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Problem background -- I want to get the nth root of the number where user can enter expression like "the nth root of x'.I have written a function nthroot(x,n) which return proper expected output.My problem is to extract the value of x and n from expression.

I want to extract some matched pattern and store it to a an array for further processing so that in next step i will pop two elements from array and replace the result in repression.But I am unable to get all the values into an array without using loop.

A perl equivalent of my code will be like below.

$str = "the 2th root of 4+678+the 4th root of -10000x90";
@arr = $str =~ /the ([-+]?\d+)th\s?root\s?of\s?([-+]?\d+)/g;
print "@arr";

I want the javascript equivalent of the above code.

or

any one line expression like below.

expr = expr.replace(/the\s?([+-]\d+)th\s?root\s?of([+-]\d+)/g,nthroot(\\$2,\\$1));

Please help me for the same.

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can numbers be in hexadecimal form -10000x90?? – Anirudh 32 mins ago
and what is 4+678 in your input – Anirudh 31 mins ago
no 'x' can be used instead of '*'. x is for multiplication operation. – virus 30 mins ago
$str = "the 2th root of 4+678+the 4th root of -10000x90"; basically it is a mathematical expression.User is allowed to enter in above form.So I need to convert it to its mathematical equivalent "2+678+(7.07106781+7.07106781i)*90" where i is root of -1(Complex number). – virus 26 mins ago

2 Answers

up vote 1 down vote

The .replace() method that you are currently using is, as its name implies, used to do a string replacement, not to return the individual matches. It would make more sense to use the .match() method instead, but you can (mis)use .replace() if you use a callback function:

var result = expr.replace(/the\s?([+-]\d+)th\s?root\s?of([+-]\d+)/,function(m,m1,m2){
  return nthroot(+m2, +m1);
});

Note that the arguments in the callback will be strings, so I'm converting them to numbers with the unary plus operator when passing them to your nthroot() function.

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up vote 0 down vote 
var regex=/the ([-+]?\d+)th\s?root\s?of\s?([-+]?\d+)/g;
expr=expr.replace(regex, replaceCallback); 

var replaceCallback = function(match,p1,p2,offset, s) { 
 return nthroot(p2,p1);
 //p1 and p2 are similar to $1 $2
}
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