the intern function and the Shen type system

[Antti Ylikoski]

Could it be possible to include the intern function in the Shen type
system?

I mean the below behavior:

------------------------------------------------------------

antti@antti-HP-Compaq-6715s-GR618ES-AK8:~/shen$ shen

Shen, copyright (C) 2010-2015 Mark Tarver
www.shenlanguage.org, Shen 20.0
running under Common Lisp, implementation: SBCL
port 2.0 ported by Mark Tarver


(0-) (intern "sym1")
sym1

(1-) (tc +)
true

(2+) (intern "sym2")
type error


(3+) (exit 0)
antti@antti-HP-Compaq-6715s-GR618ES-AK8:~/shen$

------------------------------------------------------------

yours, AJY
Finland, the EU

[Mark Tarver]

Not really; interning can generate a boolean as well as a symbol.

Mark

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[Thomas Bartscher]

Didn't try it out, but as a first step I'd go for an either type:

(deftype either
  A: T
  ____
  A: (either T _)

  A: T
  ____
  A: (either _ T))

I'm sure this is horribly inadequate, but I haven't used Shen for quite a while now.
With this, the type of intern would be
{ --> (either symbol boolean)}
This would require additional clauses in the above type definition to discern type based on where clauses somehow and using it in code would require using these where clauses, but I think saying that a type secure intern isn't possible is a bit early.

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