picol: A Tcl interpreter in 500 lines of code

(github.com)

64 points | by tosh 6 hours ago ago

39 comments

  • stevekemp 4 hours ago

    Sadly it seems the blog post that was released in the past is no longer available, but the wayback machine has a copy

    https://web.archive.org/web/20220303135439/https://oldblog.a...

    That provides background about the constraints/limitations in this code.

    • antirez 3 hours ago

      Restored. Recently I migrated all my stuff into a new server and missed to migrate the /pages of the old blog. Thanks.

  • seyz 2 hours ago

    Classic antirez. Does more in 500 LOC than most frameworks in 50k.

  • antirez 5 hours ago
  • JSR_FDED 5 hours ago

    I remember we had users at a chip foundry who were super deep into TCL. Is it still used anywhere else? Would you use it for a new project if you for instance already knew Python or Lua?

    • shawn_w 13 minutes ago

      I like tcl as an alternative to shell for any non-trivial scripts.

      And its coroutines + built in event loop makes for really nice seamless async style programming.

    • amelius 3 hours ago

      By the way, I'm guessing that Tcl was (is?) big in EDA because John Ousterhout also wrote the EDA tool Magic.

      https://en.wikipedia.org/wiki/Magic_(software)

    • catwell 5 hours ago

      Antirez (the author of this interpreter) uses it for the Redis test suite.

      Personally, I know Lua and Python very well but I still used TCL a few years ago for something very specific: using ODBC on Windows. I gave more details on the Lua mailing list here: http://lua-users.org/lists/lua-l/2021-01/msg00067.html

      • JSR_FDED 5 hours ago

        That was interesting to read. So in your case it came down to ecosystem depth, especially on Windows - where there was a TCL solution to talk ODBC, but the equivalent Lua functionality had issues on Windows.

    • smartmic 3 hours ago

      It is at the core of the SQLite test suite and also a first-class citizen in interfacing to it.

    • danhor 5 hours ago

      It's still the lingua-franca of ASIC/FPGA/Simulation, especially for scripting the tools.

      I think it's slowly being replaced there by Python, but it's very slow.

    • vodou 5 hours ago

      It is still used for operations procedures in, at least, European space industry. E.g., in mission control systems from Terma (CCS5 and TSC).

    • rausr 4 hours ago

      We've got Check Point Firewalls at work, and during updates I see lots of .tcl in the web UI.

    • sprash 4 hours ago

      Tcl/Tk to this day is the best tool to make GUI frontends for CLI applications. Besides that, in the past I used it in production for intranet database entry applications. It has since been replaced by Flask. In my opinion the higher complexity of the Flask version is no way justified and we should have kept the much simpler ~2k LOC Tcl/Tk solution.

      • WillAdams an hour ago

        What is the best and easiest to install binary distribution?

        I was looking into this for v9 and gave up on finding a binary which was:

        - easily found

        - agreed upon as the one to use

        - available for and easy to install on all three platforms

        Should I look again?

      • jhbadger 3 hours ago

        In the 1990s, entire GUI applications would be written in Tcl/Tk -- not just the frontend -- the entire thing.

      • fuzztester 3 hours ago

        >Tcl/Tk to this day is the best tool to make GUI frontends for CLI applications.

        Why? Please elaborate. I've heard others say this, but would like to know more.

        >Besides that, in the past I used it in production for intranet database entry applications.

        GUI apps?

        • sprash an hour ago

          > Why?

          CLI applications typically read text from stdin and write text to stdout. The tcl model of "everything is a string" makes exactly the right abstraction to create GUI frontends for CLI applications rapidly and keep them simple at the same time.

    • AceJohnny2 4 hours ago

      I'm looking to use TCL for an embedded platform, as the scripting shell. Its simplicity and small size is key, as is its easy integration with C.

  • iberator 4 hours ago

    best thing about TCL is easy syntax and that everything is a string :) Unique and simple and easy language with very slow changes.

