Remove Duplicates From One List

Question

Task:

Remove all duplicates from one list of integers. A list is simply a sequence of connected values that allows the same values to be stored at different positions in this sequence.

If an item was found to be the same value as another item in this list, keep the first occurence of the item and remove the second (third and so on...) occurence of the item.

Input/Output

You may write a function or full program that takes a list of integers as an input and returns a list without duplicates as an output.

Rules:

• This is a code-golf challenge, so shortest answer wins!

Answer 1

APL (1)

∪

∪ takes a list and returns the unique elements in a list, i.e.:

    ∪ 1 2 3 2 3 4 5
1 2 3 4 5

if you need I/O it's 2:

∪⎕

Answer 2

GolfScript (2 bytes)

.&

Takes input on stack, leaves output on stack.

Answer 3

Red, 8 bytes

unique s

assuming list is in word 's

Answer 4

Python 2: 12 bytes

print set(l)

No input spec, so I'm assuming the list is held in a variable called l.

Answer 5

Python - 12 bytes

list(set(l))

Assuming the list is given in the variable l.

Answer 6

Mathematica, 7 bytes or 3 characters

Assumes input in variable x

Union@x

If we're counting in Mathematica characters, I can do 3 (the second input line):

Answer 7

Ruby, 3 characters

a|a

Assumes the list is stored in variable a. Also works with & instead of |.

If the original list has to be altered (instead of keeping the original the same and creating a new list with duplicates removed), then 4 characters:

a|=a