From 1b71c53e1d16d88f566b781c1e93aef426a5e1ee Mon Sep 17 00:00:00 2001
From: fiedorow <fiedorow>
Date: Tue, 30 Mar 2004 17:11:56 +0000
Subject: [PATCH] Bug fix for incorrect handling of negatives in equations and
 inequalities

---
 filter/algebra/AlgParser.pm     | 2 +-
 filter/algebra/algebradebug.php | 2 ++
 filter/algebra/filter.php       | 2 ++
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/filter/algebra/AlgParser.pm b/filter/algebra/AlgParser.pm
index 4398293052..6ab1e7967a 100755
--- a/filter/algebra/AlgParser.pm
+++ b/filter/algebra/AlgParser.pm
@@ -42,7 +42,7 @@ $binoper1 = '[-+=><%!#]';
 $openparen = '[{(\\[]';
 $closeparen = '[})\\]]';
 $varname = '[A-Za-z](?:_[0-9]+)?';
-$specialvalue = '(?:e|pi|da|db|dc|de|df|dg|dh|di|dj|dk|dl|dm|dn|do|dp|dq|dr|ds|dt|du|dv|dw|dx|dy|dz|infty|alpha|bita|gamma|zita|thita|iota|kappa|lambda|mu|nu|xi|rho|sigma|tau|phi|chi|psi|omega|zepslon|zdelta|xeta|zupslon)';
+$specialvalue = '(?:e|pi|da|db|dc|de|df|dg|dh|di|dj|dk|dl|dm|dn|do|dp|dq|dr|ds|dt|du|dv|dw|dx|dy|dz|infty|alpha|bita|gamma|zita|thita|iota|kappa|lambda|mu|nu|xi|rho|sigma|tau|phi|chi|psi|omega|zepslon|zdelta|xeta|zupslon|zeroplace)';
 $numberplain = '(?:\d+(?:\.\d*)?|\.\d+)';
 $numberE = '(?:' . $numberplain . 'E[-+]?\d+)';
 $number = '(?:' . $numberE . '|' . $numberplain . ')';
diff --git a/filter/algebra/algebradebug.php b/filter/algebra/algebradebug.php
index caff0f6311..c5af44fe18 100644
--- a/filter/algebra/algebradebug.php
+++ b/filter/algebra/algebradebug.php
@@ -74,6 +74,7 @@ function algebra2tex($algebra) {
   $algebra = str_replace('<>','#',$algebra);
   $algebra = str_replace('<=','%',$algebra);
   $algebra = str_replace('>=','!',$algebra);
+  $algebra = preg_replace('/([=><%!#] *)-/',"\$1 zeroplace -",$algebra);
   $algebra = str_replace('delta','zdelta',$algebra);
   $algebra = str_replace('beta','bita',$algebra);
   $algebra = str_replace('theta','thita',$algebra);
@@ -95,6 +96,7 @@ function algebra2tex($algebra) {
 }
 
 function refineTeX($texexp) {
+  $texexp = str_replace('zeroplace','',$texexp);
   $texexp = str_replace('#','\not= ',$texexp);
   $texexp = str_replace('%','\leq ',$texexp);
   $texexp = str_replace('!','\geq ',$texexp);
diff --git a/filter/algebra/filter.php b/filter/algebra/filter.php
index c38cda28a0..81947657f2 100644
--- a/filter/algebra/filter.php
+++ b/filter/algebra/filter.php
@@ -150,6 +150,7 @@ function algebra_filter ($courseid, $text) {
            $algebra = str_replace('<>','#',$algebra);
            $algebra = str_replace('<=','%',$algebra);
            $algebra = str_replace('>=','!',$algebra);
+           $algebra = preg_replace('/([=><%!#] *)-/',"\$1 zeroplace -",$algebra);
            $algebra = str_replace('delta','zdelta',$algebra);
            $algebra = str_replace('beta','bita',$algebra);
            $algebra = str_replace('theta','thita',$algebra);
@@ -169,6 +170,7 @@ function algebra_filter ($courseid, $text) {
            if (preg_match('/parsehilight/',$texexp)) {
              $text = str_replace( $matches[0][$i],"<b>Syntax error:</b> " . $texexp,$text);
            } else if ($texexp) {
+              $texexp = str_replace('zeroplace','',$texexp);
               $texexp = str_replace('#','\not= ',$texexp);
               $texexp = str_replace('%','\leq ',$texexp);
               $texexp = str_replace('!','\geq ',$texexp);
-- 
2.39.5