Re: Further C++ operators for position

> On 4 Nov 2019, at 18:12, Akim Demaille <[email protected]> wrote:
> 
>> Le 4 nov. 2019 à 17:03, Matthew Fernandez <[email protected]> a écrit :
>> 
>> The std::less implementation you suggest is to also lexicographically compare the filenames themselves? I’m not sure this makes sense, because source positions from two different files aren’t really orderable at all.
> 
> The point of defining std::less is to have an easy means to insert positions in a sorted container, say std::map.  Now, the order in itself is well defined, but my not reflect the order the user would like to see.
> 
> To be clear: I don't have a problem with std::less which I see as an implementation detail, but operators such as <= and the like are different: they express a total order that we can't implement easily.  

The total order is expressed via std::less in containers such as std::map, with undefined results if not fulfilling the specs for that.

> In addition, think of C where you also have main.c that #include "foo.h" somewhere, which results in main.c:1 (i.e., line 1) < foo.h:1 < ... < foo.h:42 < ... < main.c:3.

Here the files are stacked, and if the nested files are closed after being read, the location pointers are dead.

> If we want a total order here, it's actually easy: positions should have a counter somewhere which is the *total* "offset" since the first byte of the first file.  Or something like that.