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(Shameless self-promotion) I just finished by thesis on a new programming language called SolScript, which is reactive and based on "math". It's a hard real-ti

(Shameless self-promotion) I just finished by thesis on a new programming language called SolScript, which is reactive and based on "math". It's a hard real-time language for avionics software, BUT it has type inference and duck typing (everything is "symbolic"). SolScript is supposed to look familiar to anyone with a basic knowledge of mathematics. It's also a literate language, because every SolScript file is a Markdown file (and SolScript code is inside Markdown code blocks). [link redacted]

lomnakkus 12y ago
Just had a little glance (I'm on my way out the door), but if it's possible to construct arbitrarily large lists (as seems to be implied by the availability of e.g. "range N" for any N, how can you guarantee that e.g. "sum large_list" can actually terminate within the time bound set by the frequency? Also there seems to be no actual proof of safety of the language's semantics (are the semantics formally specified?), but perhaps I missed it.
- AlexanderDhoore 12y ago
  The length of all lists is known at compile-time. So, yes, you can do "sum range hugeNumber", but the compiler will tell you that your program can't be run at the correct frequency. (The possible range of the `hugeNumber` variable is known to the compiler, so it can know the maximum size of the list you are asking.) The compiler can find out the range of numbers and the lengths of lists using static analysis, because SolScript is such a "restricted" language. Functional programmers would probably dump all that information into a type system. We call it "dataflow analysis", but I think the end result is the same. Note that, all of the static analysis is done on the dataflow graph underlying a SolScript program. In the dataflow graph there are no "functions" or "classes"... The static analysis is much simpler because it is done on something more primitive than the language itself.
DavidSJ 12y ago
Very interesting work. Is there a development list or some other way to follow progress?
- AlexanderDhoore 12y ago
  Well, there is the main company website[1], but that's more for "marketing" purposes. In the future, there will be a website dedicated to SolScript itself. This website will be the "technical" website. We already have a domain [2], but there's no website there. Right now, we are working on getting SolScript into production. This thesis was really the first time anyone ever wrote anything about SolScript. Part of my job, in the future, will be to write blog posts and create tutorials. I'll definitely keep HN posted! [1] http://www.unmanned.aero/ http://www.unmanned.aero/ [2] http://solscri.pt/ http://solscri.pt/
  - mietek 12y ago
    This looks really cool. Congratulations on the launch. BTW, there's a broken link on your home page: /71of71 instead of /71objectives
jacquesm 12y ago
- real time - avionics - type inference - duck typing You like challenges don't you? ;) I like the literate component a lot, I can see why that would be a very big plus when you're building avionics software. Bookmarked your thesis. What was your reason for going for 'duck typed' and 'scripted' rather than strongly typed and compiled? (Which I would assume to be a whole lot more suited for the intended branch of industry, so that has me curious.) At the surface of it this looks like a 'textual spreadsheet' with the lines replacing the cells of the sheet. This 'spreadsheet' is then evaluated 'x' times per second to satisfy the hard real time requirements. How do you stabilize the results from one 'tick' to the next? Do you keep a shadow copy that you work on with all the results posted to the next generation? There is something funny