GNU Guile 2.2.0

If I compare RMarkdown and org-mode, for example, org is strictly better for academic writing or anywhere else where internal cross-references are needed. Org isn't an astounding format, but it is quietly competent.

So it's stopped being an issue years ago!

You could force guile on everybody, just as e.g. perl5 did with their Test2 replacement, but not everybody will be happy with a 20% performance hit in the real world, and esp. when telling nobody about it. This would be pure marketing shit.

What is not mentioned in that thread (at least not in RMS' original message) is that what triggered his edict was that somebody extended gdb with Tcl as the extension language. This was an absolutely reasonable use case for Tcl - the lightweight syntax makes it perfect as an interactive, embedded scripting language.

This discussion led to the creation of Guile, the withering of Tcl support in gdb, and eventually the introduction of a gdb that used Guile as its extension language — in 2014, 20 years after RMS decided that the Tcl extension (which I believe pretty much worked already) was unacceptable.

Of course, as astute readers will already have guessed, Tcl was BSD licensed...

Robin Templeton also seems to be the one which finished off the elisp compatibility on Guile here so it's probably because he saw that as important to get first.

These days, some distros use lz and most use xz, probably mostly due to historical reasons.

So yes, being part of the GNU project is probably more of a cultural thing than an immediate practical advantage.

Cf. is an abbreviation of "confer" which is Latin for compare and is used to introduce material that should be compared to assertions made previously.

Viz. is an abbreviation of "vidilcet" which is Latin for "namely" or "as follows" and is used to indicate a more complete statement or example of something that has just been asserted, whereas e.g. precedes examples that illustrate a point.

Viz. and cf. are often confused, as in this case.

Are you saying this is inaccurate? Andy is far and away the top contributor, it's not even close. It really does seem to be a one man show.

This is my favorite example.

http://www.gigamonkeys.com/book/macros-standard-control-cons...

[Common Lisp's] DOLIST is similar to Perl's foreach or Python's for. Java added a similar kind of loop construct with the "enhanced" for loop in Java 1.5, as part of JSR-201.

Notice what a difference macros make. A Lisp programmer who notices a common pattern in their code can write a macro to give themselves a source-level abstraction of that pattern.

A Java programmer who notices the same pattern has to convince Sun that this particular abstraction is worth adding to the language. Then Sun has to publish a JSR and convene an industry-wide "expert group" to hash everything out. That process--according to Sun--takes an average of 18 months. After that, the compiler writers all have to go upgrade their compilers to support the new feature. And even once the Java programmer's favorite compiler supports the new version of Java, they probably still can't use the new feature until they're allowed to break source compatibility with older versions of Java.

So an annoyance that Common Lisp programmers can resolve for themselves within five minutes plagues Java programmers for years.

To create new syntax and be your own language designer. This is what macro systems allow for. Here's a very contrived and simple example. Guile comes with no equivalent of the `++` operator that we know from C, C++, etc. So in the event that we have some imperative code that is mutating a counter, we'd have to write something like this:

    (define counter 0)
    ;; do some stuff...
    (set! counter (+ counter 1))

    (define (++ n) (set! n (+ n 1)))
    (define counter 0)
    (++ counter)

    (define-syntax-rule (++ var) (set! var (+ var 1)))
    (define counter-a 0)
    (define counter-b 0)
    (++ counter-a)
    (++ counter-b)
    (++ counter-a)

The reason these syntactic abstractions are so easy to make is because of the homoiconic Lisp syntax. I hope this has made sense and is helpful. Moving on from this simple example, we can create entirely new languages that are embedded in Scheme if we wanted to, adding things that are too specific to a problem domain to ever be in the standard language's syntax but very useful for the problem we are trying to solve.

Lisp macros are something like C macros, chainsaws, hydrochloric acid, or anything else that's powerful-but-dangerous. This is to say that sometimes they are the one tool you have to use, but often they are unnecessary and should be avoided.

Coming up on ten years ago, I wrote this blog post on one of the dangers of Common Lisp style macros: http://www.mschaef.com/blog/tech/lisp/defmacro-coupling.html

Put succinctly, the problem I write about in the blog post is that macros are essentially always inlined into the output of the compiler. This has the effect of more tightly coupling the modules together than is evident in the surface syntax. (Note that macro invocation sites are syntactically indistinguishable from function invocation sites, which makes this problem worse.)

The upshot of this is what you'd expect: the extent of the logic encoded in macros should be minimized, with the macros translating the code pretty much straight away into something built on more functional abstractions.

This is not to say that Macros aren't useful... sometimes you _have_ to use them to achieve a goal. Just that they probably aren't as big a deal as might be expected given the amount of 'press' they get.

Lisp macros give meaning to syntax that doesn't previously have meaning. In this regard, they are the same as functions.

(foo (boonly) blarg) doesn't have any meaning because foo hasn't been defined.

We can fix that by writing a function foo. Then (boonly) and blarg have to be valid expressions and we are good.

Or we can make it mean something can by writing a macro foo. The macro foo is a function that will operate on the entire form (foo (boonly) blarg) and calculate a replacement for it. The Lisp form expander (a feature of the compiler or interpreter) will call the macro and accept its return value as the replacement for the macro call. Then, the replacement is scanned for more macros; the entire process removes all macros until all that is left is special operators and functions.

