcl.pbc
-
This is roughly equivalent to
tclsh
- It takes the command line arguments (currently, the name of the file you wish to parse), and reads in the file, and uses the tcl library to parse those contents as tcl. You can also specify command line options to be used with this bytecode file.
Classes
The classes are not user-visible, but are internal helper classes designed to simplify the parser/interpreter. They are written in PIR and are in lib
. All the helper classes provide a compile
method, which can be invoked by the top level compiler, or by a container class. For example, in TclConst
, the compilation is a very straightforward register load, while TclCommandList
compiles each of the TclCommand
s it contains, which in turn compile their arguments, and their method name, and setup an invocation of the PIR subroutine that corresponds to the tcl proc or builtin.
- TclCommand
-
A class representing a Tcl command made up of a name and arguments.
- TclCommandList
-
A list of TclCommands used to represent a body of code. This returns the value of the last command.
- TclConst
-
A constant Tcl value created during parsing.
- TclVar
-
A class representing Tcl variables.
- TclWord
-
A TclWord handles the concatenation of arguments. For instance, given
puts ab$c
the parser will generate a
TclWord
containing anTclConst
==ab
and aTclVar
==c
. When compiled, aTclWord
compiles each of its elements and concatenates the results.
PMCS
The Tcl PMCs (Parrot Magic Cookies) are the user visible data types. These live in the *.pmc
files in classes/
. They are compiled into a dynamically loadable library which is loaded with the .HLL
directive (HLL stands for High Level Language). Most of the functionality associated with these PMCS is derived from the base parrot classes, except as noted below.
- TclString
-
Scalar string, with an override for the boolean truth values.
- TclInt
-
Scalar integer, with an override for various math. (For example, parrot Integers automatically promote to float division, while Tcl does not.)
- TclFloat
-
Scalar float, with an override of the stringification: Tcl floats are somewhat unusual compared to other parrot HLLs in that integer-valued floats stringify with a trailing
.0
. - TclList
-
Ordered container, corresponding to values generated by the
[list]
builtin. Overrides the default stringification provided by parrot Arrays. - TclArray
-
Hash like container, corresponding to values created with the
[array]
builtin. - TclObject
-
A virtual type, which is used to provide some shimmer (aka morph) methods common to all the scalar value types.
TESTS
To run the test suite, make test
. If you want to also get output from the TODO tests, make devtest
instead. This is NOT the tcl test suite. No failures are expected.
To run the tcl test suite, type "make tcl-test". This will checkout the latest cvs copy of the tests from the tcl repository and run them. Warning:
- 1 Slow
-
There are a lot of tests, and we setup and breakdown an instance of parrot for *each* test we try to run.
- 2 Incomplete
-
We convert the tests to use Perl's TAP instead of running them natively. The conversion process is flawed, and we don't claim to implement 100% of Tcl yet anyway. Expect a low pass rate.
EXAMPLES
There are examples in the examples
directory that are vaguely more interesting. Change to that directory and type make
for directions.