Function array_to_string(text[], text) does not exist ???

Hi,

I'm trying to call the array_to_string function like this :
SELECT array_to_string(array[1, 2, 3], '~^~') --> it comes
directly from the doc.
I get this error msg :
ERROR: parser: parse error at or near "[" at character 24

So I tried this way
SELECT array_to_string('{1, 2, 3}', '~^~')
I get this error msg :
ERROR: Function array_to_string("unknown", "unknown") does
not exist
Unable to identify a function that satisfies the given argument
types
You may need to add explicit typecasts

So I tried to cast it
SELECT array_to_string(CAST('{1, 2, 3}' AS _int8),
CAST('~^~' AS text))
I get this error msg :
ERROR: Function array_to_string(bigint[], text) does not
exist
Unable to identify a function that satisfies the given argument
types
You may need to add explicit typecasts

Any help would be greatly appreciated.

Thanks