如何修改erlang中的记录？ [英] How do I modify a record in erlang?

问题描述

  #op {
 action = [walk，from，{place}，to，{other_place}]，
 preconds = [[at，{place}，me]，[on，floor，me]，
 [ other_place，{place}，{other_place}]]，
 add_list = [[at，{other_place}，me]]，
 del_list = [[at，{place}，me]] 
} 
  

但是，erlang不允许修改变量。有没有数据类型？

解决方案

erlang不允许你修改变量是真的。但是没有什么可以阻止你修改变量的副本。

给定你的记录：

 code> Rec = #op {
 action = [walk，from，{place}，to，{other_place}]，
 preconds = [[at，{place}，me] on，floor，me]，
 [other_place，{place}，{other_place}]]，
 add_list = [[at，{other_place}，me]]，
 del_list = [[在{place}，我]] 
} 
  

您可以有效获取修改版本如下所示：

  %%替换Rec2中的操作字段，但其他所有内容与Rec相同。 
 Rec2 = Rec＃op {action = [walk，from，{new_place}，to，{new_other_place}}} 
  

这将完成你似乎在问的问题。

I to need modify the values {place} and {other_place} in the op record.

#op{
    action   = [walk, from, {place}, to, {other_place}],
    preconds = [[at, {place}, me], [on, floor, me], 
                [other_place, {place}, {other_place}]],
    add_list = [[at, {other_place}, me]],
    del_list = [[at, {place}, me]]
}

But erlang don´t allow modifying variables. Is there a data type for that?

解决方案

erlang doesn't let you modify variables it is true. But nothing prevents you from making modified copies of a variable.

Given your record:

Rec = #op{
    action   = [walk, from, {place}, to, {other_place}],
    preconds = [[at, {place}, me], [on, floor, me], 
                [other_place, {place}, {other_place}]],
    add_list = [[at, {other_place}, me]],
    del_list = [[at, {place}, me]]
}

You can effectively get a modified version like so:

%% replaces the action field in Rec2 but everything else is the same as Rec.
Rec2 = Rec#op{action = [walk, from, {new_place}, to, {new_other_place}]}

This will accomplish what you seem to be asking.

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