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Curly-infix and readable LispCurly-infix and readable LispPosted Dec 3, 2012 22:08 UTC (Mon) by proski (subscriber, #104)In reply to: Curly-infix and readable Lisp by david.a.wheeler Parent article: GNU Guile 2.0.7 released As a user of GNU Lilypond, I have to admit that the learning curve for Guile has been rather steep for me. The infix syntax would have mitigated the problem somewhat. In addition to having more readable syntax, it would be nice to have a way to warn about potential mistakes, such as unused variables. I'm so used to compiler warnings in C that not having them in Guile would make me quite nervous when writing advanced code.
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Curly-infix and readable Lisp Posted Dec 4, 2012 15:34 UTC (Tue) by dakas (guest, #88146) [Link] The infix syntax would have mitigated the problem somewhat.I doubt it. It is like imagining that a unidirectional word-by-word translator will enable you to write poetry in a language you don't know. You'll probably learn more about its grammar's dark corners than you ever wanted to know when trying to navigate by error messages. Driving through a superficial mechanical remapping layer will make things more rather than less baffling: the familiarity you hope for is not more than a front, and understanding just when this front does what you expect, and when it fails for what reason for what purposes, will require a deeper understanding than just writing in Scheme in the first place would. And you'll have a harder time communicating with others. Already trivial things like using totally different formatting and placement of parens cause code to become less readable to coworkers, and worse to manage for simple text-based replacements. An infix layer is not going to help, in particular since it does not really have a corresponding print form, so all output and all intermediate forms will look unfamiliar. Don't get me wrong: it is great that you can do this sort of transformation game in Scheme, and it is a nice exercise and proof of concept. But I don't consider it of practical relevance. It will be a project a number of people will enjoy and improve, but it will get used for very little "serious work" (TM), basically by almost nobody from the purported target clientele of people feeling unable to get their head wrapped around prefix syntax, and will eventually peter out.
Curly-infix and readable Lisp Posted Dec 4, 2012 17:09 UTC (Tue) by david.a.wheeler (guest, #72896) [Link] Poster says: the familiarity you hope for is not more than a front, and understanding just when this front does what you expect... will require a deeper understanding than just writing in Scheme in the first place would. The curly-infix notation is defined in terms of underlying list notations, so this fear is unwarranted. In Lisp, 'x is just an abbreviation for (quote x); this is just another abbreviation. It's important to note that curly-infix, unlike past infix notations, does not lose the Lisp advantages of homoiconicity and genericity; for details, see the SRFI-105 specification or the "readable" project materials. And you'll have a harder time communicating with others. Quite the reverse. If you've taken high school math, you know what infix notation is, so infix notation makes it easier to communicate with others. Infix notation isn't going away; ALL people, programmers or not, are trained to use infix operations with typical arithmetic operations, and failing to support infix notation is a real problem for Lisps. ... An infix layer is not going to help, in particular since it does not really have a corresponding print form, so all output and all intermediate forms will look unfamiliar. It has a corresponding print form, namely, {...}. ... it will get used for very little "serious work" (TM), basically by almost nobody from the purported target clientele of people feeling unable to get their head wrapped around prefix syntax, and will eventually peter out. Scheme and Common Lisp are often avoided today for new "serious work", period. I believe one of the reasons for this is that their syntax is repugnant to most developers. It's not a matter of not being able to get their head "wrapped around" a prefix system; the prefix system is easy. Many, many Scheme and Common Lisp systems have added infix notations, but they are all incompatible with each other. If we can get a SINGLE notation adopted by many such systems, that problem disappears.
Curly-infix and readable Lisp Posted Dec 4, 2012 19:03 UTC (Tue) by dakas (guest, #88146) [Link]
I have seen my fair share of trying to make a language/system appear like something else. An alternative read syntax does not buy you an alternative output syntax or alternative data structures. You'll either get
'#{ 3 + 4 } => (+ 3 4) or '(+ 3 4) => #{ 3 + 4 } and if you get the latter, it will be hard to figure the "flipping point" where #{ } will get used over normal list syntax in output, and where not.
And frankly, things like
Lisp forms are self-descriptive simple data structures, easily juggled around and interpreted by programs and macros. That's why we put up with this highly nested interpunction-sparse mess of a "language" (can you call something a language which just interprets the read form of data structures?) in the first place, and infix does not change this fundamental problem of having the whole nesting of the underlying data structure exposed.
Actually, not the whole. We are likely glad not to have to write out
But conversion to infix is a different beast than converting a conventional arrangement of dotted pairs to list syntax.
