9 ms·

Reading some of the replies that interpret pg's essay as talking about "libraries" or "frameworks" or "metaprogramming" doesn't look quite right to me. I argue

by jasode 9y ago

Reading some of the replies that interpret pg's essay as talking about "libraries" or "frameworks" or "metaprogramming" doesn't look quite right to me. I argue that instead of those 3, the most applicable terminology to map to pg's idea would be a "DSL" ("Domain Specific Language".)[1] The "DSL" terminology seemed to have gained currency around 2008 so this old 1993 essay wasn't able to use it. In any case, his point is to program Lisp in such a way as to build a "DSL" inside of Lisp and you then program your higher level concepts on that DSL. His key quotes: >a principle which could be called bottom-up design-- changing the language to suit the problem. In Lisp, you don't just write your program down toward the language, you also build the language up toward your program. >Instead of a single, monolithic program, you will get a larger language with more abstract operators, and a smaller program written in it. One can also pursue the "DSL" concept with other programming languages. In C++, you can design the classes to be a "DSL". In fact, one of the derided features of C++ such as operator-overloading was motivated by allowing a custom "DSL" to integrate into the language better. Lisp is an interesting programming language for writing an embedded DSL because the custom "mini language" you write looks like other builtin Lisp syntax. Why the other proposed terms don't seem to fit: - "metaprogramming" : this is usually describing programs generating other programs either at compile time (e.g. templates) or runtime (e.g. the eval() function in Javascript/Python) - "libraries" : these are often non-domain-specific reusable code... such as a string library, matrix math library, or a TCPIP library - "framework" : this is usually a source-code runtime (basically an application "loop") with customization points to call your custom code PG's essay like many other programming essays suffers from misinterpretation because it doesn't include any explicit source code to illustrate the ideas. Therefore, writing in metaphors invites misunderstanding. [1] https://en.wikipedia.org/wiki/Domain-specific_language https://en.wikipedia.org/wiki/Domain-specific_language

lispm 9y ago
> currency around 2008 so this old 1993 essay wasn't able to use it Embedding languages in Lisp is a concept since around 1962 (Daniel Bobrows METEOR Lisp extension for pattern based string processing). There are a bunch of Lisp articles written before 1980 which describe it and advocate using it. > Lisp is an interesting programming language for writing an embedded DSL because the custom "mini language" you write looks like other builtin Lisp syntax. Not really. Lisp is useful for DSL development because it provides the necessary extension features: which allows one to reuse a lot of the Lisp machinery (reader/parser, interpreter, compiler, macros, object-system, memory management, ...). Common Lisp already comes with DSLs as part of the standard: format strings and LOOP are examples. They actually don't look like Lisp syntax - format strings are radically different and LOOP statements use more algol like syntax. example for a FORMAT string: CL-USER 2 > (format t "~{~#[~;~a~;~a and ~a~:;~@{~a~#[~;, and ~:;, ~]~}~]~}" (list 1 2 3 4 5)) 1, 2, 3, 4, and 5 NIL example for a LOOP form: CL-USER 3 > (loop for i in '(1 324 2345 323 2 4 235 252) when (oddp i) do (print i) and collect i into odd-numbers and do (terpri) else collect i into even-numbers finally (return (values odd-numbers even-numbers))) 1 2345 323 235 (1 2345 323 235) (324 2 4 252) > "metaprogramming" : this is usually describing programs generating other programs either at compile time metaprogramming means to be able to program on the language level. It has not much to do with program generation. For example in Lisp you can program new syntactic constructs via macros. One can also program the 'reader' which allows one to program the token reader. There are various other ways to program at the language level - the most complex is the Meta-Object Protocol of CLOS, the Common Lisp Object System - which allows one to program the object system system itself in itself. metaprogramming facilities are tools to develop DSLs.
- jasode 9y ago
  >Embedding languages in Lisp is a concept since around 1962 You misunderstood what I wrote. I was talking about the terminology PG used, not the concept. PG couldn't time-travel to the future and write "DSL" in his 1993 essay so more readers would instantly understand what he was talking about. > it provides the necessary extension features: which allows one to reuse a lot of the Lisp machinery I agree. The "looks built in" is a characterization that some Lisp programmers (maybe not you) would call the ability to add "new syntax" to Lisp. It's a way of contrasting with something like C++. You can't "extend the C++ language" with new syntax for your custom project unless you fork the GCC or Clang compiler and add new keywords to the parser. All new so-called capabilities to embed a "DSL" has to be done as "functions()" with obvious parentheses to call it. Lisp ("code is data!") doesn't have this hard boundary. >metaprogramming means to be able to program on the language level. I agree. There's parsing/manipulating its own AST as a data structure but "metaprogramming" also has lot of currency usage to describe programs writing programs and the usage of dynamic eval().
  - lispm 9y ago
    > I was talking about the terminology PG used What now is called 'embedded domain specific language' was called 'embedded language' in Lisp. The name is slightly shorter, but the concept is/was the same.
    - jasode 9y ago
      >What now is called 'embedded domain specific language' was called 'embedded language' in Lisp. Exactly! If you do "Ctrl+F" search on PG's essay, you'll see it does _not_ have the phrase "embedded language" nor "embedded domain specific language". What exactly are you nitpicking?
      - lispm 9y ago
        That he could have used the term 'embedded language', which was used in Lisp decades before he wrote his article. So the article is probably not about embedded DSLs. What he describes is actually extending the language to express the domain - but that does still not mean that the language is 'specific'. It's not necessarily even an embedded language.
astrobe_ 9y ago
The whole point of Forth was that you didn't write programs in Forth you wrote vocabularies in Forth. When you devised an application you wrote a hundred words or so that discussed the application and you used those hundred words to write a one line definition to solve the application. It is not easy to find those hundred words, but they exist, they always exist. -- Chuck Moore, 1x Forth (1999)
montrose 9y ago
It is from the introduction to On Lisp, and there is a great deal of explicit source code in that. A lot of which is in fact about domain-specific languages. http://paulgraham.com/onlisptext.html http://paulgraham.com/onlisptext.html

