从动态作用域更改为静态作用域/词法作用域

Question

如何更改big_step_Decls (Proc p s)以遵循静态作用域规则并匹配proc类型？

这是我想实现的静态proc声明的规则：

<decls, env [p -> (s, env)] --> <sto', env'>
------------------------------------------------
<proc p is s : decls, env, sto > --> <sto', env'>

这是Haskell代码的一个片段，用于变量和过程声明的大步语义。

data Env = Env {var :: Map String Loc, proc :: Map String (Stm, Env)} deriving Show

env0 = Env { var = empty, proc = empty}


big_step_Decls :: ([Decl], Env, Sto) -> (Env, Sto)

big_step_Decls ([], env, sto) = (env, sto)

big_step_Decls ((VarD x a): more_decls, env, sto) = (env', sto')
   where v = big_step_a env sto a'
         (l, sto'') = alloc sto
         env'' = env {var = insert x l (var env)}
         (env', sto') = big_step_Decls (more_decls, env'', insert l v sto'')

big_step_Decls ((Proc p s): more_decls, env, sto) = (env',sto')
   where env''  = env {proc = insert p s (proc env)}
         (env', sto') = big_step_Decls (more_decls, env'', sto)

这就是我得到的错误(附言:我是Haskell的新手，还在努力弄清楚基础知识。)

BIPs.hs:161:31: error:
    * Couldn't match type `Stm' with `(Stm, Env)'
      Expected type: Map String (Stm, Env)
        Actual type: Map String Stm
    * In the `proc' field of a record
      In the expression: env {proc = (insert p s) (proc env)}
      In an equation for env'':
          env'' = env {proc = (insert p s) (proc env)}
    |
161 |    where env''  = env {proc = (insert p s) (proc env)}
    |                               ^^^^^^^^^^^^^^^^^^^^^^^

BIPs.hs:161:45: error:
    * Couldn't match type `(Stm, Env)' with `Stm'
      Expected type: Map String Stm
        Actual type: Map String (Stm, Env)
    * In the third argument of `insert', namely `(proc env)'
      In the `proc' field of a record
      In the expression: env {proc = (insert p s) (proc env)}
    |
161 |    where env''  = env {proc = (insert p s) (proc env)}
    |                                             ^^^^^^^^
Failed, no modules loaded.

Answer 1

在此表达式中，env'' = env {proc = (insert p s) (proc env)} p是映射键，s是值。proc映射中的值具有类型(Stm, Env)，但您当前仅尝试插入类型为Stm的s。

所以你需要传递一个额外的环境来编译你的代码。类似于：

env'' = env {proc = insert p (s, env) (proc env)}

我不知道这在你的程序中是否有意义:-)。