[m-dev.] Inductive goals

Peter Schachte pschachte at gmail.com
Thu Jan 23 19:52:48 AEDT 2014

On 23/01/14 19:12, Mark Brown wrote:
> On Thu, Jan 23, 2014 at 1:20 PM, Peter Schachte <pschachte at gmail.com> wrote:
>> The keyword 'maps' seems a bit quirky.  Why not 'in'?  It reads much
>> more naturally.
> Given the semantics, 'maps' and 'folds' are both instances of 'in'. I
> needed to distinguish the two cases so the syntax is unambiguous, and
> I thought the analogy with the map and fold predicates was reasonable.

I didn't see an 'in' in the proposal, so I don't see why you can't use
'in' as a generator.

This proposal is reminiscent of list comprehensions, where the maps and
folds constructs are analogous to the generator expressions.  Hence the
proposal for incorporating filtering.

>> Having "do true" on the end may be reasonably common; you could make the
>> 'do' optional, and true the default goal.
> That would lead to a "dangling do" problem. You don't want to go there.

What associativity did you plan for 'for' to have?  I assumed it would
be such that nested fors would need to be parenthesised, in which case
dangling dos can't happen.

Peter Schachte               In theory, theory and practice are the
University of Melbourne      same, but in practice they are not. --
schachte at unimelb.edu.au      Keith Rollins
Phone: +61 3 8344 1338

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