ExprParser.php

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<?php
use UtfNormal\Validator;
 
// Character classes
define( 'EXPR_WHITE_CLASS', " \t\r\n" );
define( 'EXPR_NUMBER_CLASS', '0123456789.' );
 
// Token types
define( 'EXPR_WHITE', 1 );
define( 'EXPR_NUMBER', 2 );
define( 'EXPR_NEGATIVE', 3 );
define( 'EXPR_POSITIVE', 4 );
define( 'EXPR_PLUS', 5 );
define( 'EXPR_MINUS', 6 );
define( 'EXPR_TIMES', 7 );
define( 'EXPR_DIVIDE', 8 );
define( 'EXPR_MOD', 9 );
define( 'EXPR_OPEN', 10 );
define( 'EXPR_CLOSE', 11 );
define( 'EXPR_AND', 12 );
define( 'EXPR_OR', 13 );
define( 'EXPR_NOT', 14 );
define( 'EXPR_EQUALITY', 15 );
define( 'EXPR_LESS', 16 );
define( 'EXPR_GREATER', 17 );
define( 'EXPR_LESSEQ', 18 );
define( 'EXPR_GREATEREQ', 19 );
define( 'EXPR_NOTEQ', 20 );
define( 'EXPR_ROUND', 21 );
define( 'EXPR_EXPONENT', 22 );
define( 'EXPR_SINE', 23 );
define( 'EXPR_COSINE', 24 );
define( 'EXPR_TANGENS', 25 );
define( 'EXPR_ARCSINE', 26 );
define( 'EXPR_ARCCOS', 27 );
define( 'EXPR_ARCTAN', 28 );
define( 'EXPR_EXP', 29 );
define( 'EXPR_LN', 30 );
define( 'EXPR_ABS', 31 );
define( 'EXPR_FLOOR', 32 );
define( 'EXPR_TRUNC', 33 );
define( 'EXPR_CEIL', 34 );
define( 'EXPR_POW', 35 );
define( 'EXPR_PI', 36 );
define( 'EXPR_FMOD', 37 );
define( 'EXPR_SQRT', 38 );
 
class ExprParser {
    public $maxStackSize = 100;
 
    public $precedence = [
        EXPR_NEGATIVE => 10,
        EXPR_POSITIVE => 10,
        EXPR_EXPONENT => 10,
        EXPR_SINE => 9,
        EXPR_COSINE => 9,
        EXPR_TANGENS => 9,
        EXPR_ARCSINE => 9,
        EXPR_ARCCOS => 9,
        EXPR_ARCTAN => 9,
        EXPR_EXP => 9,
        EXPR_LN => 9,
        EXPR_ABS => 9,
        EXPR_FLOOR => 9,
        EXPR_TRUNC => 9,
        EXPR_CEIL => 9,
        EXPR_NOT => 9,
        EXPR_SQRT => 9,
        EXPR_POW => 8,
        EXPR_TIMES => 7,
        EXPR_DIVIDE => 7,
        EXPR_MOD => 7,
        EXPR_FMOD => 7,
        EXPR_PLUS => 6,
        EXPR_MINUS => 6,
        EXPR_ROUND => 5,
        EXPR_EQUALITY => 4,
        EXPR_LESS => 4,
        EXPR_GREATER => 4,
        EXPR_LESSEQ => 4,
        EXPR_GREATEREQ => 4,
        EXPR_NOTEQ => 4,
        EXPR_AND => 3,
        EXPR_OR => 2,
        EXPR_PI => 0,
        EXPR_OPEN => -1,
        EXPR_CLOSE => -1,
    ];
 