by jasode 9y ago

lispm 9y ago

> currency around 2008 so this old 1993 essay wasn't able to use it Embedding languages in Lisp is a concept since around 1962 (Daniel Bobrows METEOR Lisp extension for pattern based string processing). There are a bunch of Lisp articles written before 1980 which describe it and advocate using it. > Lisp is an interesting programming language for writing an embedded DSL because the custom "mini language" you write looks like other builtin Lisp syntax. Not really. Lisp is useful for DSL development because it provides the necessary extension features: which allows one to reuse a lot of the Lisp machinery (reader/parser, interpreter, compiler, macros, object-system, memory management, ...). Common Lisp already comes with DSLs as part of the standard: format strings and LOOP are examples. They actually don't look like Lisp syntax - format strings are radically different and LOOP statements use more algol like syntax. example for a FORMAT string: CL-USER 2 > (format t "~{~#[~;~a~;~a and ~a~:;~@{~a~#[~;, and ~:;, ~]~}~]~}" (list 1 2 3 4 5)) 1, 2, 3, 4, and 5 NIL example for a LOOP form: CL-USER 3 > (loop for i in '(1 324 2345 323 2 4 235 252) when (oddp i) do (print i) and collect i into odd-numbers and do (terpri) else collect i into even-numbers finally (return (values odd-numbers even-numbers))) 1 2345 323 235 (1 2345 323 235) (324 2 4 252) > "metaprogramming" : this is usually describing programs generating other programs either at compile time metaprogramming means to be able to program on the language level. It has not much to do with program generation. For example in Lisp you can program new syntactic constructs via macros. One can also program the 'reader' which allows one to program the token reader. There are various other ways to program at the language level - the most complex is the Meta-Object Protocol of CLOS, the Common Lisp Object System - which allows one to program the object system system itself in itself. metaprogramming facilities are tools to develop DSLs.

jasode 9y ago
>Embedding languages in Lisp is a concept since around 1962 You misunderstood what I wrote. I was talking about the terminology PG used, not the concept. PG couldn't time-travel to the future and write "DSL" in his 1993 essay so more readers would instantly understand what he was talking about. > it provides the necessary extension features: which allows one to reuse a lot of the Lisp machinery I agree. The "looks built in" is a characterization that some Lisp programmers (maybe not you) would call the ability to add "new syntax" to Lisp. It's a way of contrasting with something like C++. You can't "extend the C++ language" with new syntax for your custom project unless you fork the GCC or Clang compiler and add new keywords to the parser. All new so-called capabilities to embed a "DSL" has to be done as "functions()" with obvious parentheses to call it. Lisp ("code is data!") doesn't have this hard boundary. >metaprogramming means to be able to program on the language level. I agree. There's parsing/manipulating its own AST as a data structure but "metaprogramming" also has lot of currency usage to describe programs writing programs and the usage of dynamic eval().
- lispm 9y ago
  > I was talking about the terminology PG used What now is called 'embedded domain specific language' was called 'embedded language' in Lisp. The name is slightly shorter, but the concept is/was the same.
  - jasode 9y ago
    >What now is called 'embedded domain specific language' was called 'embedded language' in Lisp. Exactly! If you do "Ctrl+F" search on PG's essay, you'll see it does _not_ have the phrase "embedded language" nor "embedded domain specific language". What exactly are you nitpicking?
    - lispm 9y ago
      That he could have used the term 'embedded language', which was used in Lisp decades before he wrote his article. So the article is probably not about embedded DSLs. What he describes is actually extending the language to express the domain - but that does still not mean that the language is 'specific'. It's not necessarily even an embedded language.

astrobe_ 9y ago

The whole point of Forth was that you didn't write programs in Forth you wrote vocabularies in Forth. When you devised an application you wrote a hundred words or so that discussed the application and you used those hundred words to write a one line definition to solve the application. It is not easy to find those hundred words, but they exist, they always exist. -- Chuck Moore, 1x Forth (1999)

montrose 9y ago

It is from the introduction to On Lisp, and there is a great deal of explicit source code in that. A lot of which is in fact about domain-specific languages. http://paulgraham.com/onlisptext.html http://paulgraham.com/onlisptext.html