WC_Eval_Math
Class WC_Eval_Math.
Defined (1)
The class is defined in the following location(s).
- /includes/libraries/class-wc-eval-math.php
- class WC_Eval_Math {
- /**
- * Last error.
- *
- * @var string
- */
- public static $last_error = null;
- /**
- * Variables (and constants).
- *
- * @var array
- */
- public static $v = array( 'e' => 2.71, 'pi' => 3.14 );
- /**
- * User-defined functions.
- *
- * @var array
- */
- public static $f = array();
- /**
- * Constants.
- *
- * @var array
- */
- public static $vb = array( 'e', 'pi' );
- /**
- * Built-in functions.
- *
- * @var array
- */
- public static $fb = array();
- /**
- * Evaluate maths string.
- *
- * @param string $expr
- * @return mixed
- */
- public static function evaluate( $expr ) {
- self::$last_error = null;
- $expr = trim( $expr );
- if ( substr( $expr, -1, 1 ) == ';' ) $expr = substr( $expr, 0, strlen( $expr ) -1 ); // strip semicolons at the end
- // ===============
- // is it a variable assignment?
- if ( preg_match( '/^\s*([a-z]\w*)\s*=\s*(.+)$/', $expr, $matches ) ) {
- if ( in_array( $matches[1], self::$vb ) ) { // make sure we're not assigning to a constant
- return self::trigger( "cannot assign to constant '$matches[1]'" );
- }
- if ( ( $tmp = self::pfx( self::nfx( $matches[2] ) ) ) === false ) return false; // get the result and make sure it's good
- self::$v[ $matches[1] ] = $tmp; // if so, stick it in the variable array
- return self::$v[ $matches[1] ]; // and return the resulting value
- // ===============
- // is it a function assignment?
- } elseif ( preg_match( '/^\s*([a-z]\w*)\s*\(\s*([a-z]\w*(?:\s*, \s*[a-z]\w*)*)\s*\)\s*=\s*(.+)$/', $expr, $matches ) ) {
- $fnn = $matches[1]; // get the function name
- if ( in_array( $matches[1], self::$fb ) ) { // make sure it isn't built in
- return self::trigger( "cannot redefine built-in function '$matches[1]()'" );
- }
- $args = explode( ", ", preg_replace( "/\s+/", "", $matches[2] ) ); // get the arguments
- if ( ( $stack = self::nfx( $matches[3] ) ) === false ) return false; // see if it can be converted to postfix
- $stack_size = count( $stack );
- for ( $i = 0; $i < $stack_size; $i++ ) { // freeze the state of the non-argument variables
- $token = $stack[ $i ];
- if ( preg_match( '/^[a-z]\w*$/', $token ) and ! in_array( $token, $args ) ) {
- if ( array_key_exists( $token, self::$v ) ) {
- $stack[ $i ] = self::$v[ $token ];
- } else {
- return self::trigger( "undefined variable '$token' in function definition" );
- }
- }
- }
- self::$f[ $fnn ] = array( 'args' => $args, 'func' => $stack );
- return true;
- // ===============
- } else {
- return self::pfx( self::nfx( $expr ) ); // straight up evaluation, woo
- }
- }
- /**
- * Convert infix to postfix notation.
- *
- * @param string $expr
- * @return string
- */
- private static function nfx( $expr ) {
- $index = 0;
- $stack = new WC_Eval_Math_Stack;
- $output = array(); // postfix form of expression, to be passed to pfx()
- $expr = trim( $expr );
- $ops = array( '+', '-', '*', '/', '^', '_' );
- $ops_r = array( '+' => 0, '-' => 0, '*' => 0, '/' => 0, '^' => 1 ); // right-associative operator?
- $ops_p = array( '+' => 0, '-' => 0, '*' => 1, '/' => 1, '_' => 1, '^' => 2 ); // operator precedence
- $expecting_op = false; // we use this in syntax-checking the expression
- // and determining when a - is a negation
- if ( preg_match( "/[^\w\s+*^\/()\., -]/", $expr, $matches ) ) { // make sure the characters are all good
- return self::trigger( "illegal character '{$matches[0]}'" );
- }
- while ( 1 ) { // 1 Infinite Loop ;)
- $op = substr( $expr, $index, 1 ); // get the first character at the current index
- // find out if we're currently at the beginning of a number/variable/function/parenthesis/operand
- $ex = preg_match( '/^([A-Za-z]\w*\(?|\d+(?:\.\d*)?|\.\d+|\()/', substr( $expr, $index ), $match );
- // ===============
- if ( '-' === $op and ! $expecting_op ) { // is it a negation instead of a minus?
