parameter initialization expressions
in [Fortran]
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From: Tobias Burnus on 12 Mar 2010 14:12 glen herrmannsfeldt wrote: > It is common, but not required, for the KIND values for INTEGER > and REAL to overlap. If they didn't, compilers would immediately > detect the use of a SELECTED_REAL_KIND value in an INTEGER context. > > Presumably this happens rarely enough that there haven't been > complaints to compiler writers. Even if there were, too many program(mer)s assume that kind=8 is double precision, kind=4 is default integer/default real and that integer(kind=8) exists. That goes back to the rather common REAL*8 syntax; although kind numbers do not need to be the same, many users assume they are! The NAG compiler, which uses by default different kind numbers, has consequently an option -kind=byte to allow these kind numbers. Of cause, it would be possible to add such an option to other compilers, but I doubt that that will ever become the default setting. * * * Side remark: gfortran by default does not allow assigning numbers which overflow but prints (at compile time): Error: Arithmetic overflow converting REAL(8) to REAL(4) at (1). This check can be disabled with the option -fno-range-check However, some people fail to read this error message and even ask in mailing lists what they should do ... Tobias
From: robin on 13 Mar 2010 03:05 "e p chandler" <epc8(a)juno.com> wrote in message news:hndmgu$bnk$1(a)news.eternal-september.org... | | "robin" <robin_v(a)bigpond.com> wrote in message | news:WMqmn.12597$pv.5700(a)news-server.bigpond.net.au... | > "e p chandler" <epc8(a)juno.com> wrote in message | > news:hncc0c$bgj$1(a)news.eternal-september.org... | > | | > | "Luka Djigas" <ldigas@___gmail___.com> wrote in message | > | news:9n9jp5pge81lpmv4qfk810rugdbqupvike(a)4ax.com... | > | > | > | > I find this part terribly confusing. Not your answer per se, but the | > part | > | > about reals and integers. | > | > If a parameter is declared as real, shouldn't it be considered as such | > | > even with the | > | > dot missing ? | > | | > | But that does not make sense, though I too was confused by the | > | | > | d=1_dp / 2_dp | > | | > | I have learned that the types of operands on the right are not promoted | > to | > | (or related to) the type of the variable on the left. Instead, 1/2 is | > | truncated to 0 and assigned to d. | > | | > | Suppose for the sake of argument that we want this type of error to be | > | detected. dp is of type integer. Any other integer that evaluates to a | > valid | > | kind for an integer could be mis-used in the same way without producing | > an | > | error. | > | Yet "dp" is not bound in any way to type "real". There is no type in | > Fortran | > | such as "kind_specifier_of_real". Perhaps there should be, but now it's | > | probably too late as that would break existing code unless some *new* | > | inquiry functions were added to the language that returned enumerators | > of | > | the proper "type". (Sorry about that!) | > | > There's no need whatsoever for anything like that. | > | > All that is required is for vendors to use different kind numbers | > for EVERY kind type. | > | > This is perfectly permissible, since the kind numbers are entirely | > arbitrary. | > | > Thus, the problem could be solved virtually immediately. | | OK. But I don't think the language standards will ever be written at that | level of detail. [smile]. It's an implemntation issue. It doesn't need a directive from the standard, but it certainly would help.
From: robin on 15 Mar 2010 20:57
"Tobias Burnus" <burnus(a)net-b.de> wrote in message news:4B9A9209.3030702(a)net-b.de... | glen herrmannsfeldt wrote: | > It is common, but not required, for the KIND values for INTEGER | > and REAL to overlap. If they didn't, compilers would immediately | > detect the use of a SELECTED_REAL_KIND value in an INTEGER context. | > | > Presumably this happens rarely enough that there haven't been | > complaints to compiler writers. | | Even if there were, too many program(mer)s assume that kind=8 is double | precision, kind=4 is default integer/default real and that | integer(kind=8) exists. Any assumption like that makes the code non-portable. |