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[davidb]

Maxloc and minloc intrinsics should return a scalar when the array has rank of 1 and DIM=1 is used. In the following code, the call at (A) returns an integer scalar which is assigned to the value of max_index. At (B) the value of the array element max_index is printed out.

However, when the two operations are combined at (C) (using maxloc to get the index but without using an intermediate variable) I get a compiler error. The compiler thinks the RHS is an array.

I know this seems a rather convoluted way to get the maximum (I could just use maxval), but actually in my application I am using maxloc and minloc to get indices of doubly indexed array sections like.

ind = ix(maxloc(x(ix(lower:upper)),1)+lower-1)

which exhibits the same bug but is harder to follow.

The example below is simpler.

[tk]

I'm no wiser than you are in terms of what goes on within the compiler and machine during conversion from array to scalar data when the rank is specified to be 1.
But it is clear than when maxloc(x(1:5), 1) is used an an index to an array-typed variable, it is not "seen" by the compiler as a "normal" integer.

So you need a workaround.

INT function does not change the typing of the offending argument either.
It is still seen as an array . . .

[PaulLaidler]

I have noted this issue and logged it for investigation.

[PaulLaidler]

This turns out to be a programming error. i.e. the error report is correct.

maxloc always returns an array even when its size is one hence the type miss-match.

You can assign the result of maxloc to a scalar in order to generate the type conversion etc.

[davidb]

[PaulLaidler]

I meant to say that it is your programming error.

[brucebowler]

I'm not so sure... Looking at the draft standard (the only one I have),

If ARRAY has rank one, MAXLOC (ARRAY, DIM = DIM [, MASK = MASK]) is a
scalar whose value is equal to that of the first element of
MAXLOC (ARRAY [, MASK = MASK]).

and in the example code above,

max_val = x(maxloc(x(1:5), 1))

'x(1:5)' certainly looks like a rank one array, and DIM is specified. I think maxloc should be returning a scalar, not an array, in this case.

Bruce

[PaulLaidler]

OK I think you are right. If you have DIM = 1 then the result is supposed to be a scalar.

[davidb]

[JohnCampbell]

My reading of this is that Paul was right the first time. I have extracted the description of MAXLOC from the Lahey fortran documentation, which indicates that the result is an array. Assuming the Lahey documentation is correct Fortran 95 syntax ( it always has been in the past)

[PaulLaidler]

Sorry guys for this confusion. With the volume of work that I get through, I do occasionally make mistakes, hopefully not too often.

The result in this particular case needs to be a scalar and both FTN95 and Lahey have sliped up on this detail.

If I can fix the bug, I will and hopefully no ones existing code will be broken.

[davidb]

Thank you Paul.

I checked a few other compilers, NAG, Gfortran, open64 all return a scalar if DIM=1 and the array has rank 1 and comply with the draft standard.
_________________
Programmer in: Fortran 77/95/2003/2008, C, C++ (& OpenMP), java, Python, Perl

[davidb]

[JohnCampbell]

I have now looked in the latest standard that I have, and it shows 3 cases for MAXLOC, with case (iii) result being a scalar, as David has used and Bruce has indicated. However, if DIM is omitted (case (i)) then the result reverts to an array!

It's interesting to note that the standard shows the examples as
Case (i) is: The value of MAXLOC ((/ 2,6,4,6 /)) is [2], while for
Case(iii) is: The value of MAXLOC ((/ 5,-9,3 /), DIM=1) is 1

Can we take from this that "[2]" and "[2,1,2]" can be used as a valid alternative array syntax for "(/2/)" and "(/ 2,1,2 /)", as they are listed in the standard !!
If it was good enough for those who wrote the standard, why not for us users ?

John

[davidb]