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Lies in education [was Re: The "loop and a half"]


On 11/10/2017 23:03, Gregory Ewing wrote:
> bartc wrote:
> 
>> ??? tokenrec * (*)[]
>  >
>> the original source and that type is written like this:
>>
>> ??? ref [] ref tokenrec
> 
> The idiomatic way to write that type in C would be
> 
>  ?? tokenrec **

The original has an extra pointer so idiomatic C might be more:

     tokenrec ***

But this still defines a different type, namely:

     pointer to pointer to pointer to tokenrec

not:

     pointer to array of pointer to tokenrec

If you want to lose all array information, and really don't care if 
you're dealing with a pointer, or an array (and don't mind changing how 
such a value is passed, and how it is accessed) then this is fine for you.

You just have to access a 'tokenrec ***args' parameter as ***args. Or 
**args[i]. Or *args[i][j]. **(args[i]). Or ***args. Or args[i][j][k]. 
Yes, any combination will work! Only one will be correct.

In the original source, it can only be accessed one way - the correct 
way. Using the non-idiomatic 'tokenrec *(*)[]' in C imposes some extra 
constraints, but doesn't do the full job. However my complaint was about 
the syntax; the type system of C is another subject.

(How I ended up talking about C in this group I don't know. But 
yesterday I mentioned Python in the C group, so ...)

-- 
bartc