3
$ coqtop -v
The Coq Proof Assistant, version 8.4pl5 (February 2015)
compiled on Feb 06 2015 17:44:41 with OCaml 4.02.1
予定义的下列CoInductive
类型,stream
:
$ coqtop
Welcome to Coq 8.4pl5 (February 2015)
Coq < CoInductive stream (A : Type) : Type :=
Coq < | Cons : A -> stream A -> stream A.
stream is defined
Coq < Check stream.
stream
: Type -> Type
Coq < Check Cons.
Cons
: forall A : Type, A -> stream A -> stream A
然后,我试图定义以下CoFixpoint
定义,zeros
:
Coq < CoFixpoint zeros : stream nat := Cons 0 zeros.
然而,我得到了以下错误:
Toplevel input, characters 38-39:
> CoFixpoint zeros : stream nat := Cons 0 zeros.
> ^
Error: In environment
zeros : stream nat
The term "0" has type "nat" while it is expected to have type
"Type".
我想通了,我必须显式实例变量A
:
Coq < CoFixpoint zeros : stream nat := Cons nat 0 zeros.
zeros is corecursively defined
为什么不勒柯克本身推断A
类型?我如何使其推断A
的类型?
旁注隐含参数的更多信息:项目2.和3.声明'A'为[最大插入(HTTPS://coq.inria。 fr/refman/Reference-Manual004.html#Implicit%20Arguments)参数。使用“设置隐式参数”指令推断的隐式参数未声明为最大可插入。因此,如果适用,可能需要添加“设置最大隐式插入”。 –