On 9/20/10 11:09 AM, Graydon Hoare wrote:
Is it possible to infer the type from the expression, e.g. in 2 + x
the 2 matches the declared type of x?
Plausible. Go takes a similar angle on this; their numeric literals are
"untyped" and acquire a type via inference from the context. I'm not
sure I'm really keen on that -- every additional complication to
inference is a bit of a penalty to implementers, tools and future
readers -- but it could work.
Any feelings from others? Particularly .. those who have worked on the
type inference module :)
I'm also somewhat opposed to the proposal. To me, the strict typing of
numeric literals is a great feature of Rust: it lets the programmer look
at the code and immediately tell what's going to happen in the generated
instructions and memory layout. C's integer promotion rules are
confusing; by looking at C code I can never really tell precisely which
instruction is going to be emitted.
Adding Go-style untyped numeric literals would also be difficult to
reconcile with our type inference and polymorphic binary operators:
what's the type of x in "auto x = 2 + 3;"?
Patrick
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