They're both a variation of metaprogramming, but their semantics are slightly
different. A template is code substitution that substitutes at every invocation
whereas a generic only generates a procedure once on it's first invocation.
proc doThing(a: auto) =
mixin otherThing
otherThing(a)
template doThing2(a: auto) =
otherThing(a)
proc otherThing(a: auto) = echo a
doThing("hello")
doThing2("hello")
proc otherThing(s: string) = echo "hmm"
doThing("hello")
doThing2("hello")
Run
Demonstrates this difference, also since generic procedures are actual
procedure you can use them as pointer procedures:
var a = (proc(s: string))(doThing)
a("hello")
Run
So in reality to use a template one needs a template that emits a specific
procedure
template emitDoThing(typ: typedesc) =
proc doThing(val: typ) =
otherThing(val)
emitDoThing(string)
doThing("hello")
Run