about a person working for a small software outfit choosing a format for textfiles (for really good reasons) because Microsoft or Apple might not be around when the files need to be read. I get your reasoning and agree with it completely but you have to balance that against the chances of your own company not being around anymore either. How much of the software of the original Boeing 747 is still in use today? I'd imagine there are no fuselages that have not been upgraded multiple times since the first 747's took flight. So the lifespan of the documentation is roughly the same as the lifespan of the software. Are there any public sources out there? Here are some of the oldest 747 airframes known to be still on active duty: http://www.airliners.net/aviation-forums/general_aviation/read.main/2863915/ http://www.airliners.net/aviation-forums/general_aviation/re... But that does not say much about the avionics in them. Do you intend to release the source to solscript in order to profit from the 'many eyes' out there to reduce the number of bugs in the runtime? (Which can't be written in solscript, so effectively will have to be written in some unsafe language.) I like that markdown trick a lot, that's applicable to just about every programming environment, see: http://michael-sokol.tumblr.com/post/13112309135/literate-programming-with-github-and-markdown http://michael-sokol.tumblr.com/post/13112309135/literate-pr...
- AlexanderDhoore 12y ago
  Haha, that's a lot of questions. Let me try to go over them. I say SolScript is "duck typed" and "scripted", because that's how it feels to program SolScript. However, under the hood, SolScript is a statically typed, compiled language. About the "spreadsheet" idea, that is exactly what the SolScript IDE (Solide) is going to be. There will be a spreadsheet mode, which displays the source code as a spreadsheet. The last chapter talks about Solide, if you want to know more. (The creation of Solide is going to be my job, and I've been watching Bret Victor videos, all day yesterday, for inspiration.) We have no "deep copy" of the data. The data is simply mutated in place, for performance. The compiler knows in what order it has to update the datacells, so SolScript users don't notice any of this. If I say `b = a`, then `a` will be calculated before `b` uses it. (If you want the value of `a` before `a` is updated, you say `b = previous a`.) The whole "plain text" argument is about the fact that companies can die. So can (UN)MANNED, of course. The difference is that plain text files will always be readable, in contrast to Word files. You don't need our software to read plain text documentation. Releasing the source is not something we plan to do (for now). We are not against the idea, but right now we have other priorities. There will probably be a gratis version, even for commercial use. Only that version won't be certified. Yes, SolScript is written in an "unsafe" language: C. This makes it extremely cross-platform. We can run on Linux, OS X, Windows, iOS, VxWorks... The coding standards of our C code are extremely strict. Avionics style. And about Markdown, yes that could be applied to other programming languages. BUT SolScript integrates with Markdown on a whole new level. For example, sections in Markdown are the scopes or namespaces of a SolScript program. Markdown is built into SolScript, not tacked on. Edit: Circular dependencies really make no sense, in a declarative programming language. Defining `a = b` and `b = a` has no clear meaning, so the compiler will throw an error. However, you can define things recursively using `previous`. For example: `a = b + 1 initially 0` and `b = previous a`. In this case, `b` is 0, 1, 2, 3... and `a` is 1, 2, 3, 4...
vanderZwan 12y ago
Any reason why the thesis itself isn't presented a complete and valid SolScript program? ;)

