That is correct. The concrete syntax will be python-like. Somer examples are here:

https://github.com/robertmuth/Cwerg/tree/master/FrontEnd/Con...

Precedent for Python-like but C-level language in Nim; will be interested to see how yours develops too. Good luck!

IIRC, wasn't this originally also the case for Lisp?

I wonder how hard it would be to keep the S-expression syntax when the new one is implemented. As a C and Lisp programmer I'm intrigued by the possibilities - C-family syntax being IMO more readable, but Lisp providing unparalleled (in my experience) metaprogramming possibilities.

I'm also a Lisp and C programmer (want to get better at Forth too).

I think Lisp and C (not C++) share an important characteristic that few other languages share: being low-level.

C is low-level due to minimal abstractions from the hardware.

Lisp is low-level due to minimal abstractions from the AST.

People wanting to program very close to hardware feel comfortable with C. People wanting to program very close to the compiler feel comfortable with Lisp.

I am planning to make the s-expr form the on disk format.

Does that mean you are planning a specific editor for it?

I was thinking more of some light weight tools that convert between the two representations and which can be hooked into existing editors.

I see. And this led me to a question: what can make a language expressed in S-expressions not a lisp?

Any language can be expressed in S-expressions. A translation of the syntax tree to sexprs is often used in parser debugging. And Lisp doesn’t have to be expressed in S-expressions (see Dylan, or M-expressions, a syntax for Lisp that predates S-expressions).

Lisp traditionally has these features, but they’re separate features:

* There is a rich syntax for literal data structures

* Code is directly exposed as data structures so it can be manipulated with code (macros)

* Code is written as literal data structures so it has no separate syntax

> Lisp traditionally has these features

Lisp has traditionally a two stage syntax

1) S-expressions

2) Lisp

S-Expression level has a syntax to describe data: lists, conses, numbers, symbols, strings, arrays, ...

Lisp syntax is defined on top of that, as s-expressions: variables, function calls, macro calls, special forms (using quote, let, if, progn, setq, catch, throw, labels, flet, declare, ...), lambda expressions. Each macro also can implement syntax.

Thanks. Can you please elaborate some bits on what is meant under "rich syntax for literal data structures"? I'm not a lisp pro, just started studying it.

That's nothing special of Lisp. Literal data structures means that one can write down data objects like list, arrays, vectors, numbers (floats, integers, rational, complex, ...), symbols, strings, characters, records/structures, ...

Common Lisp for example:

    (berlin hamburg munich cologne)   ; a list of symbols
    #(berlin hamburg munich cologne)  ; a vector of symbols
    (1.3 1.3d6 13 #c(1 3) 1/3)        ; a list of numbers
    "Hello World!"                    ; a string
    #\H                               ; the character H
    #S(CITY :NAME BERLIN              ; a structure (aka record) of type CITY
            :COUNTRY GERMANY)
    #*1010101111                      ; a bitvector
    #2A((BERLIN GERMANY)              ; a 2d array
        (PARIS FRANCE))

Other programming languages have their own syntax for literal data (even data structures like unicode characters, hash tables, unicode strings, decimal numbers, ...) Common Lisp OTOH has an extensible reader, one can add new syntax extensions for data structures, using so-called reader macros. READ is the function to read s-expressions from text streams. It returns data objects.

> Any language can be expressed in S-expressions.

I'm not sure this is true for the C preprocessor, though, where macros can represent partial structure.

People have come up with S-expression syntaxes for C, basically to be able to write C macros in lisp. Here's one: https://voodoo-slide.blogspot.com/2010/01/amplifying-c.html

Couple of others:

c-mera: https://github.com/kiselgra/c-mera

cmacro: https://github.com/eudoxia0/cmacro

(This one one is implemented in Common Lisp for its semantics, but doesn't use a S-exp surface syntax for the code.)

sxc: https://github.com/burtonsamograd/sxc

(incomplete)

MetaC: https://github.com/mcallester/MetaC

(References Lisp in readme; doesn't use it for implementation or notation, but references ideas. Source code seems to be a core of .c files, and the rest self-hosted in its own .mc language. Somehow provides a REPL.)

Ah, now I see. Thx.