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0 pointskung-fu-master15y ago0 comments

I'm not a Lisp expert, so I have another question. Is it possible to embed DSL into Lisp which will looks like pseudo-code?

For example:

(pseudo

    a = 0

    b = 100

    s = 0

    for (i from a to b)

        s = s + i

    write(s)

)

If such pseudo code can be embedded into SBCL it would generate fast machine code, also it would be possible to easily modify pseudo code syntax.

0 comments

lisper15y ago

http://rondam.blogspot.com/2008/02/joy-of-iterators.html

This lets you write things like:

(for var in form do ...

(for var in form collect ...

where form can be anything that has an iterator method defined on it.

There's also a macro I use called BINDING-BLOCK (BB for short) which subsumes a bunch of binding forms. So you can write things like:

(bb

  x (...)

  y (...)

  :db (q r s) (...) ; Destructuring-bind

  :mv (p q) (...) ; Multiple-value-bind

  ...

It's extensible so you can add your own clauses. Code is here:

http://www.flownet.com/ron/lisp/rg-utils.lisp

(It's a little out of date. If you want the latest let me know and I'll update it.)

namekuseijin15y ago

that's bad assembly-style pseudo-code and thinking. Lisp favors higher-level, functional pseudo-code that readily runs as is!

like in scheme: (write (let for ((i 0) (s 0)) (if (> i 100) s (for (+ 1 i) (+ i s)))))

why would you care for those a, b, or s variables in the first place when all you want is the sum? The above expression writes the sum as computed by a recursive approach using lexical bindings.

you may of course abstract it away into a function: (define (for from to doit result) (if (> from to) result (for (+ 1 from) to doit (doit from result))))

and use it: (write (let ((a 0) (b 100)) (for a b + 0)))

I didn't even need macros yet!

lispm15y ago

sure, that's possible - just see the LOOP macro...

kung-fu-masterOP15y ago

Then, why no one still not made such eDSL? As I understand, the only reason to choose Python for Peter Norvig was the similarity of Python to pseudo-code. I think that such great hacker as Peter Norvig could easily develop pseudo-code eDSL on top of Lisp macro-system.

As school teacher on programming I'm limited in choice of programming languages. The only language which I can study is Pascal (a lot of other reasons on it). The problem is that Pascal have not any libraries (GUI, 2D/3D, Game Development Engines, programming micro-controllers, ...). Students can write only simple console applications. So, it was be ideal to have subset of Pascal as eDSL on top of Common Lisp or Clojure. In that way I can easily extend original Pascal to access some real world libraries.

I think also on top of Common Lisp we can develop some simpler eDSL as pseudo-code for beginner students.

PS: gone to learn Common Lisp...

MageSlayer15y ago

>The problem is that Pascal have not any libraries (GUI, 2D/3D, Game Development Engines, programming micro-controllers, ...).

It's not true. Lazarus (http://www.lazarus.freepascal.org/) gives pretty much everything Delphi has. Currently I develop OpenGL 2D analytical tool. Again GUI is on par with Delphi.

lispm15y ago

There are such DSLs on top of Common Lisp. But usually not on the scope of a full programming language like Pascal. It is not that typical anymore, but there are examples in that direction.

LOOP shows some of the practical problem. For example for LOOP one needs a custom highlighter in the IDE, because it has its own complex syntax, which does not follow the basic Lisp model. Same for indentation / code formatting. There maybe other problems.

There is another Iteration facility as a library for Common Lisp called ITERATE. It is very similar to LOOP, but the syntax is a bit more oriented towards Lisp.

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lisper15y ago

http://rondam.blogspot.com/2008/02/joy-of-iterators.html

This lets you write things like:

(for var in form do ...

(for var in form collect ...

where form can be anything that has an iterator method defined on it.

There's also a macro I use called BINDING-BLOCK (BB for short) which subsumes a bunch of binding forms. So you can write things like:

(bb

  x (...)

  y (...)

  :db (q r s) (...) ; Destructuring-bind

  :mv (p q) (...) ; Multiple-value-bind

  ...

It's extensible so you can add your own clauses. Code is here:

http://www.flownet.com/ron/lisp/rg-utils.lisp

(It's a little out of date. If you want the latest let me know and I'll update it.)

namekuseijin15y ago

that's bad assembly-style pseudo-code and thinking. Lisp favors higher-level, functional pseudo-code that readily runs as is!

like in scheme: (write (let for ((i 0) (s 0)) (if (> i 100) s (for (+ 1 i) (+ i s)))))

why would you care for those a, b, or s variables in the first place when all you want is the sum? The above expression writes the sum as computed by a recursive approach using lexical bindings.

you may of course abstract it away into a function: (define (for from to doit result) (if (> from to) result (for (+ 1 from) to doit (doit from result))))

and use it: (write (let ((a 0) (b 100)) (for a b + 0)))

I didn't even need macros yet!

lispm15y ago

sure, that's possible - just see the LOOP macro...

kung-fu-masterOP15y ago

I think also on top of Common Lisp we can develop some simpler eDSL as pseudo-code for beginner students.

PS: gone to learn Common Lisp...

MageSlayer15y ago

>The problem is that Pascal have not any libraries (GUI, 2D/3D, Game Development Engines, programming micro-controllers, ...).

It's not true. Lazarus (http://www.lazarus.freepascal.org/) gives pretty much everything Delphi has. Currently I develop OpenGL 2D analytical tool. Again GUI is on par with Delphi.

lispm15y ago

There are such DSLs on top of Common Lisp. But usually not on the scope of a full programming language like Pascal. It is not that typical anymore, but there are examples in that direction.

There is another Iteration facility as a library for Common Lisp called ITERATE. It is very similar to LOOP, but the syntax is a bit more oriented towards Lisp.

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