DEC to HEX puzzler (see gist's revision for problem and diff to this solution)

decimal_to_hex_puzzler.groovy

/* THIS PUZZLER IS SOVLED, SEE REVISION OF THIS GIST TO SEE ORIGINAL PROBLEM */

decimalValue = 9989
hexValue = toHex(code)
assert hexValue == '2705'

// safe net
expectedValue = Integer.toHexString(decimalValue)
assert hexValue == expectedValue : "Your impl should work as expected. Result should be: ${expectedValue}"

println "DECIMAL VALUE: ${decimalValue} CONVERTED TO HEX VALUE: ${hexValue}"

/* ------------------------ METHODS -------------------------- */

/* 
   note you can use Java's Integer#toHexString()
   this is just for practicing purposes
*/
def toHex(number) {
    next = Double.valueOf(Math.floor(number / 16)).toLong()
    def remainder = number % 16    
    
    // debug print to see what happens inside of this method
    // println next + ", " + remainder
    
    // translate 10 -> A, 11->B .... 15->F
    if (remainder > 9) {
        remainder = (((int)'A') + (remainder - 10)) as char
    }
    
    // end recursion
    if (next == 0) {
        return remainder 
    }      
    
    return toHex(next) + remainder.toString()
}