[Haskell-cafe] Type Synonyms
tgdavies at gmail.com
Wed Oct 10 23:06:14 EDT 2007
I was wondering the other day if type synonyms might be more useful
if they were more restricted, that is, with the definitions:
type Foo = String
type Bar = String
foo :: Foo
foo = "a foo"
bar :: Bar
bar = "a bar"
x :: Foo -> ...
x f b = ...only valid for Foo Strings...
both 'x foo' and 'x bar' type check correctly.
Wouldn't it be useful if Foo and Bar were both equivalent to String,
but Foo and Bar were not equivalent themselves?
if you are using Strings as properties of something and want
to associate the type of the property with its value, without
wrapping the String.
Would this break a transitivity property of
the type system?
Am I just suffering from laziness?
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