- $stack->push( '_' ); // put a negation on the stack
- $index++;
- } elseif ( '_' === $op ) { // we have to explicitly deny this, because it's legal on the stack
- return self::trigger( "illegal character '_'" ); // but not in the input expression
- // ===============
- } elseif ( ( in_array( $op, $ops ) or $ex ) and $expecting_op ) { // are we putting an operator on the stack?
- if ( $ex ) { // are we expecting an operator but have a number/variable/function/opening parethesis?
- $op = '*';
- $index--; // it's an implicit multiplication
- }
- // heart of the algorithm:
- while ( $stack->count > 0 and ( $o2 = $stack->last() ) and in_array( $o2, $ops ) and ( $ops_r[ $op ] ? $ops_p[ $op ] < $ops_p[ $o2 ] : $ops_p[ $op ] <= $ops_p[ $o2 ] ) ) {
- $output[] = $stack->pop(); // pop stuff off the stack into the output
- }
- // many thanks: https://en.wikipedia.org/wiki/Reverse_Polish_notation#The_algorithm_in_detail
- $stack->push( $op ); // finally put OUR operator onto the stack
- $index++;
- $expecting_op = false;
- // ===============
- } elseif ( ')' === $op && $expecting_op ) { // ready to close a parenthesis?
- while ( ( $o2 = $stack->pop() ) != '(' ) { // pop off the stack back to the last (
- if ( is_null( $o2 ) ) {
- return self::trigger( "unexpected ')'" );
- } else {
- $output[] = $o2;
- }
- }
- if ( preg_match( "/^([A-Za-z]\w*)\($/", $stack->last( 2 ), $matches ) ) { // did we just close a function?
- $fnn = $matches[1]; // get the function name
- $arg_count = $stack->pop(); // see how many arguments there were (cleverly stored on the stack, thank you)
- $output[] = $stack->pop(); // pop the function and push onto the output
- if ( in_array( $fnn, self::$fb ) ) { // check the argument count
- if ( $arg_count > 1 )
- return self::trigger( "too many arguments ($arg_count given, 1 expected)" );
- } elseif ( array_key_exists( $fnn, self::$f ) ) {
- if ( count( self::$f[ $fnn ]['args'] ) != $arg_count )
- return self::trigger( "wrong number of arguments ($arg_count given, " . count( self::$f[ $fnn ]['args'] ) . " expected)" );
- } else { // did we somehow push a non-function on the stack? this should never happen
- return self::trigger( "internal error" );
- }
- }
- $index++;
- // ===============
- } elseif ( ', ' === $op and $expecting_op ) { // did we just finish a function argument?
- while ( ( $o2 = $stack->pop() ) != '(' ) {
- if ( is_null( $o2 ) ) {
- return self::trigger( "unexpected ', '" ); // oops, never had a (
- } else {
- $output[] = $o2; // pop the argument expression stuff and push onto the output
- }
- }
- // make sure there was a function
- if ( ! preg_match( "/^([A-Za-z]\w*)\($/", $stack->last( 2 ), $matches ) )
- return self::trigger( "unexpected ', '" );
- $stack->push( $stack->pop() + 1 ); // increment the argument count
- $stack->push( '(' ); // put the ( back on, we'll need to pop back to it again
- $index++;
- $expecting_op = false;
- // ===============
- } elseif ( '(' === $op and ! $expecting_op ) {
- $stack->push( '(' ); // that was easy
- $index++;
- // ===============
- } elseif ( $ex and ! $expecting_op ) { // do we now have a function/variable/number?
- $expecting_op = true;
- $val = $match[1];
- if ( preg_match( "/^([A-Za-z]\w*)\($/", $val, $matches ) ) { // may be func, or variable w/ implicit multiplication against parentheses...
