Function to convert string to number

Question

Hi there,
I wrote a function which converted a hor minute component of a date to a number. Now I need to do the same with a string (because the hours could be more then 23:95). Anyway here is my function. How can I rewrite it so it will accept a string as in parameter. Somwhow I can not work it out. Thanks a lot.
Chris
function calculate_hours_project(in_hours in DATE)
RETURN number
AS
hrs CHAR(2);
mins CHAR(2);
     BEGIN
          hrs := to_char(in_day, 'HH24');
          mins := to_char(in_day, 'MI');
          if hrs is not null and mins is not null then
          RETURN to_number(hrs + (mins/60));
          else
          RETURN 0;
          end if;
END calculate_hours_project;

Answer 1

Wouldn't it just be something like this?
sql>create or replace function calculate_hours_project(in_hours in varchar2)
  2  return number
  3  is
  4  begin
  5    return to_number(substr(in_hours, 1, instr(in_hours, ':') - 1)) +
  6           to_number(substr(in_hours, instr(in_hours, ':') + 1) / 60);
  7  end calculate_hours_project;
  8  /
Function created.
sql>select calculate_hours_project('08:05') from dual;
CALCULATE_HOURS_PROJECT('08:05')
                       8.0833333
1 row selected.
sql>select calculate_hours_project('35:34') from dual;
CALCULATE_HOURS_PROJECT('35:34')
                       35.566667
1 row selected.