generics - nim 带有泛型的两个键表

Question

尝试在 Nim 中创建一个两键字典，其中值是用户指定的类型。

import Tables

type
  TwoKeyTable[T] = Table[string, Table[string, T]]

# initialize two key table
proc initTwoKeyTable[T](): TwoKeyTable[T] =
  result = initTable[string, Table[string, T]]()  

# check to see if keys k1 and k2 are in table
proc hasKeyPair[T](tkTable: TwoKeyTable[T], k1, k2: string): bool =
  result = false
  # check if first key is in table
  if not tkTable.hasKey(k1):
    return
  # check if second key in the tables
  if not tkTable[k1].hasKey(k2): # 1st error coming from here 
    return
  result = true

# add a value corresponding to the keys k1 and k2
proc addKeyPairValue[T](tkTable: var TwoKeyTable[T], k1, k2: string, val: T) =
  if not tkTable.hasKey(k1):
    tkTable[k1] = initTable[string, T]() # 2nd error coming from here
  tkTable[k1][k2] = val


var tkTable = initTwoKeyTable[int]()
echo tkTable.hasKeyPair("a", "b") # produces the 1st error

出现以下错误:

lib/pure/collections/tables.nim(249, 38) Error: type mismatch: got (Table[system.string, system.int]) but expected 'int

我也有这个问题。

var tkTable = initTwoKeyTable[int]()
tkTable.addKeyPairValue("a", "b", 1) # produces the 2nd error

这会产生相同的错误。

Answer 1

对我来说看起来很像一个错误，我报告了它:https://github.com/nim-lang/Nim/issues/2722

作为一种解决方法，当 TwoKeyTable 不是通用的时，它可以工作:

import Tables

type
  TwoKeyTable = Table[string, Table[string, int]]

# initialize two key table
proc initTwoKeyTable(): TwoKeyTable =
  result = initTable[string, Table[string, int]]()

# check to see if keys k1 and k2 are in table
proc hasKeyPair(tkTable: TwoKeyTable, k1, k2: string): bool =
  result = false
  # check if first key is in table
  if not tkTable.hasKey(k1):
    return
  # check if second key in the tables
  if not tkTable[k1].hasKey(k2): # 1st error coming from here
    return
  result = true

# add a value corresponding to the keys k1 and k2
proc addKeyPairValue[T](tkTable: var TwoKeyTable, k1, k2: string, val: T) =
  if not tkTable.hasKey(k1):
    tkTable[k1] = initTable[string, T]() # 2nd error coming from here
  tkTable[k1][k2] = val


var tkTable = initTwoKeyTable()
echo tkTable.hasKeyPair("a", "b") # produces the 1st error