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===This action allows you to put calculations (with variables or not) and write out the result.===

==Basic usage==
By typing:
%%
1 day ={{calc 24*60*60}} seconds
%%
you will obtain:
1 day =86400 seconds

==With variables usage==
By typing:
%%
{{calc total=0}}
- red: {{calc q=2;total+=q;q}}
- blue: {{calc q=3;total+=q;q}}
- yellow: {{calc q=6;total+=q;q}}
- **total**: **{{calc total}}**
- **total+taxes**: **{{calc total+total*18.6/100.0}}**
%%
You will obtain:
- red: 2
- blue: 3
- yellow: 6
- **total**: **11**
- **total+taxes**: **13.046**
Because:
- Several expressions separated by a semicolon can appear in a **calc** action,
- only those that aren't assignations (not containing the equal sign) are displayed.

==Features==
- Secure
- The variables are keys in an associative array named calcvar (//i.e. calcvar['total']//)
- The function calls are forgotten.
- Powerful
- It makes your wiki page a spreadsheet.
- It allows displaying not hard-coded numerical values (such the number of seconds in a day), preventing errors...
- It allows modification of values in a page without recalculation by-hand of a global result (if you add an item //green: 12// in the list)


==Restrictions==
- Variables names are necessary alphabetics (see line 14).
- You can't (because of security) call functions (see line 28).
- A few operators are allowed (see line 16).

==Improvements==
- You can easily add an operator (currently -*/+) by adding a char in the regexp line 16.
- You could authorize the call of specific functions (such ln, exp,...) by matching them (a little bit more difficult)
- You could define options in order to set the precision of the result by example.

==Code==
Save this as actions/calc.php
%%(php;1)
<?php

/*
*Author:Jean-fran├žois Delesse (jfdelesse@free.fr)
*
*/
if (!function_exists('strtonum'))
{
$calcvar=array();
function strtonum($str)
{
static $calcvar;
$pattern = '/([^;])+/';
$varpat='([a-zA-Z]+\s*\(*)';
$varpattern="/$varpat/";
$otherpat='([0-9\.*\(\)\-+\/=]+)';
$allpattern="/$varpat|$otherpat/";
preg_match_all($pattern,$str,$blocks);
foreach ($blocks[0] as $k=>$block)
{
$affichage=true;
$blockstr="";
preg_match_all($allpattern,$block,$out,PREG_SET_ORDER);
foreach ($out as $k2=>$token)
{
if ($token[1]!="")
{
$token[1]=preg_replace('/\s*\(*/','',$token[1]);
$tokstr='$calcvar[\''.$token[1].'\']';
}
if ($token[2]!="")
{
$tokstr=$token[2];

if (!(strpos($tokstr,"=")===false))
{
$affichage=false;
}
}
$blockstr.=$tokstr;
}
if(!empty($blockstr))
{
$blockstr="$blockstr;";
$blockstr=eval("return ".$blockstr);
if ($affichage)
$outstr.=($outstr!=""?";":"").$blockstr ;
}
}
return $outstr;
}
}

if (is_array($vars))
{
print strtonum($vars['wikka_vars']);
}
?>
%%
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