Curly-infix and readable Lisp Posted Dec 4, 2012 21:03 UTC (Tue) by david.a.wheeler (guest, #72896) [Link] Poster wrote: Lisp forms are self-descriptive simple data structures, easily juggled around and interpreted by programs and macros... infix does not change this fundamental problem of having the whole nesting of the underlying data structure exposed. Actually, not the whole. We are likely glad not to have to write out (+ . (3 . (4 . (5 . ())))) => 12 and instead have an alternative in- and output form for this automatically. But conversion to infix is a different beast than converting a conventional arrangement of dotted pairs to list syntax. I think that's the core of the disagreement. Unlike you, I believe that infix can be easily considered - and reasoned about - as just another abbreviation in Lisp-based languages. As you noted above, Lisp users are already used to other much more complex abbreviations, and abbreviations make common cases easier to deal with. In curly-infix, {AAA op BBB op CCC ...} is just a new abbreviation for (op AAA BBB CCC ...). That's all, it's just another abbreviation. A curly-infix user needs to be aware that this is an abbreviation, but it's really no big deal. It takes about 10 minutes or so to get used to it, and it works for any operation at all. And the payoff is big; many people prefer to use infix notation for arithmetic, comparisons, and so on. This notation really helps when communicating with others. Today's software is typically developed by many people, and in the case of open source software, being able to read others' code is key. Thus, the Lisp expression "(car '{a + b + c})" will evaluate to "+", because {a + b + c} is another way to write the list (+ a b c), and "car" returns the first item in a list. Sure, it's odd when you've never seen this before, but it's actually easy to learn. All you have to remember is that "{...}" presents a list in infix order instead of the straightforward order, and thus, you need to look at the infix position to find the operator. Because there are no precedence rules (by intent), there's no possibility of the complex reasoning that I think you're concerned about, and the whole thing is really easy to learn. Most software developers would prefer to be able to write {{a * b} - c} instead of having to write (- (* a b) c). Let's give them the tools they actually want.
Curly-infix and readable Lisp Posted Dec 5, 2012 9:59 UTC (Wed) by dakas (guest, #88146) [Link] Most software developers would prefer to be able to write {{a * b} - c} instead of having to write (- (* a b) c). Let's give them the tools they actually want.It is a common mistake to confuse "what they ask for" with "what they want". Its designers being aware of that difference and refusing a lot of those requests is probably one of the most important things giving Lua its clout. It is the task of the language designer to consolidate the (not necessarily consistent) specifications into a coherent whole. And if the requirement is "a language designed around infix notation", the answer is not Scheme. It may be possible to implement an answer nicely in Scheme, but that just means that Scheme is a good tool for the job, not that it is the job itself. If you asked Leonardo da Vinci for a picture of a warrior with a helmet, it is unlikely that he would delivered the Mona Lisa with a mustache and helmet. There is a book "Numerical Recipes" with code written in Fortran. Fortran is not really all that popular any more, so there had been a followup "Numerical Recipes in C". The array indices in that book start at 1, the indexing is row-first, and the syntax used for a(i,j) is a[i][j] by allocating for each matrix a row pointer array, and separate arrays for each row, all the time leaving index 0 unoccupied. That's a similar kind of "giving them tools they actually want". If my job were to do numerical work in C, I'd get the Fortran book and go from there. Ultimately, I have to talk to the computer, and make sense to it, and different languages have different inherent means to make sense. In this case, it would mean a sense-preserving translation into C (requiring explicit index arithmetic, or nowadays, C9x-like variable-dimensioned multidimensional arrays) or punting and using extern "Fortran" ...If somebody asked me for Swedish poetry, I would not propose Shell I cumpere-a zeee-a tu a soommer's dey? Bork Bork Bork!
Curly-infix and readable Lisp Posted Dec 5, 2012 11:56 UTC (Wed) by Zack (guest, #37335) [Link]
I think I understand -- and share -- your point of view. But due to the nature of scheme people *will* inevitably try and "fix" the prefix notation again and again, so you might as well have an SFRI for it so people can at least consistenly try to make the same mistake.
I also believe it's going to end up fairly useless for actual programming, but specifically in the case of guile -- as an embedded extension language -- I can see a valid usecase. That is: people copying, pasting and minimally modifying (configuration) snippets they found somewhere, without having to think about syntax or programming.
It's a mistake to ignore the customer Posted Dec 5, 2012 20:12 UTC (Wed) by david.a.wheeler (guest, #72896) [Link] Poster says: It is a common mistake to confuse "what they ask for" with "what they want..." Sure, but it is an even more common mistake to ignore repeated, strongly-stated requests from many customers. Eventually customers will move on to someone who listens to them instead. Which is what's happened to Scheme, Common Lisp, and so on; few people use them for serious new projects. After all, even 1K BASICs manage to support infix. A good designer provides what the customer wants, perhaps not exactly what they asked for, but that's because the designer deeply figures out what the customer *really* wanted and provides it. That's not the case at all here; software developers know very well what infix looks like. (- (* a b) c) is not infix. When they say, "I want/miss infix", saying "Lisp executes with prefix notation" doesn't deal with their request at all. if the requirement is "a language designed around infix notation", the answer is not Scheme.". In other words, Scheme fails to meet most developers' minimum requirements for a "practical" language. To me, that statement describes a *problem*, not something good or fundamental. The curly-infix notation fixes an old, well-known bug. I'd add that no language is "designed around infix notation" - infix is typically a small surface syntax issue. You cannot say "Scheme's design means it is not possible to add infix", because it has been done. It's true that past infix approaches lost Scheme's homoiconicity and generality, which is part of why they haven't been accepted. But curly-infix doesn't have those problems, so that argument is gone. "We've never solved that problem before" is not a good argument for ignoring a problem. I think we'll just have to agree to disagree on this.
