TCL阵列的问题 - 关键与报价 [英] tcl array question - key with quotes

问题描述

这让我感到惊讶。

>set foo("bar") 12
12
>parray foo
foo("bar") = 12
>set foo(bar) 12
12
>parray foo
foo("bar") = 12
foo(bar)   = 12

似乎字面foo是不一样的foo的。然而

it seems that the literal foo is not the same as "foo". And yet

>string length foo
3
>string length "foo"
3

我是什么没能理解。

what am I failing to understand

推荐答案

的字符只有一个单词的开头（或末尾的特殊到Tcl的解析器这是由开始一个字，当然）。事实上，如果你会把空格，你会得到一个错误：

The " character is only special to Tcl's parser at the start of a word (or the end of a word that was started by ", of course). In fact, if you'd put spaces in you would have got an error:

% set foo("b a r") 2
wrong # args: should be "set varName ?newValue?"

在那里你做了字符串长度要求的情况下，的是在单词所以它是特殊的开始。如果我们把一个额外领先的垃圾字符，我们看到的消失的特殊性：

In the case where you're doing the string length calls, the " is at the start of a word so it is special. If we put an extra leading junk character, we see that the specialness of " goes away:

% string length x"bar"
6

如果你正在做一些与数组索引复杂的，我觉得它通常是更容易把一个变量本身的元素的名称，自那时以来，它更清晰这是怎么回事（通常更容易调试过）：

If you're doing something complicated with array indices, I think it's usually easier to put the name of the element in a variable itself, since then it's clearer what's going on (and usually easier to debug too):

set idx "bar"
set foo($idx) 12

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