PL/SQL :: Using Recursive Subquery Factoring In A Function?

I need to use Recursive Subquery Factoring for a project of mine, specifically I need to use some code I have found in a function.

[URL]

The code I have so far is this:

create or replace
function recursive
(
pattern in raw
, solution in raw
) return number as

[code]....

But when trying to compile it in Oracle SQL Developer, I get the following two errors:

Error(9,1): PL/SQL: SQL Statement ignored
Error(10,30): PL/SQL: ORA-00907: missing right parenthesis

The errors refer to these two lines:

with x( s, ind ) as
( select sud, instr( sud, '' '' )

I have looked over and over the code again, and I do not see any missing parenthesis. Furthermore I tried using with in a smaller test function:

create or replace function test
(
p in number
)
return number as
v number;
begin
with t(a) as

[code]....

Which compiles just fine, so I'm not sure why that line is being ignored in this function. The whole idea here is to replace the sudoku string in the function with a variable that I built from the two parameters.