It's a mistake to ignore the customer Posted Dec 6, 2012 0:28 UTC (Thu) by dvdeug (subscriber, #10998) [Link]
I don't understand the problem this is trying to fix. Is there really a huge audience of people who would wrap their minds around Scheme if only it supported an infix notation? The illusion that this is an infix language is going to disappear the instant you have to look at anyone else's code, even the most trivial. If you have to look up something in a manual, any non-trivial example will force you to figure out the original syntax.
The Bourne shell code uses the C preprocessor to look like Algol 68. I don't believe anyone who had to maintain it was amused.
I don't know that most developers care about superficial syntax when they're looking for a practical language. (And if so, you're completely misusing brackets there, as they aren't being used like in C.)
It's a mistake to ignore the customer Posted Dec 6, 2012 15:18 UTC (Thu) by david.a.wheeler (guest, #72896) [Link] First, a few quotes:
Now a few replies...
The illusion that this is an infix language is going to disappear the instant you have to look at anyone else's code, even the most trivial. There is no such thing as an "infix language". There are simply programming languages, nearly all of which allow the use of infix notation. Internally many language implementations store constructs in some sort of abstract syntax tree; does that make them "abstract syntax tree languages"? Is there really a huge audience of people who would wrap their minds around Scheme if only it supported an infix notation? I would argue the other way. There is a huge audience of people who will never consider Scheme seriously as long as it fails to support notation that 1K BASICs manage. And it's not just for "outsiders"; as noted above, some current LISPers want to use infix too.
If you have to look up something in a manual, any non-trivial example will force you to figure out the original syntax. There is no "figuring out"; I expect developers to learn the underlying traditional Lisp notation, and then learn that there's a new abbreviation for some common cases. Scheme developers already need to know other abbreviations to be effective. For example, 'x means (quote x). Are you suggesting that developers cannot follow code in a manual if it says (quote x)? Curly-infix is just another abbreviation. Python developers actually have to learn many more abbreviations, by the way; there's no evidence that this short ruleset causes any hardship. I don't know that most developers care about superficial syntax when they're looking for a practical language. I think you're wrong on this point. I think most developers do care about surface syntax. Surface syntax matters, because you have to read a lot of code when developing. If the code is hard to read, you won't want to do it. Python has caught on in many places precisely because it has good "superficial" syntax. By the way, "superficial" is misleading; it's actually tricky to create really good surface syntax. If you didn't care about superficial syntax, why are you complaining about curly-infix? It is, fundamentally, a surface syntax. Lisp fails many users and potential users because its syntax ossified in the late 1950s / early 1960s. Even its original developer (McCarthy) thought Lisp notation had many problems as a programming notation. It's been over 50 years... it's time to fix its most well-known problems.
It's a mistake to ignore the customer Posted Dec 6, 2012 19:39 UTC (Thu) by dvdeug (subscriber, #10998) [Link]
You're adding syntactical complexity. You keep referring to Python, which has a rule "There should be one--and preferably only one--obvious way to do it." It's not going to make it make it any easier to read existing code, nor access existing Scheme books or tutorials.
"There is a huge audience of people who will never consider Scheme seriously as long as it fails to support notation that 1K BASICs manage." is hard to take seriously. For one, where's my PEEKs and POKEs? For another, it's said so many times; if we just added this feature, everyone would jump all over our tool. Changing (+ 4 7) to {4 + 7} is not going change anything for most people.
If you really think that it will be useful to existing programmers, then perhaps it will be a useful feature, but it's tacking on additional duplicate syntax, not fundamentally fixing any problems.
It's a mistake to ignore the customer Posted Dec 7, 2012 15:01 UTC (Fri) by david.a.wheeler (guest, #72896) [Link] Poster said: You're adding syntactical complexity. You keep referring to Python, which has a rule "There should be one--and preferably only one--obvious way to do it." Is 'x okay? After all, that's just a syntactic complexity for (quote x). I'm proposing another abbreviation for a common case. Funny you should mention Python. Python, of course, already has two representations for arithmetic operations, prefix and infix, if you want to create types that support infix operators. The Python infix operators are simply an abbreviation for the prefix operators, when you use them this way, e.g., infix "+" is an abbreviation for "__add__". See the Python special names for more. Many people are unaware that Python supports prefix notation in this case, because the infix notation is what users expect and want to use.
It's a mistake to ignore the customer Posted Dec 7, 2012 19:52 UTC (Fri) by dvdeug (subscriber, #10998) [Link]
And personally I think it's an inelegance that quote exists at all.
I think you're misstating the cause; the people who are unaware that Python supports prefix notation in this case are unaware because it's obscure and rarely used outside operator overloading, which is in part because __add__ is seriously more clunky then +. If the notation were + (a, b) and a __add__ b then people would use the prefix notation more. Moreover, people being unaware of the prefix notation means there's for most purposes only one notation, with __add__ and friends existing solely for operator overloading. (It would have been more elegant to extend the characters available for function names.) You're setting up two competing syntaxes, and the arguably more friendly one is not the one used for 35 years in Scheme and since the dawn of time in Lisp. Either the new one will see little to no use, or both will be used.
