Parsica デモ

composer.json

{
    "require": {
        "parsica-php/parsica": "^0.8.1"
    }
}

formula.php

<?php
use Parsica\Parsica\Parser;
use function Parsica\Parsica\{
    between,
    char,
    collect,
    either,
    integer,
    recursive,
};

require(__DIR__."/vendor/autoload.php");


/**
 * 整式を前置記法で表記する
 *
 * @param array|int $ast
 * @return string
 */
function prefix_notation($ast)
{
    if (!is_array($ast)) { return $ast; }

    $operator = $ast["operator"];
    $left = prefix_notation($ast["left"]);
    $right = prefix_notation($ast["right"]);

    return "{$operator} {$left} {$right}";
}

/**
 * 整式を後置記法で表記する
 *
 * @param array|int $ast
 * @return string
 */
function postfix_notation($ast)
{
    if (!is_array($ast)) { return $ast; }

    $operator = $ast["operator"];
    $left = postfix_notation($ast["left"]);
    $right = postfix_notation($ast["right"]);

    return "{$left} {$right} {$operator}";
}


function main()
{
    // 各種のパーサを定義
    // <expression> := <term> [ "+" <expression> ]
    // <term> := <factor> [ "*" <term> ]
    // <factor> := <number> | "(" <expression> ")"

    /** @var Parser<int> */
    $pNumber = integer()->map("intval")->label("number");

    /** @var Parser<array> */
    $pExpression = recursive()->label("expression");

    /** @var Parser<array> */
    $pTerm = recursive()->label("term");

    /** @var Parser<array> */
    $pFactor = recursive()->label("factor");


    $pExpression->recurse(
        either(
            collect($pTerm, char("+"), $pExpression)
                ->map(fn(array $vals) => [
                    "operator" => $vals[1],
                    "left" => $vals[0],
                    "right" => $vals[2],
                ])
            ,
            $pTerm
        )
    );

    $pTerm->recurse(
        either(
            collect($pFactor, char("*"), $pTerm)
                ->map(fn(array $vals) => [
                    "operator" => $vals[1],
                    "left" => $vals[0],
                    "right" => $vals[2],
                ])
            ,
            $pFactor
        )
    );

    $pFactor->recurse(
        either(
            $pNumber,
            between(char("("), char(")"), $pExpression)
        )
    );


    // 中置記法で書いた式
    $infix_notation = "2*(3+4)+5";


    // 抽象構文木 (AST) に変換
    $ast = $pExpression->tryString($infix_notation)->output();
        // => [
        //     "operator" => "+",
        //         "operator" => "*",
        //         "left" => 2,
        //         "right" => [
        //             "operator" => "+",
        //             "left" => 3,
        //             "right" => 4,
        //         ],
        //     ],
        //     "right" => 5,
        // ]


    // 前置記法で出力
    echo prefix_notation($ast) . "\n";  // => "+ * 2 + 3 4 5"

    // 後置記法で出力
    echo postfix_notation($ast) . "\n";  // => "2 3 4 + * 5 +"
}


main();

uri.php

<?php
use function Parsica\Parsica\{
    assemble,
    atLeastOne,
    char,
    everything,
    integer,
    noneOfS,
    optional,
    string,
};

require(__DIR__."/vendor/autoload.php");


// URI を Scheme, Host, Path などに分解する
// parse_url() 相当の処理


// 各パーツのパーサを作っていく

$pScheme = string("http")
    ->append(optional(char("s")))
    ->map(fn($val) => [ "scheme" => $val ]);

$pUserinfo = atLeastOne(noneOfS(":@"))
    ->append(char(":"))
    ->append(atLeastOne(noneOfS("@")))
    ->thenIgnore(char("@"))
    ->map(fn($val) => [ "userinfo" => $val ]);

$pHost = atLeastOne(noneOfS(":/"))
    ->map(fn($val) => [ "host" => $val ]);

$pPort = char(":")->followedBy(integer())
    ->map(fn($val) => [ "port" => $val ]);

$pPath = atLeastOne(noneOfS("?"))
    ->map(fn($val) => [ "path" => $val ]);

$pQuery = char("?")
    ->append(atLeastOne(noneOfS("#")))
    ->map(fn($val) => [ "query" => $val ]);

$pFragment = char("#")
    ->append(everything())
    ->map(fn($val) => [ "fragment" => $val ]);


// 小さなパーサを組み合わせて URI 用のパーサを作る
$pUri = assemble(
    $pScheme,
    string("://")->map(fn($_) => null),
    optional($pUserinfo),
    $pHost,
    optional($pPort),
    optional($pPath),
    optional($pQuery),
    optional($pFragment)
);


var_dump($pUri->tryString("https://example.com/")->output());
    // => [
    //     "scheme" => "https",
    //     "host" => "example.com",
    //     "path" => "/",
    // ]

var_dump($pUri->tryString("https://username:path@example.com:8080/a/b/c/?key=val#target")->output());
    // => [
    //     "scheme" => "https",
    //     "userinfo" => "username:path",
    //     "host" => "example.com",
    //     "port" => "8080",
    //     "path" => "/a/b/c/",
    //     "query" => "?key=val",
    //     "fragment" => "#target",
    // ]

var_dump($pUri->tryString("https//example.com/")->output());
    // => Uncaught Parsica\Parsica\ParserHasFailed: <input>:1:6
    //      |
    //    1 | ...//example.com/
    //      |    ^— column 6
    //    Unexpected <slash>
    //    Expecting '://'