使用一个字段创建Ada记录 [英] Creating Ada record with one field

问题描述

我定义了一个类型：

type Foo is record
   bar : Positive;
end record;

我想创建一个返回记录实例的函数：

I want to create a function that returns an instance of the record:

function get_foo return Foo is
    return (1);
end get_foo;

但是Ada不会让我说位置合计不能有一个论点。

愚蠢地尝试，我在记录中添加了另一个哑字段，然后 return（1，DOESNT_MATTER）; 起作用！

But Ada won't let me, saying "positional aggregate cannot have one argument".
Stupidly trying, I've added another dumb field to the record, and then return (1, DOESNT_MATTER); works!

我如何告诉Ada不是位置汇总，而是尝试创建记录？

How do I tell Ada that's not a positional aggregate, but an attempt to create a record?

推荐答案

位置聚合初始化不能用于只有一个成分的记录，但这并不意味着您不能具有一个成分的记录。

The positional aggregate initialization cannot be used with record having only one component, but that does not mean you cannot have record with one component.

记录类型的值是通过给出命名字段列表来指定。 get_foo 函数的正确代码应如下所示。

The values of a record type are specified by giving a list of named fields. The correct code for your get_foo function should be as following.

function get_foo return Foo is
    return (bar => 1);
end get_foo;

还可以使用 Foo'（bar => 1）表达式。

实际上，使用命名组件列表要比位置初始化更好。您可以忘记组件的位置，并且如果在记录中添加新字段，该位置也不会改变。

Using the list of named components is better in practice than positional initilization. You can forget the position of the component and it does not change if you add a new field into your record.

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