It's a mistake to ignore the customer Posted Dec 10, 2012 2:22 UTC (Mon) by david.a.wheeler (guest, #72896) [Link] Poster said: personally I think it's an inelegance that quote exists at all. I think that is an extremely small minority position. I think most people are happy to have abbreviations for common situations.
If the notation were + (a, b) and a __add__ b then people would use the prefix notation more. Actually, I think people just wouldn't use the language at all, if those were your only options. I believe that for many developers, infix using symbols like "+" is a "bare minimum" requirement for a programming language. It matters how code looks, it really does. You're setting up two competing syntaxes, and the arguably more friendly one is not the one used for 35 years in Scheme and since the dawn of time in Lisp. Either the new one will see little to no use, or both will be used. If a notation is more friendly, why should people object to it? My hope is that both will be used, and that isn't a problem. People see (quote x) and 'x all the time, it hasn't hurt them.
It's a mistake to ignore the customer Posted Dec 12, 2012 13:09 UTC (Wed) by HelloWorld (guest, #56129) [Link]
> If the notation were + (a, b) and a __add__ b then people would use the prefix notation more.
Bollocks. In Haskell, you can use (+) a b instead of a + b, but nobody actually does that. The only reason the (+) syntax exists is to make it possible to pass + to a higher-order function.
It's a mistake to ignore the customer Posted Dec 13, 2012 1:19 UTC (Thu) by mathstuf (subscriber, #69389) [Link]
Right, but it's closer to the question: Given:
> (+) a b
and
> a `add` b
as the "only" options, which would be more popular?
It's a mistake to ignore the customer Posted Dec 13, 2012 1:29 UTC (Thu) by mpr22 (subscriber, #60784) [Link] I'd go for option (c) Find the person who is requiring me to use this language clearly designed by either a parodist or a malicious idiot, and require them to explain to me in less than 150 syllables why I have to put up with it.
It's a mistake to ignore the customer Posted Dec 13, 2012 1:36 UTC (Thu) by mathstuf (subscriber, #69389) [Link]
Ah, yes. I forgot that option :) . That's how I feel with the class/method names people tend to use in Java… Biggest thing it's missing is a "typedef" equivalent, IMO.
It's a mistake to ignore the customer Posted Dec 13, 2012 21:17 UTC (Thu) by mirabilos (subscriber, #84359) [Link]
Urgh. U+0060 should never be used. It should really have been a combining character, but ASCII doesn’t really have them. See also: http://www.cl.cam.ac.uk/~mgk25/ucs/apostrophe.html
It's a mistake to ignore the customer Posted Dec 12, 2012 13:56 UTC (Wed) by mpr22 (subscriber, #60784) [Link] If the notation were + (a, b) and a __add__ b then people would use the prefix notation more. Fortunately, programming languages seldom (INTERCAL doesn't count, being a parody) display such high levels of overt malice in their design, and such an arrangement could not (at least in our world where infix notation arithmetic is the norm) plausibly be the product of mere stupidity or laziness.
More quotes showing that readable syntax matters Posted Dec 6, 2012 16:05 UTC (Thu) by david.a.wheeler (guest, #72896) [Link] Here are some more relevant quotes showing that surface syntax matters to developers:
It's a mistake to ignore the customer Posted Dec 6, 2012 15:21 UTC (Thu) by jezuch (subscriber, #52988) [Link]
> After all, even 1K BASICs manage to support infix.
What I don't understand is why infix is so important. The only advantage of it I can think of is familiarity; in all other respects it's inferior to prefix and suffix notations. IMVHO, of course, but I think this opinion has a solid basis in reality ;)
It's a mistake to ignore the customer Posted Dec 6, 2012 16:10 UTC (Thu) by renox (subscriber, #23785) [Link]
> The only advantage of it I can think of is familiarity; in all other respects it's inferior to prefix and suffix notations.
I agree but familiarity is very important.
Nimrod ( http://nimrod-code.org ) is a bit like this: it has no postfix operators, only prefix and infix.
It's a mistake to ignore the customer Posted Dec 6, 2012 16:28 UTC (Thu) by david.a.wheeler (guest, #72896) [Link] The only advantage of (infix) I can think of is familiarity Yes, the only advantage of infix is that nearly all educated people spend 10 to 18 years in school using infix for all arithmetic work. People who do more math-related things (e.g., programming) tend to have even more experience using infix notations than the average person. Practically all math texts (where you might get useful algorithms) use infix, too. If people spent 10 to 18 years in school exclusively using prefix or postfix instead of infix, and nearly all books used prefix or postfix, they would prefer prefix or postfix instead. But this is not reality. Are you going to change all schools and math books, worldwide, to use infix? No? Infix is not going away. And most humans do prefer the familiar. A programming language is not just for the computer, it's also for the humans. Humans can learn to use prefix, but most humans prefer to use a notation similar to what they've used for 10 or more years. The Fortran developers figured out how to do infix years ago, it's time for Lisp implementations to catch up to the first version of Fortran :-).
