wikimedia/mediawiki-extensions-ParserFunctions
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Adds explicit round-off checking to operations that are sensitive to floating point vs. integer round-off errors.

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Where applied, it assumes that any floating point number that is an integer to within one part in 10^10 should be replaced with that integer.
This commit is contained in:
Robert Rohde 2009-02-01 03:56:24 +00:00
parent de9b42156f
commit 8f6382337c
1 changed files with 35 additions and 12 deletions
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47
Expr.php
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@ -152,6 +152,29 @@ class ExprParser {
'pi' => EXPR_PI,
);
/**
* Checks if $expr is an integer within one part in 10^10.
* If so, recast as integer and return, else return $expr unchanged.
*
* Explicit checking for round-off errors should eliminate
* many bugs associated with floating point conversion to integers.
*/
function checkInteger( $expr ) {
$intval = (int)$expr;
if( $expr >= 0 ) {
if( $expr - $intval > 0.9999999999 ) { $intval += 1; }
} else {
if( $expr - $intval < -0.9999999999 ) { $intval -= 1; }
}
if( abs( $intval - $expr ) < 0.0000000001 ) {
return $intval;
} else {
return $expr;
}
}
/**
* Evaluate a mathematical expression
*
@ -400,7 +423,7 @@ class ExprParser {
$right = array_pop( $stack );
$left = array_pop( $stack );
if ( $right == 0 ) throw new ExprError('division_by_zero', $this->names[$op]);
$stack[] = $left % $right;
$stack[] = $this->checkInteger( $left ) % $this->checkInteger( $right );
break;
case EXPR_PLUS:
if ( count( $stack ) < 2 ) throw new ExprError('missing_operand', $this->names[$op]);
@ -430,7 +453,7 @@ class ExprParser {
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;
$stack[] = ( $this->checkInteger( $left ) == $this->checkInteger( $right ) ) ? 1 : 0;
break;
case EXPR_NOT:
if ( count( $stack ) < 1 ) throw new ExprError('missing_operand', $this->names[$op]);
@ -441,43 +464,43 @@ class ExprParser {
if ( count( $stack ) < 2 ) throw new ExprError('missing_operand', $this->names[$op]);
$digits = intval( array_pop( $stack ) );
$value = array_pop( $stack );
$stack[] = round( $value, $digits );
$stack[] = round( $this->checkInteger( $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;
$stack[] = ( $this->checkInteger( $left ) < $this->checkInteger( $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;
$stack[] = ( $this->checkInteger( $left ) > $this->checkInteger( $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;
$stack[] = ( $this->checkInteger( $left ) <= $this->checkInteger( $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;
$stack[] = ( $this->checkInteger( $left ) >= $this->checkInteger( $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;
$stack[] = ( $this->checkInteger( $left ) != $this->checkInteger( $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);
$stack[] = $left * pow(10, $this->checkInteger( $right ) );
break;
case EXPR_SINE:
if ( count( $stack ) < 1 ) throw new ExprError('missing_operand', $this->names[$op]);
@ -530,17 +553,17 @@ class ExprParser {
case EXPR_FLOOR:
if ( count( $stack ) < 1 ) throw new ExprError('missing_operand', $this->names[$op]);
$arg = array_pop( $stack );
$stack[] = floor($arg);
$stack[] = floor( $this->checkInteger( $arg ) );
break;
case EXPR_TRUNC:
if ( count( $stack ) < 1 ) throw new ExprError('missing_operand', $this->names[$op]);
$arg = array_pop( $stack );
$stack[] = (int)$arg;
$stack[] = (int)( $this->checkInteger( $arg ) );
break;
case EXPR_CEIL:
if ( count( $stack ) < 1 ) throw new ExprError('missing_operand', $this->names[$op]);
$arg = array_pop( $stack );
$stack[] = ceil($arg);
$stack[] = ceil( $this->checkInteger( $arg ) );
break;
case EXPR_POW:
if ( count( $stack ) < 2 ) throw new ExprError('missing_operand', $this->names[$op]);