[jftuga]

This reminds me of some silly C code I once wrote for fun, which counts down from 10 to 1:

    #include <stdio.h> // compile & run: gcc -Wall countdown.c -o countdown && ./countdown
    int n = 10; int main(int argc, char *argv[]) { printf("%d\n", n) && --n && main(n, NULL); }

Python version:

    import sys # run: python3 countdown.py 10
    def main(n:int): sys.stdout.write(f"{n}\n") and n-1 and main(n-1)
    main(int(sys.argv[1]))

Shell version:

    # run ./countdown.sh 10
    echo $1 && (($1-1)) && $0 $(($1-1))

[quietbritishjim]

Nitpick: you could replace sys.stdout.write(f"{n}\n") with print(n). The current code looks very much like it was written for Python 2 (apart from the f string!), where print was a statement. As of Python 3, print is just a regular function. It returns None, which is falsey, so you'd also need to change your first "and" to an "or".

[jftuga]

Thanks for this suggestion - it works great.

    import sys # run: python3 countdown.py 10
    def main(n:int): print(n) or n-1 and main(n-1)
    main(int(sys.argv[1]))

This also works and is definitely more Pythonic:

    _ = [print(n) for n in range(10,0,-1)]

[cbrpnk]

I don't think I've ever thought of explicitly calling main(). Made me chuckle.

[akdev1l]

I think it is UB

Edit: actually looks like it is UB in C++ but not C

[colejohnson66]

Why would calling main be UB!? How is crt0 supposed to work?

[tomjakubowski]

crt0 generally isn't C and isn't subject to C's rules

[astrange]

malloc() can't be implemented in C either because it's defined as doing things (creating new memory objects) there are no lower level mechanisms in C to do.

[eacnamn]

all malloc is defined to do is to return a pointer to storage of appropriate size and alignment, which can easily be done in pure standard C by defining a static array and chopping it up as needed. that's not a brilliant way of doing that, but achievable without leaving standard C

[akdev1l]

As the other person pointed out, anything that happens before main is strictly not covered by the C standard.

Even things like “printf” can’t be implemented purely in standard C. Even making a syscall is outside of the scope of the C standard.