    Something like Python in good old days of 2.x before young internet javasceipt devs started pouring A LOT of new features to the language (feature creep).

    Nowadays Python is so complex and flooded with ex C, C++, Java, JavaScript, Haskell programmers adding so many features, so fast that it's impossible to follow and understand them :(

    Languages should not evolve on that rate. No time to master it :(

    /rant

    • pjmlp 2 hours ago

      Tcl has stopped being everything a string with the release of Tcl 8.0 and bytecode engine.

      > In earlier versions of Tcl, strings were used as a universal representation; in Tcl 8.0 strings are replaced with Tcl_Obj structures ("objects") that can hold both a string value and an internal form such as a binary integer or compiled bytecodes.

      http://www.ira.inaf.it/Computing/manuals/tcl/man-8.0/Changes...

      I remember this quite well, because as part of the core team tasked with writing native C extensions, the migration to Tcl 8 had quite an impact on our code.

      I learned Python with version 1.6, and have a few O'Reilley books proving the point the language wasn't really that simple, those that never bothered reading the reference manuals end-to-end though it was.

    • robinsonb5 3 hours ago

      There's certainly something to be said for stable, uncomplicated and minimalist tooling that wont evolve out from under you and leave you with something that won't just-work five years from now.

      I guess that's why Tcl is so popular in the EDA arena. I can stick some custom JTAG tooling in a Cyclone II design and talk to it by Tcl-scripting the 15-year-old software - and be confident that the same code (both in the FPGA and on the host computer) would work with the latest software and a current device.

      Having said that, Tcl's not entirely free of compatibility and fragmentation frustrations: I sometimes wish that OpenOCD used full-fat Tcl rather than JimTcl, just so that I could make use of Tk. Being able to plot a histogram of data collected from the FPGA or make clickable buttons to trigger events is very useful.

    • tonyedgecombe 4 hours ago

      I agree, so much for the benevolent dictator idea.

    • Pay08 4 hours ago

      That's certainly a take...

    • IshKebab 4 hours ago

      > best thing about TCL is easy syntax and that everything is a string :)

      What? That's the worst thing about TCL.

      • antirez 2 hours ago

        It depends on the use case. For instance you open a socket, write there any value you have without serialization, read it in the other side, data transfer done.

        • petcat 2 hours ago

          The convenience of not having to marshal data over a network is certainly a use case. But I'll admit that two of the worst programs I ever saw were written in Perl and TCL. Somehow just a big jumble of inscrutable regexes.

          When "everything is a string" then you have no choice but to literally treat everything as a string. Painful. Very cool project though.

          • graemep 41 minutes ago

            That sounds more like someone who over-uses regexes - the developer is the problem, not the language

            TCL has a lot of options for manipulating strings - take a look at just the built in string command for a start: https://www.tcl-lang.org/man/tcl8.4/TclCmd/string.htm

            I have seen terrible code in Python, C, and more.

      • bmacho 3 hours ago

        It's only the interface that is of a string. An array is a list of strings with space between, but only for the programmer. The runtime is free to use an actual array.

        • IshKebab an hour ago

          I'm aware. It's awful because of the implications for the programmer, not the runtime.

      • iberator 4 hours ago

        I love it. Living proof that languages doesn't need forced types.

        Data is Data. It's kinda object programming as visioned in the 70".

        So easy and trivial language.

        • IshKebab an hour ago

          > Living proof that languages doesn't need forced types.

          The opposite surely? TCL is practically dead, and only lingers on in the EDA industry (which has zero taste). Virtually every successful language today has at least a few different basic types for numbers, arrays, strings, maps and so on.

          • bmacho an hour ago

            Tcl has these types as well. They are special strings.

            Number: string of digits. List: strings separated by space. Dictionary: key value pairs in a list.

  • anthk 5 hours ago

    JimTCL has more features and it's almost as small.