# [✓] Concatenate elements in a list?

GROUPS:
 I'm very new to Mathematica, so here comes a newbie question.I have a list of numbers, such as {12,35}, and want to concatenate them to produce a single-element list: {1235} in this example. I then want to extract that element as an integer, 1235. Can someone please give me a clue.Geoffrey Marnell
 Patrick Scheibe 2 Votes You can turn a number into a list of its digits using IntegerDigits. If you do that on all your numbers, you have a list where each element is a list of digits. Then you can Flatten this list to get one long list of digits. After that, you rebuild a new Integer. FromDigits[Flatten[IntegerDigits[{12, 35}]]] (* 1235 *) 
 Christopher French 2 Votes Beat me to it!IntegerDigits will break up the numbers, into sub-lists IntegerDigits@{12, 35} {{1, 2}, {3, 5}}Flatten will break up the sub-lists Flatten@IntegerDigits@{12, 35} {1, 2, 3, 5}FromDigits will make a new integer from the flattened list FromDigits@Flatten@IntegerDigits@{12, 35} 1235RightComposition allows the operations to be read from left to right {12, 35} // RightComposition[IntegerDigits, Flatten, FromDigits] 1235Another way of saying RightComposition is /* RightComposition[ IntegerDigits, Flatten, FromDigits] IntegerDigits /* Flatten /* FromDigitsMake a compound operation called joinDigits, or as you like joinDigits = IntegerDigits /* Flatten /* FromDigits; Call the new operation on your list joinDigits[{12, 35}] 1235 joinDigits[{12, 35, 69}] 123569