[PRL] symbology question

[Dave Herman]

Maybe "T ~: U"? That's not too bad. It makes the analogy to <: via the 
colon, the colon indicates the asymmetry, and the tilde suggests 
"not-quite-the-same-as". And there's no suggestion of transitivity (as 
opposed to symbols based on "<") or computation (as opposed to arrow 
symbols).

Plus it looks like a little tadpole. Aww.

Dave

Dave Herman wrote:
> What would be a good mathematical symbol for representing a relation 
> between types that is neither symmetrically nor transitively closed? 
> Specifically, it represents a relation whose interpretation is "T may be 
> cast to U under a conversion".
> 
> I originally was using #\u2272 ("LESS-THAN OR EQUIVALENT TO") -- see
> 
>     http://www.alanwood.net/unicode/mathematical_operators.html
> 
> I liked the squiggly for suggesting "T and U are sort of the same", but 
> I'm afraid the "less-than" connection suggests transitivity. I'm 
> intrigued by:
> 
>     #\u22B0 ("PRECEDES UNDER RELATION")
> 
> but it may suffer the same problem -- "precedes" probably implies 
> transitivity. I could use some sort of squiggly or curly arrow, but then 
> it starts to look more like a reduction relation.
> 
> Thanks,
> Dave "Johan Ovlinger" Herman
> 
> 
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