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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.unix.shell,comp.unix.programmer,comp.lang.misc
Subject: Re: Command Languages Versus Programming Languages
Date: Fri, 29 Mar 2024 21:06:58 -0000 (UTC)
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On Fri, 29 Mar 2024 08:09:46 -0300, Johanne Fairchild wrote:

> Consider looking at a shell language like a domain-specific programming
> language.  A shell is a programming language made specifically for
> running programs. ...  (Of course, the idea evolves and you want to
> glue programs, do variable substitution et cetera.)

That’s the thing. The design for a “language made specifically for running 
programs” always seems to start with the assumption that what the user 
types is to be passed as literal text, unless special markers are present 
to indicate that they want to “glue programs, do variable substitution et 
cetera”. Notice your use of the term “variable substitution”, which is 
characteristic of a shell language: in a programming language, you don’t 
call it “substitution”, you call it “evaluation”.

> A scripting language is a programming language made for a hypothetical
> machine, not too different from a programming language made for a real
> machine, one made of hardware.

In our CS classes we learned to think about “abstract machines”, and 
forget the distinction between “software” and “hardware”. Instead, we 
build layers of abstract machines, one on top of the other, getting more 
and more specialized towards the particular class of problems we want to 
solve at any particular time.

Command languages are just another such “abstract machine”, and the 
scripts we write in them are another layer on top.

The layering only stops when you get to a GUI; they can’t be used to build 
any further “machines” on top.

> You seem to find trouble with using a programming language in a REPL.

I find REPLs annoying and inconvenient. If I want to do “scratchpad” 
programming, I do it in a Jupyter notebook.