    public $names = [
        EXPR_NEGATIVE => '-',
        EXPR_POSITIVE => '+',
        EXPR_NOT => 'not',
        EXPR_TIMES => '*',
        EXPR_DIVIDE => '/',
        EXPR_MOD => 'mod',
        EXPR_FMOD => 'fmod',
        EXPR_PLUS => '+',
        EXPR_MINUS => '-',
        EXPR_ROUND => 'round',
        EXPR_EQUALITY => '=',
        EXPR_LESS => '<',
        EXPR_GREATER => '>',
        EXPR_LESSEQ => '<=',
        EXPR_GREATEREQ => '>=',
        EXPR_NOTEQ => '<>',
        EXPR_AND => 'and',
        EXPR_OR => 'or',
        EXPR_EXPONENT => 'e',
        EXPR_SINE => 'sin',
        EXPR_COSINE => 'cos',
        EXPR_TANGENS => 'tan',
        EXPR_ARCSINE => 'asin',
        EXPR_ARCCOS => 'acos',
        EXPR_ARCTAN => 'atan',
        EXPR_LN => 'ln',
        EXPR_EXP => 'exp',
        EXPR_ABS => 'abs',
        EXPR_FLOOR => 'floor',
        EXPR_TRUNC => 'trunc',
        EXPR_CEIL => 'ceil',
        EXPR_POW => '^',
        EXPR_PI => 'pi',
        EXPR_SQRT => 'sqrt',
    ];
 
    public $words = [
        'mod' => EXPR_MOD,
        'fmod' => EXPR_FMOD,
        'and' => EXPR_AND,
        'or' => EXPR_OR,
        'not' => EXPR_NOT,
        'round' => EXPR_ROUND,
        'div' => EXPR_DIVIDE,
        'e' => EXPR_EXPONENT,
        'sin' => EXPR_SINE,
        'cos' => EXPR_COSINE,
        'tan' => EXPR_TANGENS,
        'asin' => EXPR_ARCSINE,
        'acos' => EXPR_ARCCOS,
        'atan' => EXPR_ARCTAN,
        'exp' => EXPR_EXP,
        'ln' => EXPR_LN,
        'abs' => EXPR_ABS,
        'trunc' => EXPR_TRUNC,
        'floor' => EXPR_FLOOR,
        'ceil' => EXPR_CEIL,
        'pi' => EXPR_PI,
        'sqrt' => EXPR_SQRT,
    ];
 
    public function doExpression( $expr ) {
        $operands = [];
        $operators = [];
 
        # Unescape inequality operators
        $expr = strtr( $expr, [ '&lt;' => '<', '&gt;' => '>',
            '&minus;' => '-', '−' => '-' ] );
 
        $p = 0;
        $end = strlen( $expr );
        $expecting = 'expression';
        $name = '';
 
        while ( $p < $end ) {
            if ( count( $operands ) > $this->maxStackSize || count( $operators ) > $this->maxStackSize ) {
                throw new ExprError( 'stack_exhausted' );
            }
            $char = $expr[$p];
            $char2 = substr( $expr, $p, 2 );
 
            // Mega if-elseif-else construct
            // Only binary operators fall through for processing at the bottom, the rest
            // finish their processing and continue
 
            // First the unlimited length classes
 
            if ( false !== strpos( EXPR_WHITE_CLASS, $char ) ) {
                // Whitespace
                $p += strspn( $expr, EXPR_WHITE_CLASS, $p );
                continue;
            } elseif ( false !== strpos( EXPR_NUMBER_CLASS, $char ) ) {
                // Number
                if ( $expecting !== 'expression' ) {
                    throw new ExprError( 'unexpected_number' );
                }
 
                // Find the rest of it
                $length = strspn( $expr, EXPR_NUMBER_CLASS, $p );
                // Convert it to float, silently removing double decimal points
                $operands[] = (float)substr( $expr, $p, $length );
                $p += $length;
                $expecting = 'operator';
                continue;
            } elseif ( ctype_alpha( $char ) ) {
                // Word
                // Find the rest of it
                $remaining = substr( $expr, $p );
                if ( !preg_match( '/^[A-Za-z]*/', $remaining, $matches ) ) {
                    // This should be unreachable
                    throw new ExprError( 'preg_match_failure' );
                }
                $word = strtolower( $matches[0] );
                $p += strlen( $word );
 
