Ruby：如何确定一个字符是字母还是数字？ [英] Ruby: How to find out if a character is a letter or a digit?

问题描述

本周早些时候，我刚刚开始尝试Ruby，但遇到了一些我不太会编码的事情。我正在将用Java编写的扫描仪转换为Ruby以进行类分配，并且我已经深入到本节：

I just started tinkering with Ruby earlier this week and I've run into something that I don't quite know how to code. I'm converting a scanner that was written in Java into Ruby for a class assignment, and I've gotten down to this section:

if (Character.isLetter(lookAhead))
{      
    return id();
}

if (Character.isDigit(lookAhead))
{
    return number();
}

lookAhead 是从字符串中选出一个字符（每次循环时移动一个空格），这两种方法确定它是字符还是数字，并返回适当的标记类型。我还无法找出与 Character.isLetter（）和 Character.isDigit（）等价的Ruby。 。

lookAhead is a single character picked out of the string (moving by one space each time it loops through) and these two methods determine if it is a character or a digit, returning the appropriate token type. I haven't been able to figure out a Ruby equivalent to Character.isLetter() and Character.isDigit().

推荐答案

使用与字母&匹配的正则表达式数字：

Use a regular expression that matches letters & digits:

def letter?(lookAhead)
  lookAhead =~ /[[:alpha:]]/
end

def numeric?(lookAhead)
  lookAhead =~ /[[:digit:]]/
end

这些被称为POSIX括号表达式，它们的优点是给定类别下的unicode字符将匹配。例如：

These are called POSIX bracket expressions, and the advantage of them is that unicode characters under the given category will match. For example:

'ñ' =~ /[A-Za-z]/    #=> nil
'ñ' =~ /\w/          #=> nil
'ñ' =~ /[[:alpha:]]/   #=> 0

您可以在 Ruby的正则表达式文档。

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