It's a mistake to ignore the customer Posted Dec 6, 2012 21:50 UTC (Thu) by dakas (guest, #88146) [Link] Yes, the only advantage of infix is that nearly all educated people spend 10 to 18 years in school using infix for all arithmetic work. People who do more math-related things (e.g., programming) tend to have even more experience using infix notations than the average person. Practically all math texts (where you might get useful algorithms) use infix, too. If people spent 10 to 18 years in school exclusively using prefix or postfix instead of infix, and nearly all books used prefix or postfix, they would prefer prefix or postfix instead. But this is not reality.The reality is that the most popular calculators for engineers have been HP for decades, postfix. According to your rationale, that should have been impossible. Have HP ignored their customers?
It's a mistake to ignore the customer Posted Dec 7, 2012 5:43 UTC (Fri) by bronson (subscriber, #4806) [Link]
You clearly haven't seen calculator sales this decade or last. TI and Casio have absolutely crushed HP. Both are infix. Coincidence? (maybe, who knows...?)
Don't get me wrong, my HP 48 and RPN rocketed me through 4 years of EE. But most of the other pre-Es in my classes used TI-8x and Casio FX-xxx, I assume partly because they didn't require a tutorial to do the simplest things.
So, be careful rolling out the "most popular among X" argument. Not surprisingly, that almost always supports the infix crowd.
HP calculators Posted Dec 7, 2012 15:05 UTC (Fri) by david.a.wheeler (guest, #72896) [Link]
I have an HP calculator that uses RPN. I love it.
However, almost no one else I know of can even USE it, nor are they interested in learning how. If I offered the calculator to them, they'd say no thank you, and get a calculator that supports infix instead. Most people will immediately reject something that doesn't support infix today.
It's time to support modern expectations.
It's a mistake to ignore the customer Posted Dec 6, 2012 17:18 UTC (Thu) by etienne (subscriber, #25256) [Link]
> The only advantage of [infix] I can think of is familiarity
Just to add that the main disadvantage of infix is that you have to introduce operator precedence - and having "*" priority higher than "-" but only when "*" is used as multiply (and not content-of) and only when "-" is the substraction operator (and not a negative number).
It's a mistake to ignore the customer Posted Dec 6, 2012 18:27 UTC (Thu) by vonbrand (subscriber, #4458) [Link] "Precedence" is a red herring: The precedence of +-*/ is fixed, you can easily place "all others" in one (or two) categories). Yes, C went overboard with its 13 levels; APL went overboard the other way (all operators left associative with the same precedence). Come on, parsing infix (precedence and all) is ridiculously easy. A nice, top-down parser for C is described in Fraser and Hanson's book on LCC.
It's a mistake to ignore the customer Posted Dec 7, 2012 7:23 UTC (Fri) by mathstuf (subscriber, #69389) [Link]
I like Haskell's solution: custom defined operators with 10 available precedence levels (I forget exactly, but I remember 10) with the "standard" ones spaced out along it.
It's a mistake to ignore the customer Posted Dec 7, 2012 9:39 UTC (Fri) by ekj (guest, #1524) [Link]
Isn't that terribly hard to read ?
How do you know what will happen with:
a + b [custom] c * d
Means:
(a+b) [custom] (c * d)
Or:
((a+b) [custom] c) * d
Or:
a + (b [custom] c) * d
It's a mistake to ignore the customer Posted Dec 7, 2012 16:18 UTC (Fri) by mathstuf (subscriber, #69389) [Link]
Generally, the operators don't work just on numbers and so they don't mix much with the common ones much. Its to establish order within a class of operators (e.g., within the monad operators, arrow operators, and so on). If mathematical expressions tend to get passed in to them, make them lower precedence, otherwise you can play with the higher ones.
It's a mistake to ignore the customer Posted Dec 7, 2012 10:12 UTC (Fri) by etienne (subscriber, #25256) [Link]
> Come on, parsing infix (precedence and all) is ridiculously easy.
It is not the parsing which is a problem, it is the description of functions.
I do not see how you can define a single and simple function type when you use infix, so that in a complex class tree you can derive a class and replace a random function with a simple "addition" or "greater_than". Maybe define a priority for each and every functions? Can this priority change at run-time? at instantiation time?
Note that I am using infix for my programming, so I deal with it...
It's a mistake to ignore the customer Posted Dec 6, 2012 20:37 UTC (Thu) by neilbrown (subscriber, #359) [Link]
> Just to add that the main disadvantage of infix is that you have to introduce operator precedence
I was thinking exactly the reverse - a significant *advantage* of infix is that it allows the use of precedence to reduce bracket-noise.
Some care is needed in choose the precedence levels of course but it isn't hard if you apply care.
I really do not want to try to write (let along read)
if a + 2 < b*3+1 and c & 4 == 4
in anything but precedence-aware infix notation.
It's a mistake to ignore the customer Posted Dec 6, 2012 22:08 UTC (Thu) by dakas (guest, #88146) [Link] I really do not want to try to write (let along read)Thanks for proving how problematic infix can be. That example does not look like you are aware that == has higher precedence than &. So you are arguing for something beyond your capabilities. How would it look in Scheme as presumably intended?if a + 2 < b*3+1 and c & 4 == 4in anything but precedence-aware infix notation.
(if (and (< (+ a 2)
(+ (* b 3) 1))
(= (logand c 4) 4))
...)
It's a mistake to ignore the customer Posted Dec 6, 2012 22:22 UTC (Thu) by Cyberax (✭ supporter ✭, #52523) [Link]
Thanks for pointing out stupidity of prefix syntax with your wonderful example of a one-liner turning into 5-liner.
