Question

这就是我想要做的事情 - 在Php：给一个字符串，得到这样的结果：

(a()?b|c) a是一个返回false的函数。调用b

c

a()

(a()?(b()?d|e)|c)。同样的原则。最终结果应为d，e或c
(a()?(b()?d|e)|(c()?f|g))。同样的原则。最终结果应为d，e，f或g

我面临的问题是a（在我之前的例子中）也可以是一个表达式，如下所示：

((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))

我试图使用正则表达式来做，但这不起作用。

$res=preg_match_all('/\([^.\(]+\)/', $str, $matches);

所以最后我想像这样调用我的函数：

$final_string=compute("(a(x(y(z()?o|p)))?(b()?d|e)|(c()?f|g))");

$final_string中的最终结果应为d，e，f或g

我很确定之前已经做过一些事情但是无法在谷歌上找到它。你会怎么做？

更准确地说，我想知道如何分析字符串：

$str =
    "
    (myfunction(12684444)
    ?   {* comment *}
        (
            myfunction(1)|
            myfunction(2)|
            myfunction(80)|
            myfunction(120)|
            myfunction(184)|
            myfunction(196)
        ?   {* comment *}
            AAAAA
            {* /comment *}
        |
            {* Ignore all other values: *}
            BBBBB
        ) {* /comment *}

    |   {* comment *}
        CCCC
    )";

Answer 1

我相信你正在寻找类似的东西。在此过程中穿插的解释性评论。

如果您要将语法扩展到远远超出您所拥有的范围（即使您不是这样），请编写一个合适的解析器，而不是尝试在单个正则表达式中执行所有操作。这是一个有趣的练习，展示了PCRE的一些强大功能，但它可以非常轻易成为一个难以维护的混乱。

测试字符串：

$tests = [
    "a",
    "a()",
    "a(b)",
    "(a?b|c)",
    "(a()?(b()?d|e)|(c()?f|g))",
    "((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))",
    "(a(d(f))?b(e(f))|c)"
];

以后再使用。

正则表达式：

$regex = <<<'REGEX'
/
(?(DEFINE)
    # An expression is any function, ternary, or string.
    (?<expression>
        (?&function) | (?&ternary) | (?&string)
    )
)

^(?<expr>

    # A function is a function name (consisting of one or more word characters)
    # followed by an opening parenthesis, an optional parameter (expression),
    # and a closing parenthesis.
    # Optional space is allowed around the parentheses.
    (?<function>
        (?<func_name> \w+ )
        \s*\(\s*
        (?<parameter> (?&expression)? )
        \s*\)\s*
    )

    |

    # A ternary is an opening parenthesis followed by an 'if' expression,
    # a question mark, an expression evaluated when the 'if' is true,
    # a pipe, an expression evaluated when the 'if' is false, and a closing
    # parenthesis.
    # Whitespace is allowed after '('; surrounding '?' and '|'; and before ')'.
    (?<ternary>
        \(\s*
        (?<if> (?&expression) )
        \s*\?\s*
        (?<true> (?&expression) )
        \s*\|\s*
        (?<false> (?&expression) )
        \s*\)
    )

    |

    # A string, for simplicity's sake here, we'll call a sequence of word
    # characters.
    (?<string> \w+ )
)$
/x
REGEX;

自由使用命名捕获组有很大帮助，x（PCRE_EXTENDED）修饰符允许使用注释和空格。 (?(DEFINE)...)块允许您定义子模式以供仅供参考。

正则表达式演示：

foreach ($tests as $test) {
    if (preg_match($regex, $test, $m)) {
        echo "expression: $m[expr]\n";

        if ($m['function']) {
            echo "function: $m[function]\n",
                 "function name: $m[func_name]\n",
                 "parameter: $m[parameter]\n";
        } elseif ($m['ternary']) {
            echo "ternary: $m[ternary]\n",
                 "if: $m[if]\n",
                 "true: $m[true]\n",
                 "false: $m[false]\n";
        } else {
            echo "string: $m[string]\n";
        }

        echo "\n";
    }
}

输出：

expression: a
string: a

expression: a()
function: a()
function name: a
parameter: 

expression: a(b)
function: a(b)
function name: a
parameter: b

expression: (a?b|c)
ternary: (a?b|c)
if: a
true: b
false: c

expression: (a()?(b()?d|e)|(c()?f|g))
ternary: (a()?(b()?d|e)|(c()?f|g))
if: a()
true: (b()?d|e)
false: (c()?f|g)

expression: ((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))
ternary: ((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))
if: (h() ? a | i)
true: (b() ? d | e)
false: (c() ? f | g)

expression: (a(d(f))?b(e(f))|c)
ternary: (a(d(f))?b(e(f))|c)
if: a(d(f))
true: b(e(f))
false: c

