[corinroyal]

I'm always baffled by hate for DSLs until I realize that what people are criticizing aren't DSLs, but DSLs you have to write from scratch. If you host your DSL on Lisp, then all you have to write is your domain logic, not the base language. Most of the work is already done, and your language is useful from day one. I don't understand why people insist on creating new languages from scratch just to watch them die on the vine, when these langs could have been hosted DSLs on Lisp and actually get used.

[TimTheTinker]

Not just Lisp, but any language that has strong support for either literal in-language data expressions like JSON or YAML, or meta-language support like Ruby, Elixir, JSX/TSX (or both!).

Every time you write a React JSX expression, terraform file, config.yaml, etc., you're using a DSL.

I once wrote a JSON DSL in Ruby that I used for a template-based C# code generator. This enabled a .NET reporting web app to create arbitrarily shaped reports from arbitrary rdmbs tables, saving our team thousands of hours. Another team would upload report data to a SQL Server instance, write a JSON file in the DSL, check it against a tiny schema validator website, submit it, and their reports would soon be live. One of the most productive decisions I ever made.

[hot_gril]

Technically yeah, but JSX isn't what people think of when you mention a DSL. I know JS, I know HTML, so I know JSX immediately since it's just templatized HTML inside JS.

[CyberDildonics]

This is generally a terrible way to work. Making a bunch of custom syntax even in the same language is just adding more stuff to memorize for no gain.

Even in C using the "goes to operator" of while(i --> 0) or using special operator overloading like the C++ STL >> and << operators for concatenation is just making people memorize nonsense so someone writing can be clever.

People don't give presentations with riddles and limericks either. It can be clever as a puzzle but when things need to get done, it is just indulging someone showing off their cleverness at the expense of everyone who has to deal with it.

[f1shy]

I think you misunderstood what a DSL is, or at least the point of the OP?

We are advocating exactly to keep the syntax the same as the base language, and add semantic value through the abstractions of the language.

[CyberDildonics]

I didn't misunderstand anything.

If you're not changing any syntax and are just using normal function calls, that's an API and that's direct.

If you're not just using normal function calls and are making your own "semantic value through abstractions of the language" you aren't making something that is direct and are creating something that needs to be memorized.

The cleverness and indirection of the new stuff that hides what is really going on is 99% of the time not worth what it gives you, because you have to memorize this new clever thing someone came up with, then you have to learn what it is actually doing underneath that is being hidden.

[f1shy]

> If you're not changing any syntax and are just using normal function calls, that's an API and that's direct.

No. Sorry. Wrong. Look SICP where they explain the concept of embedded DSl. Hint: you may be conflating syntax and language.

[CyberDildonics]

Everyone understands the concept. Understanding why you shouldn't do it is what takes experience.

If you look at the source code for doom it is very straight forward. No fancy stuff, not cleverness, no pageantry of someone else's idea of what "good programming" is, just what needs to happen to make the program.

I'll even give you an example of an exception. Most for loops in C and successors are more complicated than they need to be. Many loops are looping from 0 to a final index and they need a variable to keep track which index they are on. Instead of a verbose for loop, you can make a macro to always loop from 0 and always give you an index variable, so you just give it the length and what symbol to use. Then you have something simplified and that's useful. It's shorter, it's clear, it will save bugs and be easier to read when you need nested loops through arrays with multiple dimensions.

I already gave examples before where clever extra syntax creates an exceptional situation but gains nothing.

The fundamental point here is that these opportunities are rare. Thinking that making up new syntax is a goal of programming is doing a disservice to everyone who has to deal with it in the future.

[f1shy]

You are 100% right in all, except you are talking about syntax extensions (the for example) and not DSL. A DSL does not need a new syntax, is a collection of abstractions that allow to express problems in the language of the domain problem. It is not an API, because is not an interface for a functionality. Is not about exposing functionality, but to add semantic value to the upper layers. May (not necessarily, but may) be formed by a collection of functions, in that case similar to an API, in that sense. Sometimes may include indeed extensions to a language, but in that case by the standard means of abstraction preferred in that language: clases, templates, functions, structures. The key is to reduce the cognitive load for the end programmers, who could be expert in the problem at hand, but not in the underlying language of the embedding.

There is also the possibility of embedding in a non programming language, like XML (E.g. launch language in ROS), or S-exp in the Oracle listener config file. Also you can do ad-hoc like in the .msg files of ROS. But is always about semantics, not syntax. Syntax is the medium only.

[vbezhenar]

If you wrote some functions, it's not DSL, it's functions.

If you calling them in a fancy way with overloads and whatnot, it's not DSL, it's fancy functions.

DSL is domain specific language. It includes domain specific syntax, domain specific semantics and domain specific libraries.

[f1shy]

Absolutely no. It may have specific syntax, but is not needed. Where do you have such definition? In fact the typical example is in Lisps, where you add no syntax.

Is not about fancy functions. And not about new syntax. Is about adding semantic value. If somebody adds a collection of functions that allow the expression of solutions to a problem in the very language of the problem, that is a DSL, if the syntax chosen, for whatever reason, e.g. simplicity, happens to be the same as some underlying language, that takes nothing to the fact that it is a DSL.

If you look at the examples of SICP, they are “just” fancy functions. But they are DSLs

An extract of the wikipedia article:

As embedded domain-specific language (eDSL)[4] also known as an internal domain-specific language, is a DSL that is implemented as a library in a "host" programming language. The embedded domain-specific language leverages the syntax, semantics and runtime environment (sequencing, conditionals, iteration, functions, etc.) and adds domain-specific primitives that allow programmers to use the "host" programming language to create programs that generate code in the "target" programming language.

[f1shy]

Exactly. Good DSL are typically (although not always) embedded in another. When that is the case, they tend to be a perfect abstraction (if decently implemented)

[PaulHoule]

with static imports in Java I buld DSLs that are basically Lisp style DSLs like

   var f = f1(f2(a,b,f3(c,quote(f4)))

which have a grammar backed by the full faith and credit of the Java type system. You can code gen the static imports.

[seanmcdirmid]

Eh, you can host DSLs in Kotlin and C# these days, you don’t even have to sell your engineering team on Lisp. The biggest challenge is to explain how an embedded DSL differs from being just a library (interop outside of the eDSL to the host language is still hard).