我必须标记条件字符串表达式:
Aritmetic运算符是= +, - ,*,/,%
布尔运算符=&&,||
条件运算符= ==,> =,>,<,< =,<,!=
示例表达式是=(x + 3> 5 * y)&&(z> = 3 || k!= x)
我想要的是标记化这个字符串=运算符+操作数。
因为“>”和“> =”和“=”和“!=”[包含相同的字符串]我在标记化方面遇到问题。
PS1 :我不想进行复杂的词法分析。只是简单地解析 如果可能的话,用reqular表达式。
PS2:或者换句话说,我寻找给出的正则表达式 样本表达式没有whitespace =
(x+3>5*y)&&(z>=3 || k!=x)
并将生成每个标记用白色空格分隔,如:
( x + 3 > 5 * y ) && ( z >= 3 || k != x )
答案 0 :(得分:4)
不是正则表达式,而是可能正常工作的基本标记器(请注意,您不需要执行string.Join
- 您可以使用IEnumerable<string>
通过foreach
):< / p>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
static class Program
{
static void Main()
{
// and will produce each token is separated with a white space like : ( x + 3 > 5 * y ) && ( z >= 3 || k != x )
string recombined = string.Join(" ", Tokenize("(x+3>5*y)&&(z>=3 || k!=x)"));
// output: ( x + 3 > 5 * y ) && ( z >= 3 || k != x )
}
public static IEnumerable<string> Tokenize(string input)
{
var buffer = new StringBuilder();
foreach (char c in input)
{
if (char.IsWhiteSpace(c))
{
if (buffer.Length > 0)
{
yield return Flush(buffer);
}
continue; // just skip whitespace
}
if (IsOperatorChar(c))
{
if (buffer.Length > 0)
{
// we have back-buffer; could be a>b, but could be >=
// need to check if there is a combined operator candidate
if (!CanCombine(buffer, c))
{
yield return Flush(buffer);
}
}
buffer.Append(c);
continue;
}
// so here, the new character is *not* an operator; if we have
// a back-buffer that *is* operators, yield that
if (buffer.Length > 0 && IsOperatorChar(buffer[0]))
{
yield return Flush(buffer);
}
// append
buffer.Append(c);
}
// out of chars... anything left?
if (buffer.Length != 0)
yield return Flush(buffer);
}
static string Flush(StringBuilder buffer)
{
string s = buffer.ToString();
buffer.Clear();
return s;
}
static readonly string[] operators = { "+", "-", "*", "/", "%", "=", "&&", "||", "==", ">=", ">", "<", "<=", "!=", "(",")" };
static readonly char[] opChars = operators.SelectMany(x => x.ToCharArray()).Distinct().ToArray();
static bool IsOperatorChar(char newChar)
{
return Array.IndexOf(opChars, newChar) >= 0;
}
static bool CanCombine(StringBuilder buffer, char c)
{
foreach (var op in operators)
{
if (op.Length <= buffer.Length) continue;
// check starts with same plus this one
bool startsWith = true;
for (int i = 0; i < buffer.Length; i++)
{
if (op[i] != buffer[i])
{
startsWith = false;
break;
}
}
if (startsWith && op[buffer.Length] == c) return true;
}
return false;
}
}
答案 1 :(得分:1)
如果你可以预定义你将要使用的所有操作符,这样的东西可能适合你。
请务必将双字符运算符放在正则表达式的前面,以便您尝试匹配'&lt;'在匹配'&lt; ='之前。
using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = "!=|<=|>=|\\|\\||\\&\\&|\\d+|[a-z()+\\-*/<>]";
string sentence = "(x+35>5*y)&&(z>=3 || k!=x)";
foreach (Match match in Regex.Matches(sentence, pattern))
Console.WriteLine("Found '{0}' at position {1}",
match.Value, match.Index);
}
}
输出:
Found '(' at position 0
Found 'x' at position 1
Found '+' at position 2
Found '35' at position 3
Found '>' at position 5
Found '5' at position 6
Found '*' at position 7
Found 'y' at position 8
Found ')' at position 9
Found '&&' at position 10
Found '(' at position 12
Found 'z' at position 13
Found '>=' at position 14
Found '3' at position 16
Found '||' at position 18
Found 'k' at position 21
Found '!=' at position 22
Found 'x' at position 24
Found ')' at position 25