A practical example of a macro is the ANSI Common Lisp standard macro called loop which provides a syntax for iterating variables, stepping through collections, and taking various actions or gathering results:

  (loop for bit in '(0 3 7 13)
        for mask = (ash 1 bit)
        summing mask) -> 8329 

(Enter (Arne))

(Arne (Hello!) (Who are you?))

The above is actual code which makes Arne say two lines of text.

Essentially the Enter defines a new specialized control structure which is optimized for the task of defining lines of text for a character in an RPG to say.

This removes cognitive overhead while writing a scene: You only write what which character should say.

Essentially you invest into creating a better-fitting tool to simplify all following work. With Scheme you can take this further than with anything else — short of taking over the whole language implementation (which for example Facebook did with their new PHP implementations. With Guile you can take the path Facebook took, without first needing to be a multi-billion-dollar company). But as any other power, use this with care: You won’t want to make your code so much different from what other Schemers do that others have a hard time joining in.

¹: https://fosdem.org/2017/schedule/event/naturalscriptwritingg... — also see the video and the slides which show the difference between this syntax and examples from other methods, including one of my earlier tries with Python.

That can be utilized both at high level and low level. GOAL is a cool example: https://en.wikipedia.org/wiki/Game_Oriented_Assembly_Lisp. Basically you can express assembly code in LISP syntax and then you can create higher level constructs like if, while, for etc statements as macros composing these lower lever assembly instructions. Because data and code is the same in LISP that allowed Naughty Dog when they used GOAL on the Playstation 2, to swap chunks of code in and out of memory as needed easily to maintain larger levels than the competition. It is also something that allows you to change a running system. I believe there was a case of a malfunctioning satellite running LISP code, which was debugged and fixed while it was running. Shutting it down for fixing was not an option.

I would also add another benefit of only using parenthesis. It makes it really easy to make powerful tools for LISP. Have a look at s-expression based editing. Instead of working line by line, or word by word as we are used to with editors, these work with whole blocks of code at the time. Normal editor commands involve jumping word by word or line by line. with LISP editors you can view the code as a tree with keyboard commands for jumping between tree siblings, up to a parent or down to a child. Instead of selecting x number of lines or words, you can select a whole subtree and delete it, move it, duplicate it or whatever. I think they usually call it paredit. Here is an animated demonstration of how it works: http://danmidwood.com/content/2014/11/21/animated-paredit.ht...

Disclaimer: I never really got used to LISP myself. I think it is cool, but it was too big of a jump for me when I started from C++ background. However I feel more used to it now as I've programmed a lot in Julia which is LISP like but with more normal syntax. Also when I first checked out LISP I didn't understand the need to change the way you think about navigating and editing code. If you edit the way you edit normal code I think it easily gets confusing. You lose track of the parenthesis. I didn't know about stuff like paredit then.

Performance, macros are executed at compile time. Also, sometime the macro is easier to write that the equivalent non-macro code.

That's the whole syntax. So now you know how to program in LISP.

There's no statements in lisp, only the above expression repeated, which you can nest one in another, or sequence them one after another. They're called S-expressions.

For me, that simplicity is the first advantage. It's just very consistent and quick to learn. It also allows to embed everything together, like assign a value in an if condition.

The second big advantage, is that this syntax is very easily parsed into a list and can be easily changed programatically. Lisp lets you do that by defining macros.

A) It works by defining a function which takes the parsed code as an AST, and returns a modified AST. To transform the AST you have the full power of LISP availaible and some convenient operators that make it easier.

B) There's many benefits. Conceptually, it lets you change the evaluation order of code. Normally a function evaluates its arguments from left to right and then passes the resulting values to be evaluated by the function. 99% of the time this is what you want. But what if you want to short-circuit the evaluation of the arguments when one of them evaluates to say false. This would come in handy if writing the AND function. A macro allows you to do it. In other languages, you're given special operators for this kind of thing, but they're limited and you can not add new ones.

Another practical case is aspect oriented programming. Imagine you want to print the argument to all functions and all their return values. With a macro you can do this:

(print-steps (+ (- 100 23 price) (* 12 34 56 people))).

Print steps is able to inject a print statement at multiple code points, around each arguments and around every functions. Without a macro, you would have had to re-write all this manually, and then delete it again once you're done debugging. Some languages like Java give you a complicated framework which can do this to a certain extent, but aspect-J is a pre-processor, just like macros, it's just that the Java syntax makes this really complicated to implement, so you need a framework to do most of the work, or it's not practical.

C) That's up to you to decide. You don't ever have to write a single macro, and should only use them when they are needed and make sense. Now reading code with macros is trickier, because every macro could be a custom operator you have never seen before, or an aspect that does things you're not sure about. To me, this just becomes a thing of don't write crappy unreadable code. Which is true in all languages. I'd suggest teams standardize their macros, and document them well, so new members can quickly get familiar with your team's macros. Once familiar with a set of macros though, they make you a lot more productive and do make code more concise and even easier the read sometimes.