cca@pur-phy (Charles C. Allen) (09/27/88)
In this discussion of pointers and data structures, I hope that people will occasionally pause to take a somewhat broader view of things (beyond what they think should go in FORTRAN 8x). Yes, FORTRAN has very little in the way of data structuring facilities, and yes, pointers are one way to build those, and yes, pointers as implemented in C can be dangerous. Languages do exist that have the sort of structures people have been talking about, without resorting to pointers and all their difficulties. Smalltalk, for example, has classes called OrderedCollection (stacks and queues), SortedCollection, Set, Bag, Dictionary (essentially keyed hash tables), and MappedCollection (mappings of one collection to another). I'm not suggesting Smalltalk as a substitute for FORTRAN (at least, not yet :-), just that other people have looked at this sort of thing before and come up with solutions that bear looking at. Charlie Allen cca@newton.physics.purdue.edu
ok@quintus.uucp (Richard A. O'Keefe) (09/28/88)
In article <1475@pur-phy> cca@pur-phy (Charles C. Allen) writes: >In this discussion of pointers and data structures, I hope that people >will occasionally pause to take a somewhat broader view of things ... >Languages do exist that have the sort of structures people have been >talking about, without resorting to pointers and all their >difficulties. Smalltalk, for example, ... It is worth noting that most such languages notionally make _everything_ a pointer. (SETL is an exception.) Smalltalk-80, for example, has that amazing operation "become:". The distinction between pointer-based and value-based views come up when you consider assignment. Simula 67, for example, had two assignment operators: Lhs := Rhs; !copy the value of Rhs onto the storage of Lhs; Lhs :- Rhs; !make Lhs point to whatever Rhs points to; If I understand the Fortran 8X ALLOCATE stuff correctly, since array assignment copies the contents of the source to the destination, and since no methods are provided for copying the pointer, it is providing a value-based model rather than a pointer-based one. But the allocation status of the hidden pointer variable is still important.