有点冗长，但很好地展示了什么是匹配的。

示例`compute()`功能：

function compute($expr) {
    $regex = '/.../x'; // regex from above
    if (!preg_match($regex, $expr, $m)) {
        return false;
    }

    if ($m['function']) {
        if ($m['parameter']) {
            return $m['func_name'](compute($m['parameter']));
        } else {
            return $m['func_name']();
        }
    }

    if ($m['ternary']) {
        return compute($m['if']) ? compute($m['true']) : compute($m['false']);
    }

    return $m['string'];
}

非常简单 - 执行匹配的函数，评估匹配的三元表达式，或返回匹配的字符串;适当时递归。

`compute()`演示：

function a() {return true;}
function b() {return false;}
function d() {return true;}
function e() {return false;}
function h() {return true;}

foreach ($tests as $test) {
    $result = compute($test);
    echo "$test returns: ";
    var_dump($result);
}

输出：

a returns: string(1) "a"
a() returns: bool(true)
a(b) returns: bool(true)
(a?b|c) returns: string(1) "b"
(a()?(b()?d|e)|(c()?f|g)) returns: string(1) "e"
((h() ? a | i) ? (b() ? d | e) | (c() ? f | g)) returns: string(1) "e"
(a(d(f))?b(e(f))|c) returns: bool(false)

我很确定这是正确的。

Answer 2

在这里扩展@PaulCrovella正则表达式这将允许任何级别关闭任何表达式周围的嵌套括号并进行解析并相应地修剪。空白也被修剪。

PHP示例：

 $rx = 
 '/
      ^ 
      (?<found>                     # (1 start)
           \h* 
           (?:

                # A function is a function name (consisting of one or more word characters)
                # followed by an opening parenthesis, an optional parameter (expression),
                # and a closing parenthesis.

                (?<function>                  # (2 start)
                     (?>
                          (?<func_name> \w+ )           # (3)
                          \h* \(   
                          (?<parameter>                 # (4 start)
                               (?&expression) 
                            |  
                          )                             # (4 end)
                          \h* \)  
                     )
                )                             # (2 end)

             |  

                # A ternary is an opening \'if\' expression,
                # a question mark, an expression evaluated when the \'if\' is true,
                # a pipe, an expression evaluated when the \'if\' is false.

                (?<pt> \( )?                  # (5)
                (?<ternary>                   # (6 start)
                     (?>
                          (?<if>                        # (7 start)
                               (?&expression)  
                          )                             # (7 end)
                          \h* \? \h*              
                          (?<true>                      # (8 start)
                               (?&expression)  
                          )                             # (8 end)
                          \h* \| \h*        
                          (?<false>                     # (9 start)
                               (?&expression)  
                          )                             # (9 end)
                     )
                )                             # (6 end)
                (?(\'pt\') \h* \) )

             |  

                # A string, for simplicity\'s sake here, we\'ll call a sequence of word
                # characters.

                (?<string>                    # (10 start)
                     (?> \w+ )
                )                             # (10 end)
             |  
                (?<parens>                    # (11 start)
                     (?>
                          \( \h* 
                          (?<parens_core>               # (12 start)
                               \h* 
                               (?&p_expression) 
                          )                             # (12 end)
                          \h* \)
                     )
                )                             # (11 end)
           )
      )                             # (1 end)
      \h* 
      $ 

      (?(DEFINE)
           # expression is any function, parenthesized-ternary, or string.
           (?<expression>                # (13 start)
                \h* 
                (?:
                     (?&function)  
                  |  \( (?&ternary) \h* \) 
                  |  (?&string) 
                  |  (?&parens)  
                )
           )                             # (13 end)

           # p_expression is any parenthesized - function, ternary, or string.
           (?<p_expression>              # (14 start)
                \h* 
                (?:
                     (?&function)  
                  |  (?= . )
                     (?&ternary) 
                  |  (?&string) 
                  |  (?&parens)  
                )
           )                             # (14 end)
      )

 /x';


 function compute($expr) {
     global $rx;
     if (!preg_match($rx, $expr, $m)) {
         return false;
     }

     if ($m['function']) {
         if ($m['parameter']) {
             return $m['func_name'](compute($m['parameter']));
         } else {
             return $m['func_name']( '' );
         }
     }

     if ($m['ternary']) {
         return compute($m['if']) ? compute($m['true']) : compute($m['false']);
     }

     if ($m['parens']) {
         return compute($m['parens_core']);
     }

     return $m['string'];
 }

 function a() {return true; }
 function b() {return false;}
 function d() {return true;}
 function e() {return false;}
 function h() {return true;}
 function intro($p) {if ($p) return 'intro'; return false;}
 function type($p) {if ($p) return 'type'; return false;}
 function insist($p) {if ($p) return 'insist'; return false;}