It's a mistake to ignore the customer Posted Dec 6, 2012 22:48 UTC (Thu) by dakas (guest, #88146) [Link]
It is a 4-liner, and the material corresponding to the one-liner takes 3 lines. If mathematicians preferred minimal line count above readable grouping, why would they use fractions rather than in-line divisions?
It's a mistake to ignore the customer Posted Dec 6, 2012 23:09 UTC (Thu) by Cyberax (✭ supporter ✭, #52523) [Link]
Because paper is a bit different medium and by using vertical layout it's possible to present information more efficiently?
It's a mistake to ignore the customer Posted Dec 6, 2012 23:54 UTC (Thu) by nybble41 (subscriber, #55106) [Link]
> (if (and (< (+ a 2) (+ (* b 3) 1)) (= (logand c 4) 4)) ...)
> if (a + 2 < b * 3 + 1 && (c & 4) == 4) {...}
At 56 characters, not counting the ellipsis, the Scheme example fits easily into one line. Personally, I would probably have split it across two lines in either language, but to each his own. Granted, the corrected C version is only 42 characters, but that is offset by the need to remember the precedence of each operator, and you just demonstrated how difficult that can be. The fully parenthesized C version
> if (((a + 2) < ((b * 3) + 1)) && ((c & 4) == 4)) {...}
is 52 characters, which isn't much shorter (or more readable) than the Scheme code.
It's a mistake to ignore the customer Posted Dec 7, 2012 0:08 UTC (Fri) by Cyberax (✭ supporter ✭, #52523) [Link]
Nobody writes 2*3+1 as (2*3)+1 - everybody remembers THAT precedence rule.
So we realistically have: "if ((a+2 < b*3+1) && ((c&4) == 4)))" or 27 non-whitespace symbols. That's more compact and easier to understand.
And most people remember precedence rules of logical operators, so we have: "if (a+2 < b*3+1 && (c&4) == 4)" or 23 symbols.
Also, infix order has nice feature - it allows me to group relevant operations with whitespaces, with little "graphical" overhead.
It's a mistake to ignore the customer Posted Dec 8, 2012 9:57 UTC (Sat) by nix (subscriber, #2304) [Link] everybody remembers THAT precedence ruleI have fixed multiple bugs over the years caused by people thinking that + had higher precedence than *, or that C was strict left- or even right-associative. Yes, anyone with half a clue knows otherwise: but not every developer, alas, has half a clue to spare.
It's a mistake to ignore the customer Posted Dec 8, 2012 13:51 UTC (Sat) by paulj (subscriber, #341) [Link]
Also, clue level can vary significantly, even with a fixed, given programmer. E.g. regular diurnal patterns (pre-coffee, post-lunch, pre-knocking-off-time), when extremely tired at the end of a too-long hacking session, or even programming while drunk. :)
It's a mistake to ignore the customer Posted Dec 12, 2012 13:45 UTC (Wed) by HelloWorld (guest, #56129) [Link]
The solution to that isn't dumbing down the language but firing people who don't have half a clue.
It's a mistake to ignore the customer Posted Dec 13, 2012 11:39 UTC (Thu) by dakas (guest, #88146) [Link] The solution to that isn't dumbing down the language but firing people who don't have half a clue.Scheme is the ultimately dumbed-down language for the computer, to the degree that it does not require a parser for interpreting, just an expression reader and an evaluator. It is similarly dumbed-down to the human reader as commerce/Pidgin English is, meaning that it takes practice and control to consistently dumb down in the right manner. The purpose is having a common language for talking about programs shared between human and computer. Using infix in Scheme is like Yodish Pidgin English. Sort of defeats the original purpose of human and computer sharing a language for talking about code rather than humans expressing themselves to one another.
It's a mistake to ignore the customer Posted Dec 13, 2012 11:55 UTC (Thu) by mpr22 (subscriber, #60784) [Link] What a wonderful instance of "Humans can do the work, so machines have time to think."
It's a mistake to ignore the customer Posted Dec 13, 2012 17:26 UTC (Thu) by HelloWorld (guest, #56129) [Link]
> Scheme is the ultimately dumbed-down language for the computer,
No, it's not. As you were told multiple times by now, Scheme already has syntactic sugar for multiple constructs. 'x is (quote x), and (quote x) is (quote . (x . ())).
> Using infix in Scheme is like Yodish Pidgin English. Sort of defeats the original purpose of human and computer sharing a language for talking about code rather than humans expressing themselves to one another.
It's a mistake to ignore the customer Posted Dec 13, 2012 18:38 UTC (Thu) by viro (subscriber, #7872) [Link]
Not quite. The problem, in a sense, is that the structure chosen for representing program makes sense for optimizing interpreter a bit, at the cost of being very unnatural. Subtrees are not subexpressions. Sure, that way you avoid digging in to find the node where you'll be doing reduction, but that doesn't come for free. As the matter of fact (and you damn well know that, seeing that you seem to be familiar with e.g. Haskell), the things can be done the other way round - with APPLY being the fundamental primitive and CONS expressed via it. The same "easily represent program in the language's primary data structure" thing holds for a lot more than just LISP, e.g. when the primary data structure *is* partially evaluated expression. That's not what makes LISP LISP; neither is the syntax, of course.
