trying to understand in, inout, and ref...

[mark]

On Wednesday, 22 January 2020 at 14:23:53 UTC, Paul Backus wrote:
> On Wednesday, 22 January 2020 at 10:49:07 UTC, mark wrote:
>> Regarding generate(): allWords should never be changed 
>> (generate is called in a loop with the same allWords every 
>> time) -- so should it be `in WordSet allWords`?
>
> For parameters that shouldn't be changed, use const. So it 
> should be `const WordSet allWords`.

That single change produces (using LDC 1.19.0 - D 2.089.1):

./wordladder.d(52): Error: function wordladder.update(string[] 
ladder, int[string] words, const(int[string]) compatibles) is not 
callable using argument types (string[], const(int)[string], 
const(int)[string])
./wordladder.d(52):        cannot pass argument words of type 
const(int)[string] to parameter int[string] words
Failed: ["/home/mark/opt/ldc2-1.19.0-linux-x86_64/bin/ldmd2", 
"-v", "-o-", "./wordladder.d", "-I."]

So I've rolled it back.

>> Regarding update(): ladder and words are both modified in 
>> update -- so should they be `ref WordList ladder` and `ref 
>> WordSet words`? And if so, do I need to change the update() 
>> call in the generate() function?
>
> Yes, they should be `ref`. No, you do not have to change the 
> update() call.

I've done this but my impression from the docs is that passing 
slices and associative arrays is already done by reference so 
these aren't needed? (I can't tell yet because I haven't written 
the modifying code.)

>> compatibles is (will be) modified in generate() but not in 
>> update(), so should it be `in WordSet compatibles`?
>
> It should be `const WordSet compatibles`.

Done that and it compiles fine.

Thanks.