                // Interpret the word
                if ( !isset( $this->words[$word] ) ) {
                    throw new ExprError( 'unrecognised_word', $word );
                }
                $op = $this->words[$word];
                switch ( $op ) {
                    // constant
                    case EXPR_EXPONENT:
                        if ( $expecting !== 'expression' ) {
                            break;
                        }
                        $operands[] = exp( 1 );
                        $expecting = 'operator';
                        continue 2;
                    case EXPR_PI:
                        if ( $expecting !== 'expression' ) {
                            throw new ExprError( 'unexpected_number' );
                        }
                        $operands[] = pi();
                        $expecting = 'operator';
                        continue 2;
                    // Unary operator
                    case EXPR_NOT:
                    case EXPR_SINE:
                    case EXPR_COSINE:
                    case EXPR_TANGENS:
                    case EXPR_ARCSINE:
                    case EXPR_ARCCOS:
                    case EXPR_ARCTAN:
                    case EXPR_EXP:
                    case EXPR_LN:
                    case EXPR_ABS:
                    case EXPR_FLOOR:
                    case EXPR_TRUNC:
                    case EXPR_CEIL:
                    case EXPR_SQRT:
                        if ( $expecting !== 'expression' ) {
                            throw new ExprError( 'unexpected_operator', $word );
                        }
                        $operators[] = $op;
                        continue 2;
                }
                // Binary operator, fall through
                $name = $word;
            } elseif ( $char2 === '<=' ) {
                $name = $char2;
                $op = EXPR_LESSEQ;
                $p += 2;
            } elseif ( $char2 === '>=' ) {
                $name = $char2;
                $op = EXPR_GREATEREQ;
                $p += 2;
            } elseif ( $char2 === '<>' || $char2 === '!=' ) {
                $name = $char2;
                $op = EXPR_NOTEQ;
                $p += 2;
            } elseif ( $char === '+' ) {
                ++$p;
                if ( $expecting === 'expression' ) {
                    // Unary plus
                    $operators[] = EXPR_POSITIVE;
                    continue;
                } else {
                    // Binary plus
                    $op = EXPR_PLUS;
                }
            } elseif ( $char === '-' ) {
                ++$p;
                if ( $expecting === 'expression' ) {
                    // Unary minus
                    $operators[] = EXPR_NEGATIVE;
                    continue;
                } else {
                    // Binary minus
                    $op = EXPR_MINUS;
                }
            } elseif ( $char === '*' ) {
                $name = $char;
                $op = EXPR_TIMES;
                ++$p;
            } elseif ( $char === '/' ) {
                $name = $char;
                $op = EXPR_DIVIDE;
                ++$p;
            } elseif ( $char === '^' ) {
                $name = $char;
                $op = EXPR_POW;
                ++$p;
            } elseif ( $char === '(' ) {
                if ( $expecting === 'operator' ) {
                    throw new ExprError( 'unexpected_operator', '(' );
                }
                $operators[] = EXPR_OPEN;
                ++$p;
                continue;
            } elseif ( $char === ')' ) {
                $lastOp = end( $operators );
                while ( $lastOp && $lastOp != EXPR_OPEN ) {
                    $this->doOperation( $lastOp, $operands );
                    array_pop( $operators );
                    $lastOp = end( $operators );
                }
                if ( $lastOp ) {
                    array_pop( $operators );
                } else {
                    throw new ExprError( 'unexpected_closing_bracket' );
                }
                $expecting = 'operator';
                ++$p;
                continue;
            } elseif ( $char === '=' ) {
                $name = $char;
                $op = EXPR_EQUALITY;
                ++$p;
            } elseif ( $char === '<' ) {
                $name = $char;
                $op = EXPR_LESS;
                ++$p;
            } elseif ( $char === '>' ) {
                $name = $char;
                $op = EXPR_GREATER;
                ++$p;
            } else {
                $utfExpr = Validator::cleanUp( substr( $expr, $p ) );
                throw new ExprError( 'unrecognised_punctuation', mb_substr( $utfExpr, 0, 1 ) );
            }
 
            // Binary operator processing
            if ( $expecting === 'expression' ) {
                throw new ExprError( 'unexpected_operator', $name );
            }
 
            // Shunting yard magic
            $lastOp = end( $operators );
            while ( $lastOp && $this->precedence[$op] <= $this->precedence[$lastOp] ) {
                $this->doOperation( $lastOp, $operands );
                array_pop( $operators );
                $lastOp = end( $operators );
            }
            $operators[] = $op;
            $expecting = 'expression';
        }
 