It's a mistake to ignore the customer Posted Dec 7, 2012 0:22 UTC (Fri) by neilbrown (subscriber, #359) [Link]
> That example does not look like you are aware that == has higher precedence than &.
Sorry, but what language did you think I was using? Given that I used "and" and did not include () around the condition of the 'if', it certainly wasn't C. (It is missing a ':' at the end - sorry about that).
Much as I like C, it clearly got some precedence issues wrong. More modern languages do a much better job.
It's a mistake to ignore the customer Posted Dec 7, 2012 7:21 UTC (Fri) by mathstuf (subscriber, #69389) [Link]
To be fair, there is a define for 'and' to '&&' in commonly included C headers (I forget which exactly). And since there's LISP floating around, parentheses sort of fade into the background after enough programming in it, so the error(s) made aren't completely obvious. The colon probably would have helped :) .
C alternative tokens Posted Dec 7, 2012 16:42 UTC (Fri) by dtlin (✭ supporter ✭, #36537) [Link] #include <iso646.h>defines macros for C. They're in C++ by default.
Precedence Posted Dec 7, 2012 17:16 UTC (Fri) by david.a.wheeler (guest, #72896) [Link] Poster said: Just to add that the main disadvantage of infix is that you have to introduce operator precedence No you don't. Infix means the operator is between the operands, that's all. Precedence can a lot of create problems, and the SRFI-105 has a very simple solution: No built-in precedence. You can still have precedence, though. If you use multiple operations that require precedence, the whole expression is changed to "($nfx$ ...)". You can then define "$nfx$" to do whatever you want. SRFI-105 contains a detailed rationale about its approach to precedence. In practice, {3 - {4 * 5}} isn't hard to read at all, and sure beats (- 3 (* 4 5)).
It's a mistake to ignore the customer Posted Dec 6, 2012 18:33 UTC (Thu) by dlang (✭ supporter ✭, #313) [Link]
> What I don't understand is why infix is so important. The only advantage of it I can think of is familiarity
this attitude (that familiarity doesn't matter) is a major problem infecting current Linux userspace development. Gnome, Systemd, Unity, Wayland, (KDE4 to a much lesser degree) are all doing things that assume that familiarity with the existing stuff doesn't matter and that anyone who objects is just a stick-in-the-mud who needs to get with the times.
It's hard to overstate the value of familiarity. Even if the existing tools are inefficient, if they are familiar to people, it can be really bad to change them.
outside of software, one common example is the DORVAK vs QWERTY keyboard debate. Some people argue that DORVAK is significantly better (I'm not one of them by the way), but QWERTY remains dominant, even in things like phone on-screen keyboards, for the simple reason that it's familiar to people.
It's a mistake to ignore the customer Posted Dec 7, 2012 17:48 UTC (Fri) by sorpigal (subscriber, #36106) [Link]
Familiarity is a huge advantage that ought to outweigh almost anything. If, in the end, you have to spend a lot of time to understand how to write what you want, more time to read what you have written and even more time to read what someone else wrote, then you have consumed enormous amounts of time that could have been spent doing the actual work of telling the computer what to do. The time and attention of a developer is the single most valuable resource when developing just about any software today. Anything which decreases the amount of time it takes to understand a piece of code (whether writing or reading) increases productivity, all else being equal. It adds up.
maybe not only familiarity Posted Dec 7, 2012 20:57 UTC (Fri) by tpo (subscriber, #25713) [Link]
People in support of infix in this thread are using "familiarity" as an argument whereas critics are arguing that infix is *one* aspect of the Scheme language that you have to familiarise yourself with.
I'd like to propose that infix (maybe as well as prefix) as a way of thinking and understanding may be rooted in the human brain itself.
I've just read the "DCI manifesto" on Artima, where the authors are arguing that humans are understanding in terms of things and behaviors. Consequently they propose to model "things" and "behaviors" separately.
As a functional language Scheme would be on the outmost "behavior" side of the possible spectrum. Under the above stated theory it would be a compliment to the human brain that it *is* able to manipulate a symbolic problem representation that is very much focused on only one side of "things and behaviors". On the other hand it would hint to why prefix notation is hard to handle for humans - it supposedly simply doesn't match the "natural" way a brain works.
I'm completely ignorant about that topic and respective research and as such could be completely wrong, however I think we should not stop our thinking at the relatively trivial "familiarity" argument but ask whether the problem could be rooted deeper than that.
[1] "The DCI Architecture: A New Vision of Object-Oriented Programming"
maybe not only familiarity Posted Dec 10, 2012 8:38 UTC (Mon) by jezuch (subscriber, #52988) [Link]
> On the other hand it would hint to why prefix notation is hard to handle for humans - it supposedly simply doesn't match the "natural" way a brain works.
