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:

runtime/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 several steps. First, all the templated commands (src/builtin/*.tmt) are converted to PIR. Next, runtime/builtins.pir is generated from all the pir files in src/builtin/ and runtime/builtin. This file is then included by tcllib.pir and compiled to tcllib.pbc.

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.

src/grammar/expr/pge2past.pir

src/grammar/expr/past2pir.pir

src/grammar/expr/expression.pir

This PIR files are generated from their corresponding .tg and .pg files. These grammar files allow us to use PGE's implementation of perl6 rules to more simply specify our parsing rules. At the moment, only the [expr] rules are used. This might eventually be extended to replace the entire parsing system used by tcl, which was originally hand-rolled in PIR.

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 src/classes. 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 TclCommands 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 an TclConst==ab and a TclVar==c. When compiled, a TclWord 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 src/pmc/. 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. Occasional failures are suspected against svn-head; there should be no failures in a released version, however.

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.