Is D programming friendly for beginners?

[Quirin Schroll]

On Monday, 4 March 2024 at 13:37:53 UTC, Fidele wrote:
> Is D programming friendly for beginners?

Only if you use `@safe` on your `main` function and essentially 
everywhere except templates (those infer `@safe` and you should 
let them do that). `@system` is an expert tool, unfortunately, 
it’s the default. Unless you use `@safe`, it is actually easy to 
accidentally corrupt memory. For short, `@safe` disallows any 
operation that could introduce undefined behavior, in particular 
memory corruption.

There are so-called preview switches on the compiler. Those 
enable latest features or bugfixes that are incompatible with the 
old langue state. If a preview feature is deemed ready for 
production, it’ll become active by default. IMO, the following 
preview switches should be enabled:
* `-preview=dip1000` This allows more operations in `@safe` code, 
but error messages can become more cryptic. E.g., pre-DIP1000, 
taking the address of a local variable was illegal and with 
DIP1000, it’s allowed under certain circumstances, but when it’s 
not okay, the error message isn’t simply “you can’t do that”. It 
will become the default at some point, so it might be worth to 
learn its semantics from the beginning.
* `-preview=dip1008` Allows allocating `Error` objects in `@nogc` 
code. Makes `@nogc` code more useful.
* `-preview=fieldwise` Must have. Fixes auto-generated 
comparisons for structs.
* `-preview=fixAliasThis` Fixes lookup of `alias this` constructs.
* `-preview=nosharedaccess` Must have. Fixes `shared`, which can 
be unsafe otherwise.
* `-preview=in` Makes the parameter storage class `in` actually 
useful. Note: This is dangerous without `@safe`. Under the 
preview switch, `in` makes strong guarantees, but without 
`@safe`, it is assumed, but not checked, if the guarantees truly 
hold. With `@safe`, however, they are checked and it’s fool-proof.
* `-preview=inclusiveincontracts` Must have. Fixes function 
contracts.
* `-preview=fixImmutableConv` Must have. Fixes various conversion 
issues in the type system.

Not actively recommended, but not actively harmful either:
* `-preview=bitfields` Unclear if it’s going to stay.
* `-preview=systemVariables` Primarily relevant if you write 
`@system` code. First learn the language. (No harm if enabled.)

Recommended to stay away from:
* `-preview=rvaluerefparam` Don’t use it. It’s never going to be 
the default and likely will be removed in the future in favor of 
something else.

The reason I’m advocating preview switches is because as a 
learner, you’re likely not writing production code that’s going 
to stay, but throwaway code for the purpose of you gaining 
knowledge of the language.