How to Convert Time as "HH:MM:SS" to a Numeric Value

• Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, and 2.5a
• Microsoft FoxPro for Windows, versions 2.5 and 2.5a

To convert a time string of the form "HH:MM:SS" to a numeric value, you must create a user-defined function (UDF). The following code is provided as an example.

   * TTON(<expC>)
   * Convert <expC> to a number of hours
   * Return value - Numeric
   * <expC> is a string of the form "HH:MM:SS". If <expC> doesn't
   * contain two colons (::), or time values are not in the range,
   * TTON returns -1.

   FUNCTION TTON
   PARAMETERS timestr
   PRIVATE pos1,pos2,hours,minutes,seconds

   * Get position of first and second occurrences of ':'
   pos1=at(':',timestr,1)
   pos2=at(':',timestr,2)

   * Error checking
   IF pos1==0 OR pos2==0
      RETURN -1
   ENDIF

   * Convert hh, mm and ss to numeric values and check for valid range
   hours = VAL(timestr)
   IF hours < 0 or hours > 24
      RETURN -1
   ENDIF
   minutes = VAL(SUBSTR(timestr,pos1+1))   && from 1st ':' to 2nd ':'
   IF minutes < 0 or minutes > 59
      RETURN -1
   ENDIF
   seconds=VAL(SUBSTR(timestr,IIF(LEN(timestr)>=pos2+1,pos2+1,0)))
   IF seconds < 0 or seconds > 59
      RETURN -1
   ENDIF

   * Convert minutes and seconds to decimal values
   minutes=minutes/60
   seconds=(seconds/60)/60

   * Return total value of hours, minutes and seconds
   RETURN ( hours+minutes+seconds )