kenkel@mcnc.UUCP (Stephen Kenkel) (06/24/86)
The following program compiles under VMS fortran, but not
f77:
dimension l(10),m(10),n(10)
write (*, * ) i,((l(k), m(k), n (k)), k=1,10)
end
This version works:
dimension l(10),m(10),n(10)
write (*, * ) i,(l(k), m(k), n (k), k=1,10)
end
The extra parenthesis around the items in the implied do list
appears to be causing trouble. Is this a bug, or is the compiler
in compliance with the standard?
Thanks.ark@alice.UucP (Andrew Koenig) (06/25/86)
> The following program compiles under VMS fortran, but not > f77: > > dimension l(10),m(10),n(10) > write (*, * ) i,((l(k), m(k), n (k)), k=1,10) > end > > This version works: > > dimension l(10),m(10),n(10) > write (*, * ) i,(l(k), m(k), n (k), k=1,10) > end > > The extra parenthesis around the items in the implied do list > appears to be causing trouble. Is this a bug, or is the compiler > in compliance with the standard? > > Thanks. The compiler is in compliance with the standard. The list of expressions in an implied DO must not be parenthesized. Otherwise there would be an ambiguity: write (*,*) ((3.0,4.0), k = 1, n) Does this print ten alternating repetitions of 3.0 and 4.0, or is (3.0,4.0) a complex constant?
steved@sun.uucp (Steve Dever) (06/25/86)
In article <1452@alvin.mcnc.UUCP> kenkel@mcnc.UUCP (Stephen Kenkel) writes: >The following program compiles under VMS fortran, but not >f77: > > dimension l(10),m(10),n(10) > write (*, * ) i,((l(k), m(k), n (k)), k=1,10) > end > The ANSI FORTRAN standard (section 12.8.2.3) states that an implied DO list has the form: (dlist, i = e1, e2 [, e3]) where dlist is an input/output list. The standard does not allow an extra set of parentheses around an I/O list in a READ or WRITE statement so the compiler is correct in not accepting them. This was allowed in the FORTRAN-66 standard but was removed to eliminate the syntactic conflict with complex constants in a list-directed output list. Steve Dever (sun!steved)
steve@jplgodo.UUCP (06/26/86)
In article <1452@alvin.mcnc.UUCP>, kenkel@mcnc.UUCP (Stephen Kenkel) writes: > The following program compiles under VMS fortran, but not f77: > > dimension l(10),m(10),n(10) > write (*, * ) i,((l(k), m(k), n (k)), k=1,10) > end > > This version works: > > dimension l(10),m(10),n(10) > write (*, * ) i,(l(k), m(k), n (k), k=1,10) > end > > The extra parenthesis around the items in the implied do list > appears to be causing trouble. Is this a bug, or is the compiler > in compliance with the standard? It looks like f77 is complying with the standard and VMS Fortran has relaxed the requirements. Quoting from the ANSI standard: 12.8.2.3 Implied-DO List. An implied-DO list if of the form: ( dlist, i = e1, e2 [,e3] ) where: i, e1, e2, and e3 are as specified for the DO statement (11.10) dlist is an input/output list ....... 12.8.2 Input/Ouput List. ..... An input/output list is a list (2.10) of input/output list items and implied-DO lists (12.8.2.3). An input/output list item is either an input list item or an output list item. ..... 12.8.2.2 Output list items. An output list item must be one of the following: (1) A variable name (2) An array element name (3) A character substring name (4) An array name (5) Any other expression except a character expression involving concatenation of an operand whose length specification is an asterisk in parentheses unless the operand is the symbolic name of a constant. Note that a constant, an expression involving operators or function references, or an expression enclosed in parentheses may appear as an output list item but must not appear as an input list item. 2.10 List A list is a nonempty sequence (2.1) of syntactic entities seperated by commas. The entities in the list are called list items. Essentially, the stuff after the ( in an implied-DO list before the indexing information must be a valid I/O list. The only time parentheses are allowed in an I/O list is surrounding an expression or surrounding an implied-DO list. A sequence of things seperated by commas is certainly not a valid Fortran expression. Since there is no loop index information given, it is not a valid implied-DO list either. Therefore it is not a valid I/O list item. Editorial remark: It has been my experience that VMS Fortran is *very* liberal in what it will accept as valid Fortran. If you care at all about being portable, get a copy of the ANSI standard and throw away your vendor's manuals. The other recommendation I would make is to always use the /STANDARD qualifier when you compile on a VAX. This should flag most of the non-standard extensions you are using. I don't know how picky this is on a VAX since all of my developement work is done on a Ridge but it should help. -- ...smeagol\ Steve Schlaifer ......wlbr->!jplgodo!steve Advance Projects Group, Jet Propulsion Labs ....logico/ 4800 Oak Grove Drive, M/S 156/204 Pasadena, California, 91109 +1 818 354 3171
cathy@comp.lancs.ac.uk (Cathy) (07/01/86)
In article <1452@alvin.mcnc.UUCP> kenkel@mcnc.UUCP writes: >The following program compiles under VMS fortran, but not >f77: > > dimension l(10),m(10),n(10) > write (*, * ) i,((l(k), m(k), n (k)), k=1,10) > end > >This version works: > ... > >The extra parenthesis around the items in the implied do list >appears to be causing trouble. Is this a bug, or is the compiler >in compliance with the standard? > The compiler seems to agree with the standard. The syntax is: io_implied_do_list : "(" io_list "," id "=" exp "," exp [ "," exp ] ")" ; io_list : io_entity ( "," io_entity )* ; io_entity : array_variable | io_implied_do_list ; The extra bracket would imply an internal io_implied_do_list. Best wishes, Cathy -- - Marxist unite! - Leaders unite! - Bad-spellers of the of the world untie! UUCP: ...!seismo!mcvax!ukc!dcl-cs!cathy DARPA: cathy%lancs.comp@ucl-cs | Post: University of Lancaster, JANET: cathy@uk.ac.lancs.comp | Department of Computing, Phone: +44 524 65201 ext ???? | Bailrigg, Lancaster, LA1 4YR, UK.