        // Finish off the operator array
        // @codingStandardsIgnoreStart
        while ( $op = array_pop( $operators ) ) {
        // @codingStandardsIgnoreEnd
            if ( $op == EXPR_OPEN ) {
                throw new ExprError( 'unclosed_bracket' );
            }
            $this->doOperation( $op, $operands );
        }
 
        return implode( "<br />\n", $operands );
    }
 
    public function doOperation( $op, &$stack ) {
        switch ( $op ) {
            case EXPR_NEGATIVE:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = -$arg;
                break;
            case EXPR_POSITIVE:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                break;
            case EXPR_TIMES:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = $left * $right;
                    break;
            case EXPR_DIVIDE:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                if ( !$right ) {
                    throw new ExprError( 'division_by_zero', $this->names[$op] );
                }
                $stack[] = $left / $right;
                break;
            case EXPR_MOD:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = (int)array_pop( $stack );
                $left = (int)array_pop( $stack );
                if ( !$right ) {
                    throw new ExprError( 'division_by_zero', $this->names[$op] );
                }
                $stack[] = $left % $right;
                break;
            case EXPR_FMOD:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = (double)array_pop( $stack );
                $left = (double)array_pop( $stack );
                if ( !$right ) {
                    throw new ExprError( 'division_by_zero', $this->names[$op] );
                }
                $stack[] = fmod( $left, $right );
                break;
            case EXPR_PLUS:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = $left + $right;
                break;
            case EXPR_MINUS:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = $left - $right;
                break;
            case EXPR_AND:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left && $right ) ? 1 : 0;
                break;
            case EXPR_OR:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left || $right ) ? 1 : 0;
                break;
            case EXPR_EQUALITY:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left == $right ) ? 1 : 0;
                break;
            case EXPR_NOT:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = ( !$arg ) ? 1 : 0;
                break;
            case EXPR_ROUND:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $digits = (int)array_pop( $stack );
                $value = array_pop( $stack );
                $stack[] = round( $value, $digits );
                break;
            case EXPR_LESS:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left < $right ) ? 1 : 0;
                break;
            case EXPR_GREATER:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left > $right ) ? 1 : 0;
                break;
            case EXPR_LESSEQ:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left <= $right ) ? 1 : 0;
                break;
            case EXPR_GREATEREQ:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left >= $right ) ? 1 : 0;
                break;
            case EXPR_NOTEQ:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = ( $left != $right ) ? 1 : 0;
                break;
            case EXPR_EXPONENT:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $stack[] = $left * pow( 10, $right );
                break;
            case EXPR_SINE:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = sin( $arg );
                break;
            case EXPR_COSINE:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = cos( $arg );
                break;
            case EXPR_TANGENS:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = tan( $arg );
                break;
            case EXPR_ARCSINE:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                if ( $arg < -1 || $arg > 1 ) {
                    throw new ExprError( 'invalid_argument', $this->names[$op] );
                }
                $stack[] = asin( $arg );
                break;
            case EXPR_ARCCOS:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                if ( $arg < -1 || $arg > 1 ) {
                    throw new ExprError( 'invalid_argument', $this->names[$op] );
                }
                $stack[] = acos( $arg );
                break;
            case EXPR_ARCTAN:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = atan( $arg );
                break;
            case EXPR_EXP:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = exp( $arg );
                break;
            case EXPR_LN:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                if ( $arg <= 0 ) {
                    throw new ExprError( 'invalid_argument_ln', $this->names[$op] );
                }
                $stack[] = log( $arg );
                break;
            case EXPR_ABS:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = abs( $arg );
                break;
            case EXPR_FLOOR:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = floor( $arg );
                break;
            case EXPR_TRUNC:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = (int)$arg;
                break;
            case EXPR_CEIL:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $stack[] = ceil( $arg );
                break;
            case EXPR_POW:
                if ( count( $stack ) < 2 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $right = array_pop( $stack );
                $left = array_pop( $stack );
                $result = pow( $left, $right );
                if ( $result === false ) {
                    throw new ExprError( 'division_by_zero', $this->names[$op] );
                }
                $stack[] = $result;
                break;
            case EXPR_SQRT:
                if ( count( $stack ) < 1 ) {
                    throw new ExprError( 'missing_operand', $this->names[$op] );
                }
                $arg = array_pop( $stack );
                $result = sqrt( $arg );
                if ( is_nan( $result ) ) {
                    throw new ExprError( 'not_a_number', $this->names[$op] );
                }
                $stack[] = $result;
                break;
            default:
                // Should be impossible to reach here.
                throw new ExprError( 'unknown_error' );
        }
    }
}