lomnakkus 12y ago

Just had a little glance (I'm on my way out the door), but if it's possible to construct arbitrarily large lists (as seems to be implied by the availability of e.g. "range N" for any N, how can you guarantee that e.g. "sum large_list" can actually terminate within the time bound set by the frequency? Also there seems to be no actual proof of safety of the language's semantics (are the semantics formally specified?), but perhaps I missed it.

AlexanderDhoore 12y ago
The length of all lists is known at compile-time. So, yes, you can do "sum range hugeNumber", but the compiler will tell you that your program can't be run at the correct frequency. (The possible range of the `hugeNumber` variable is known to the compiler, so it can know the maximum size of the list you are asking.) The compiler can find out the range of numbers and the lengths of lists using static analysis, because SolScript is such a "restricted" language. Functional programmers would probably dump all that information into a type system. We call it "dataflow analysis", but I think the end result is the same. Note that, all of the static analysis is done on the dataflow graph underlying a SolScript program. In the dataflow graph there are no "functions" or "classes"... The static analysis is much simpler because it is done on something more primitive than the language itself.

DavidSJ 12y ago

Very interesting work. Is there a development list or some other way to follow progress?

AlexanderDhoore 12y ago
Well, there is the main company website[1], but that's more for "marketing" purposes. In the future, there will be a website dedicated to SolScript itself. This website will be the "technical" website. We already have a domain [2], but there's no website there. Right now, we are working on getting SolScript into production. This thesis was really the first time anyone ever wrote anything about SolScript. Part of my job, in the future, will be to write blog posts and create tutorials. I'll definitely keep HN posted! [1] http://www.unmanned.aero/ http://www.unmanned.aero/ [2] http://solscri.pt/ http://solscri.pt/
- mietek 12y ago
  This looks really cool. Congratulations on the launch. BTW, there's a broken link on your home page: /71of71 instead of /71objectives

jacquesm 12y ago

- real time - avionics - type inference - duck typing You like challenges don't you? ;) I like the literate component a lot, I can see why that would be a very big plus when you're building avionics software. Bookmarked your thesis. What was your reason for going for 'duck typed' and 'scripted' rather than strongly typed and compiled? (Which I would assume to be a whole lot more suited for the intended branch of industry, so that has me curious.) At the surface of it this looks like a 'textual spreadsheet' with the lines replacing the cells of the sheet. This 'spreadsheet' is then evaluated 'x' times per second to satisfy the hard real time requirements. How do you stabilize the results from one 'tick' to the next? Do you keep a shadow copy that you work on with all the results posted to the next generation? There is something funny about a person working for a small software outfit choosing a format for textfiles (for really good reasons) because Microsoft or Apple might not be around when the files need to be read. I get your reasoning and agree with it completely but you have to balance that against the chances of your own company not being around anymore either. How much of the software of the original Boeing 747 is still in use today? I'd imagine there are no fuselages that have not been upgraded multiple times since the first 747's took flight. So the lifespan of the documentation is roughly the same as the lifespan of the software. Are there any public sources out there? Here are some of the oldest 747 airframes known to be still on active duty: http://www.airliners.net/aviation-forums/general_aviation/read.main/2863915/ http://www.airliners.net/aviation-forums/general_aviation/re... But that does not say much about the avionics in them. Do you intend to release the source to solscript in order to profit from the 'many eyes' out there to reduce the number of bugs in the runtime? (Which can't be written in solscript, so effectively will have to be written in some unsafe language.) I like that markdown trick a lot, that's applicable to just about every programming environment, see: http://michael-sokol.tumblr.com/post/13112309135/literate-programming-with-github-and-markdown http://michael-sokol.tumblr.com/post/13112309135/literate-pr...

AlexanderDhoore 12y ago
Haha, that's a lot of questions. Let me try to go over them. I say SolScript is "duck typed" and "scripted", because that's how it feels to program SolScript. However, under the hood, SolScript is a statically typed, compiled language. About the "spreadsheet" idea, that is exactly what the SolScript IDE (Solide) is going to be. There will be a spreadsheet mode, which displays the source code as a spreadsheet. The last chapter talks about Solide, if you want to know more. (The creation of Solide is going to be my job, and I've been watching Bret Victor videos, all day yesterday, for inspiration.) We have no "deep copy" of the data. The data is simply mutated in place, for performance. The compiler knows in what order it has to update the datacells, so SolScript users don't notice any of this. If I say `b = a`, then `a` will be calculated before `b` uses it. (If you want the value of `a` before `a` is updated, you say `b = previous a`.) The whole "plain text" argument is about the fact that companies can die. So can (UN)MANNED, of course. The difference is that plain text files will always be readable, in contrast to Word files. You don't need our software to read plain text documentation. Releasing the source is not something we plan to do (for now). We are not against the idea, but right now we have other priorities. There will probably be a gratis version, even for commercial use. Only that version won't be certified. Yes, SolScript is written in an "unsafe" language: C. This makes it extremely cross-platform. We can run on Linux, OS X, Windows, iOS, VxWorks... The coding standards of our C code are extremely strict. Avionics style. And about Markdown, yes that could be applied to other programming languages. BUT SolScript integrates with Markdown on a whole new level. For example, sections in Markdown are the scopes or namespaces of a SolScript program. Markdown is built into SolScript, not tacked on. Edit: Circular dependencies really make no sense, in a declarative programming language. Defining `a = b` and `b = a` has no clear meaning, so the compiler will throw an error. However, you can define things recursively using `previous`. For example: `a = b + 1 initially 0` and `b = previous a`. In this case, `b` is 0, 1, 2, 3... and `a` is 1, 2, 3, 4...

vanderZwan 12y ago

Any reason why the thesis itself isn't presented a complete and valid SolScript program? ;)