5 feb 2012 kl. 17.24 skrev Rob Arthan:
> On 5 Feb 2012, at 11:51, David Matthews wrote:
>
>> On 03/02/2012 15:44, Phil Clayton wrote:
>>> It appears that Poly/ML overloads operators + - < <= >= > for Time.time
>>> but they shouldn't be, according to the Basis Library.
>>> http://www.standardml.org/Basis/top-level-chapter.html#section:3
>>> Perhaps they were overloaded once upon a Time.time...
>>
>> Yes, it looks as though strictly speaking you're right. It does seem
>> strange, though, to have these operators and not include them in the
>> overloading. I'm rather reluctant to remove the overloading but I
>> appreciate as it stands it doesn't comply with the definition.
>
> This must have been just an oversight in the Basis Library design. It is
> crazy that opening the structure Time.Time prevents you using the natural
> syntax for arithmetic on the real and integer types that you use to construct
> values of the abstract type the structure implements.
That is because of the semantics of Open and has nothing to do with Time
specifically. Opening any library which has its own versions of the overloaded
math operations will remove the overloading. Witness:
Poly/ML 5.4.1 Release
> open Real;
[...output omitted....]
> 1+1;
Error-Type error in function application.
Function: + : real * real -> real
Argument: (1, 1) : int * int
Reason:
Can't unify int (*In Basis*) with real (*In Basis*)
(Different type constructors)
Found near 1 + 1
Static Errors
Lars-Henrik Eriksson, PhD, Senior Lecturer
Computing Science, Dept. of Information Technology, Uppsala University, Sweden
E-mail: [email protected], Web: http://www.it.uu.se/katalog/lhe?lang=en
Phone: +46 18 471 10 57, Mobile: +46 705-36 39 16, Fax: +46 18 51 19 25
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