 $tests = array(
     "a",
     "a()",
     "a(b)",
     "(a?b|c)",
     "(a()?(b()?d|e)|(c()?f|g))",
     "((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))",
     "(a(d(f))?b(e(f))|c)",
     "------------",
     "a?b|c",
     "(a?b|c)",
     " ( ( ( ( ( a ) ) ? ( ( b ) ) | ( ( c ) ) ) ) ) ",
     "b( (oo ? p |u) ) ? x | y",
     "a ?b() | c",
     " a? ( b ? t | r)  | d  ",
     "a()",
     "a? (bhh )   |(c)",
     "(a) ? ((b(oo) ? x | y )) | (c)",
     "a(((b)))",
     "a?    (bhh )   |((c))",
     "(a()?(b()?d|e)|(c()?f|g))",
     "((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))",
     "(((h() ? a | i) ? (b() ? d | e) | (c() ? f | g)))",
     "((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))",
     "(a(d(f))?b(e(f))|c)",
     "------------",
     "((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))",
     "(a(d(f))?b(e(f))|c)",
     '(intro(intro(type(insist(poou))))?toutou|tutu)',
     'type()intro(intro(type(insist(poou))))?type()|tutu'

 );


 foreach ($tests as $test) {
     $result = compute($test);
     echo "$test returns: ";
     var_dump($result);
 }

输出：

a() returns: bool(true)
a(b) returns: bool(true)
(a?b|c) returns: string(1) "b"
(a()?(b()?d|e)|(c()?f|g)) returns: string(1) "e"
((h() ? a | i) ? (b() ? d | e) | (c() ? f | g)) returns: string(1) "e"
(a(d(f))?b(e(f))|c) returns: bool(false)
------------ returns: bool(false)
a?b|c returns: string(1) "b"
(a?b|c) returns: string(1) "b"
( ( ( ( ( a ) ) ? ( ( b ) ) | ( ( c ) ) ) ) )  returns: string(1) "b"
b( (oo ? p |u) ) ? x | y returns: string(1) "y"
a ?b() | c returns: bool(false)
a? ( b ? t | r)  | d  returns: string(1) "t"
a() returns: bool(true)
a? (bhh )  |(c) returns: string(3) "bhh"
(a) ? ((b(oo) ? x | y )) | (c) returns: bool(false)
a(((b))) returns: bool(true)
a?    (bhh )  |((c)) returns: string(3) "bhh"
(a()?(b()?d|e)|(c()?f|g)) returns: string(1) "e"
((h() ? a | i) ? (b() ? d | e) | (c() ? f | g)) returns: string(1) "e"
(((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))) returns: string(1) "e"
((h() ? a | i) ? (b() ? d | e) | (c() ? f | g)) returns: string(1) "e"
(a(d(f))?b(e(f))|c) returns: bool(false)
------------ returns: bool(false)
((h() ? a | i) ? (b() ? d | e) | (c() ? f | g)) returns: string(1) "e"
(a(d(f))?b(e(f))|c) returns: bool(false)
(intro(intro(type(insist(poou))))?toutou|tutu) returns: string(6) "toutou"
type()intro(intro(type(insist(poou))))?type()|tutu returns: bool(false)

Answer 3

这是我的基本＆＃34;工作和完成工作的版本。它的一半＆＃34;递归（一个可以调用函数的循环）和我计划做的改进（处理＆＃34; +＆＃34;分隔符到＆＃34;添加＆＃34;返回两个函数，以及句柄＆＃34; =＆＃34;设置变量以使返回函数的值的短别名）似乎很容易在_compute()函数中实现...也许因为我自己写了代码，也许是因为像Paul Crovella说的那样，我没有使用PCRE，因为它很容易变成一个难以维护的混乱...

