使用 `lmap` 过滤字符串列表 [英] Using `lmap` to filter list of strings

问题描述

假设我想从列表中获取所有 5 个字母的单词.

Suppose I want to get all the 5-letter words from a list.

set words {apple banana grape pear peach}
lmap word $words {if {[string length $word] == 5} {expr {"$word"}} else continue}
# ==> apple grape peach

我对 expr {"$word"} 的引用混乱不满意.我希望这会奏效:

I'm not happy with the quoting mess of expr {"$word"}. I was hoping this would work:

lmap word $words {if {[string length $word] == 5} {return $word} else continue}
# ==> apple

从 lmap 主体返回"字符串的优雅方式是什么?

What's an elegant way to "return" a string from the lmap body?

推荐答案

主要的选择是使用 set 或使用 string cat(假设你达到日期).为清楚起见，我将下面的示例分成多行:

The main choices are to use set or to use string cat (assuming you're up to date). I've split the examples below over multiple lines for clarity:

lmap word $words {
    if {[string length $word] != 5} {
        continue
    };
    set word
}

lmap word $words {
    if {[string length $word] == 5} {
        # Requires 8.6.3 or later
        string cat $word
    } else {
        continue
    }
}

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