- if ( in_array( $matches[1], self::$fb ) or array_key_exists( $matches[1], self::$f ) ) { // it's a func
- $stack->push( $val );
- $stack->push( 1 );
- $stack->push( '(' );
- $expecting_op = false;
- } else { // it's a var w/ implicit multiplication
- $val = $matches[1];
- $output[] = $val;
- }
- } else { // it's a plain old var or num
- $output[] = $val;
- }
- $index += strlen( $val );
- // ===============
- } elseif ( ')' === $op ) { // miscellaneous error checking
- return self::trigger( "unexpected ')'" );
- } elseif ( in_array( $op, $ops ) and ! $expecting_op ) {
- return self::trigger( "unexpected operator '$op'" );
- } else { // I don't even want to know what you did to get here
- return self::trigger( "an unexpected error occurred" );
- }
- if ( strlen( $expr ) == $index ) {
- if ( in_array( $op, $ops ) ) { // did we end with an operator? bad.
- return self::trigger( "operator '$op' lacks operand" );
- } else {
- break;
- }
- }
- while ( substr( $expr, $index, 1 ) == ' ' ) { // step the index past whitespace (pretty much turns whitespace
- $index++; // into implicit multiplication if no operator is there)
- }
- }
- while ( ! is_null( $op = $stack->pop() ) ) { // pop everything off the stack and push onto output
- if ( '(' === $op ) {
- return self::trigger( "expecting ')'" ); // if there are (s on the stack, ()s were unbalanced
- }
- $output[] = $op;
- }
- return $output;
- }
- /**
- * Evaluate postfix notation.
- *
- * @param mixed $tokens
- * @param array $vars
- *
- * @return mixed
- */
- private static function pfx( $tokens, $vars = array() ) {
- if ( false == $tokens ) {
- return false;
- }
- $stack = new WC_Eval_Math_Stack;
- foreach ( $tokens as $token ) { // nice and easy
- // if the token is a binary operator, pop two values off the stack, do the operation, and push the result back on
- if ( in_array( $token, array( '+', '-', '*', '/', '^' ) ) ) {
- if ( is_null( $op2 = $stack->pop() ) ) return self::trigger( "internal error" );
- if ( is_null( $op1 = $stack->pop() ) ) return self::trigger( "internal error" );
- switch ( $token ) {
- case '+':
- $stack->push( $op1 + $op2 );
- break;
- case '-':
- $stack->push( $op1 - $op2 );
- break;
- case '*':
- $stack->push( $op1 * $op2 );
- break;
- case '/':
- if ( 0 == $op2 ) {
- return self::trigger( 'division by zero' );
- }
- $stack->push( $op1 / $op2 );
- break;
- case '^':
- $stack->push( pow( $op1, $op2 ) );
- break;
- }
- // if the token is a unary operator, pop one value off the stack, do the operation, and push it back on
- } elseif ( '_' === $token ) {
- $stack->push( -1 * $stack->pop() );
- // if the token is a function, pop arguments off the stack, hand them to the function, and push the result back on
- } elseif ( ! preg_match( "/^([a-z]\w*)\($/", $token, $matches ) ) {
- if ( is_numeric( $token ) ) {
- $stack->push( $token );
- } elseif ( array_key_exists( $token, self::$v ) ) {
- $stack->push( self::$v[ $token ] );
- } elseif ( array_key_exists( $token, $vars ) ) {
- $stack->push( $vars[ $token ] );
- } else {
- return self::trigger( "undefined variable '$token'" );
- }
- }
- }
- // when we're out of tokens, the stack should have a single element, the final result
- if ( 1 != $stack->count ) {
- return self::trigger( "internal error" );
- }
- return $stack->pop();
- }
- /**
- * Trigger an error, but nicely, if need be.
- *
- * @param string $msg
- *
- * @return bool
- */
- private static function trigger( $msg ) {
- self::$last_error = $msg;
- if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
- echo "\nError found in:";
- self::debugPrintCallingFunction();
- trigger_error( $msg, E_USER_WARNING );
- }
- return false;
- }
- /**
- * Prints the file name, function name, and
- * line number which called your function
- * (not this function, then one that called
- * it to begin with)
- */
- private static function debugPrintCallingFunction() {
- $file = 'n/a';
- $func = 'n/a';
- $line = 'n/a';
- $debugTrace = debug_backtrace();
- if ( isset( $debugTrace[1] ) ) {
- $file = $debugTrace[1]['file'] ? $debugTrace[1]['file'] : 'n/a';
- $line = $debugTrace[1]['line'] ? $debugTrace[1]['line'] : 'n/a';
- }
- if ( isset( $debugTrace[2] ) ) $func = $debugTrace[2]['function'] ? $debugTrace[2]['function'] : 'n/a';
- echo "\n$file, $func, $line\n";
- }
- }