Injective type families

[Roman Cheplyaka]

* Kim-Ee Yeoh <ky3 at atamo.com> [2014-07-10 23:40:44+0700]
> On Thu, Jul 10, 2014 at 9:37 PM, Jan Stolarek <jan.stolarek at p.lodz.pl>
> wrote:
> 
> > 1. Standard injective type family (all parameters uniquely determined by
> > the RHS):
> >    injective type family F a b c | a b c
> >
> > <snip>
> >
> >  2. Type family injective only in some parameters (ie. only some
> > parameters uniquely determined by the RHS):
> >    injective type family G a b c | a b
> >
> 
> English is not my mother tongue. Perhaps you mean: 'the image under the
> type function is uniquely determined by the parameters on the right of the
> vertical bar'?

The result of any function is always determined by that function's parameters.

Injectivity means that the *parameters* are determined by the result.

So I think Jan's definition is correct.

> As they stand, the sentences confuse which determines what.
> 
> Such confusion has a way of squirreling into official documentation.
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