注意：这段代码可以很容易地进行优化，并且它并不完美（有些情况下它不像(a()+b())那样工作）...但是如果有人愿意完成它他/她＆＃ 39;欢迎！

class Parser
{
    private $ref = array(
        'a'         => array( 'type' => 'fn',  'val' => '_a'),
        'b'         => array( 'type' => 'fn',  'val' => '_b'),
        'c'         => array( 'type' => 'fn',  'val' => '_c'),
        'd'         => array( 'type' => 'fn',  'val' => '_d'),
        'e'         => array( 'type' => 'fn',  'val' => '_e'),
        'f'         => array( 'type' => 'fn',  'val' => '_f'),
        'intro'         => array( 'type' => 'fn',  'val' => '_getIntro'),
        'insist'        => array( 'type' => 'fn',  'val' => '_insist'),
        'summoner_name' => array( 'type' => 'fn',  'val' => '_getSummonerName'),
        'type'          => array( 'type' => 'fn',  'val' => '_getEtat'),
        ' '             => array( 'type' => 'str', 'val' => ' ')
    );
    private function _a($p)        { return 'valfnA'; }
    private function _b($p)        { return 'valfnB'; }
    private function _c($p)        { return 'valfnC'; }
    private function _d($p)        { return 'valfnD'; }
    private function _e($p)        { return 'valfnE'; }
    private function _f($p)        { return 'valfnF'; }
    private function _getIntro($p)        { return 'valGetIntro'; }
    private function _insist($p)          { return 'valInsist'; }
    private function _getSummonerName($p) { return 'valGetSqmmonerName'; }
    private function _getEtat($p)         { return 'valGetEtat'; }

    private function _convertKey($key, $params=false)
    {
        $retour = 'indéfini';
        if (isset($this->ref[$key])) {
            $val = $this->ref[$key];
            switch ($val['type']) {
                case 'fn':
                    $val=$val['val'];
                    if (method_exists($this, $val)) {
                        $retour = $this->$val($params);
                    }
                    break;

                default:
                    if (isset($this->val['val'])) {
                        $retour = $this->val['val'];
                    }
                    break;
            }
        }
        return $retour;
    }
    private function _compute($str)
    {
        $p=strpos($str, '?');
        if ($p===false) {
            $p=strpos($str, '=');
            if ($p===false) {
                return $str;
            }
        } else {
            $or=strpos($str, '|');
            if ($or===false) {
                return false;
            }
            $s=substr($str,0,$p);
            if (empty($s) || (strtolower($s)=='false')) {
                return substr($str, $or+1);
            }
            return substr($str, $p+1, ($or-$p)-1);
        }
        return $str;
    }
    private function _getTexte($str, $i, $level)
    {
        if (empty($str)) {
            return $str;
        }
        $level++;
        $f   = (strlen($str)-$i);
        $val = substr($str, $i);
        do {
            $d = $i;
            do {
                $p=$d;
                $d=strpos($str, '(', $p+1);
                if (($p==$i) && ($d===false)) {
                    $retour = $this->_compute($str);
                    return $retour;
                } elseif (($d===false) && ($p>$i)) {
                    $f=strpos($str, ')', $p+1);
                    if ($f===false) {
                        return false;
                    }
                    $d=$p;
                    while((--$d)>=$i) {
                        if (($str[$d]!=' ')
                            && ($str[$d]!='_')
                            && (!ctype_alnum($str[$d]))
                        ) {
                            break;
                        }
                    }
                    if ($d>=$i) {
                        $d++;
                    } else {
                        $d=$i;
                    }
                    $val=substr($str, $d, ($f-$d)+1);
                    $fn=substr($str, $d, $p-$d);
                    $param=$this->_getTexte(
                        substr($str, $p+1, ($f-$p)-1), 0, $level+1
                    );
                    if (!empty($fn)) {
                        $val = $this->_convertKey($fn, $param);
                    } else {
                        $val = $this->_compute($param);
                    }
                    $str = substr($str, 0, $d).$val.substr($str, $f+1);
                    break;
                } elseif ($d===false) {
                    break;
                }
            } while (true);
        } while (true);
    }
    public function parse($str)
    {
        $retour=preg_replace('/{\*[^.{]+\*}/', '', $str); //}
        $retour=str_replace("\n", "", $retour);
        $retour=str_replace("\r", "", $retour);
        while (strpos($retour, '  ')!==false) {
            $retour=str_replace("  ", " ", $retour);
        }
        return trim($this->_getTexte($retour, 0, 0));
    }
}

$p=new Parser();
$tests = [
    "a",
    "a()",
    "a(b)",
    "(a?b|c)",
    "(a()?(b()?d|e)|(c()?f|g))",
    "(a()?(b()?d|e)|(c()?f()|g))",
    "((h() ? a | i) ? (b() ? d | e) | (c() ? f | g))",
    "(a(d(f))?b(e(f))|c)",
    '(intro(intro(type(insist(poou))))?toutou|tutu)',
    'type()intro(intro(type(insist(poou))))?type()|tutu'
];
foreach ($tests as $test) {
    $res=$p->parse($test);
    echo $test.' = '.var_export($res,true)."\n";
}

编写一个简单的语法分析器

3 个答案:

测试字符串：

正则表达式：

正则表达式演示：

输出：

示例`compute()`功能：

`compute()`演示：

输出：

编写一个简单的语法分析器

3 个答案:

测试字符串：

正则表达式：

正则表达式演示：

输出：

示例compute()功能：

compute()演示：

输出：

示例`compute()`功能：

`compute()`演示：