Is it possible to write a regex which would take input like 'sqrt(2 * (2+2)) + sin(pi/6)'
and transform it into '\sqrt{2 \cdot (2+2)} + \sin(\pi/6)'
?
The problem is the 'sqrt' and parentheses in it. It is obvious I can't simply use something like this:
/sqrt\((.?)\)/ -> \\sqrt{$1}
because this code would create something like this '\sqrt{2 \cdot (2+2)) + \sin(\pi/6}'
.
My solution: it simply go throw the string converted to char array and tests if a current substring starts with $latex
, if it does second for-cycle go from this point in different direction and by parentheses decides where the function starts and ends. (startsWith function)
Code:
public static function formatFunction($function, $latex, $input) {
$input = preg_replace("/" . $function . "\(/", $latex . "{", $input);
$arr = str_split($input);
$inGap = false;
$gap = 0;
for ($i = count($arr) - 1; $i >= 0; $i--) {
if (startsWith(substr($input, $i), $latex)) {
for ($x = $i; $x < count($arr); $x++) {
if ($arr[$x] == "(" || $arr[$x] == "{") { $gap++; $inGap = true; }
else if ($arr[$x] == ")" || $arr[$x] == "}") { $gap--; }
if ($inGap && $gap == 0) {
$arr[$x] = "}";
$inGap = false;
break;
}
}
}
$gap = 0;
}
return implode($arr);
}
Use:
self::formatFunction("sqrt", "\\sqrt",
"sqrt(25 + sqrt(16 - sqrt(49)) + (7 + 1)) + sin(pi/2)");
Output:
\sqrt{25+\sqrt{16-\sqrt{49}}+(7+1)}+\sin (\pi/2)
Note: sin
and pi
aren't formated by this code, it's only str_replace
function...