Given a string, compute recursively a new string where all 'x' chars have been removed.

Sure, here is a recursive function that removes all 'x' characters from a given string:

def remove_x(string):
    # Base case: If the string is empty, return an empty string
    if not string:
        return ""

    # Recursive case: If the first character is 'x', skip it and recurse on the rest of the string
    if string[0] == 'x':
        return remove_x(string[1:])

    # Recursive case: If the first character is not 'x', keep it and recurse on the rest of the string
    return string[0] + remove_x(string[1:])

This function works by checking the first character of the string. If it's 'x', it skips that character and calls itself on the rest of the string. If it's not 'x', it keeps that character and calls itself on the rest of the string. The base case is when the string is empty, in which case it returns an empty string.