At best it's hard to handle for speakers of SVO languages. It's like arguing that Arabic (a VSO language, equivalent to prefix notation) or Japanese (a SOV language, equivalent to suffix notation) are "hard to handle" and "don't match the natural way a brain works". Try telling that to the Arabs and Japanese ;)
maybe not only familiarity Posted Dec 10, 2012 9:24 UTC (Mon) by tpo (subscriber, #25713) [Link]
I'm not familiar with VSO languages: do they also, as Scheme does, put *all* verbs at the start of the sentence in case of nested statements? As in:
(do (another_do (yet_another_do (and_more_do (and_still_more_do arg arg
aka
verb1 verb2 verb3 verb4 verb5 subject1 object 1 subject2 object2 object2a
I honestly do not know, but I'd guess even a VSO language will not work that way as opposed to Lisp'ish languages?
maybe not only familiarity Posted Dec 10, 2012 17:06 UTC (Mon) by nybble41 (subscriber, #55106) [Link] Deeply nested expressions are a problem in any language, moreso in natural languages which are not traditionally formatted to highlight the subexpressions. If you find yourself writing such expressions in Scheme, you may want to look into refactoring the code, or at least taking advantage of the "nest" macro to flatten the expression. An example: (do arg1
(another_do
(yet_another_do
(and_more_do arg2
(and_still_more_do arg3 arg4)))))
is equivalent to: (nest [(do arg1)
(another-do)
(yet-another-do)
(and-more-do arg2)
(and-still-more-do arg3)]
arg4)
Curly-infix and readable Lisp Posted Dec 4, 2012 21:10 UTC (Tue) by HelloWorld (guest, #56129) [Link] and if you get the latter, it will be hard to figure the "flipping point" where #{ } will get used over normal list syntax in output, and where not.The sweeten tool does this already. It employs heuristics to decide questions like these. They aren't perfect, but what's the worst that could happen? You get a string representation of a data structure that isn't as nice as it could have been, so what? And frankly, things like (second '#{ 3 + 4 #}) => 3 and (cddr '#{ 3 + 4 + 5 #}) => (4 5) will not particularly facilitate understanding.Then don't write it that way. Besides, it's no more confusing than (car ''x) => quote
But conversion to infix is a different beast than converting a conventional arrangement of dotted pairs to list syntax.I don't see why.
Curly-infix and readable Lisp Posted Dec 5, 2012 8:26 UTC (Wed) by dakas (guest, #88146) [Link] The sweeten tool does this already. It employs heuristics to decide questions like these.Meaning that the output is not predictable and can change from version to version. They aren't perfect, but what's the worst that could happen? You get a string representation of a data structure that isn't as nice as it could have been, so what?You need to be fluid in two languages instead of just one and transparently deal with either output. The whole point of infix notation is to reduce the amount of thinking you need to invest. Now you need to be fluid in two representations and transparently translate back if sweeten decided to "infixify" a list that was not intended as an arithmetic expression, and vice versa. At any rate, I am just making predictions. The only one in a position to dispel them is Father Time. I suspect I have had him visiting more often than you did, but at any rate I'm willing to take what he will eventually have to say in that matter.
Curly-infix and readable Lisp Posted Dec 5, 2012 21:10 UTC (Wed) by david.a.wheeler (guest, #72896) [Link] dakas said: Meaning that the output is not predictable and can change from version to version. You have the incorrect belief that that Scheme output is currently predictable and cannot change from version to version. That is not true, of either the Scheme spec or its implementations. The Scheme specification R7RS draft 7 for "write" is "Writes a representation of obj to the given textual output port". Note that this is *a* representation, not *the* representation, as there are many possible representations without curly-infix. Similar text exists for R6RS (library section 8.2.12 on put-datum), and R5RS (section 6.6.3); it always says "a" not "the" and does not proscribe a particular representation. Different Scheme implementations do write the same list differently, too. Let's run the trivial program (write (read)) and give the program the input ''x (x quoted twice). The scsh version 0.6.7 implementation reports ''x, while guile version 1.8.7 reports (quote (quote x)) - obviously different from scsh. Since Scheme does not guarantee a particular format for a list - and permits implementations to use abbreviations when they choose - curly-infix represents no change in this matter. The "sweeten" heuristic is to write infix form if there are 3-6 parameters, and the operator is punctuation, "and", or "or". It's a longer heuristic, but it means that users can see {a > b} instead of (> a b), and a lot of users prefer the latter.
You need to be fluid in two languages instead of just one and transparently deal with either output. There is no "two languages". There is an underlying list notation, and a simple abbreviation that you can optionally use. Yes, you have to fluid in the two representations. Give it 10 minutes, you'll get it. At any rate, I am just making predictions. The only one in a position to dispel them is Father Time. I suspect I have had him visiting more often than you did, but at any rate I'm willing to take what he will eventually have to say in that matter. Here we agree!
(Typo fix) Posted Dec 5, 2012 21:20 UTC (Wed) by david.a.wheeler (guest, #72896) [Link]
s/a lot of users prefer the latter/a lot of users prefer infix/
Curly-infix and readable Lisp Posted Dec 6, 2012 20:12 UTC (Thu) by vonbrand (subscriber, #4458) [Link] In my experience, each time you try to please everyone, you end up with an angry mob.
Curly-infix and readable Lisp Posted Dec 6, 2012 22:11 UTC (Thu) by dakas (guest, #88146) [Link]
Which is probably saying more about humanity than Scheme, but so true.
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