On Sat, Mar 21, 2009 at 12:08 PM, Achim Schneider <bars...@web.de> wrote:
> Conal Elliott <co...@conal.net> wrote: > > > > > > > yes, but dodgy isn't Bool, it's _a_ Bool. > > > > > > Right. dodgy is _a_ Bool, and therefore its meaning is an element of > > the meaning of Bool. If _any_ element of Bool (e.g. dodgy) has a > > machine-dependent meaning, then the meaning of Bool itself much have a > > complex enough structure to contain such an element. > > > Then, yes, every Haskell type depends on whatever any type depends on, > and the only way for the denotations not to explode into one's face is > to abstract away the fact that an expression forces its context upon > its continuation. "MachineInfo ->" can be added by the denotation of > function application, there's no need to have it inside Bool's > denotation. Maybe what you're saying is that the meanings of the strictly boolean building blocks (True, False, &&, ||, not) don't do anything interesting with machine-info. They just pass it along in a totally standard way that can be abstracted out. If so, I agree. And still, dodgy does have type Bool, so the meaning of Bool (the corresponding semantic domain) must have room in it for the meaning of dodgy, i.e., for machine-dependence (and compiler-dependence). The principle I'm assuming is that the meaning of a well-typed expression inhabits the meaning of the expression's type. (BTW, this principle explains what's unsafe about unsafePerformIO.) - Conal
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