A question/curiosity: When using the time function, why must the argument be 0, as "time(0)"? I tried other numbers and it gave error.
sgw 0 Junior Poster in Training
Danny_501 2 Junior Poster
nucleon 114 Posting Pro in Training
time's parameter is an alternate return path. If you pass in NULL (or 0) it is ignored. Otherwise, you must pass the address of a time_t object which will be filled with the time.
vmanes commented: Good clear answer! +8
tux4life 2,072 Postaholic
time(0); or time(NULL); returns the system time in seconds ...
The C++ Declaration of the 'time()'-function looks as follows: time_t time ( time_t * timer ); So if you pass a NULL-pointer as argument, it will just return the time ...
But between the brackets you can also type the name of a 'time_t' object and call the function with a 'time_t'-object as parameter ...
When doing this the function saves the system time (in seconds) to the 'time_t'-object ...
Hope this helps !
Source: http://www.cplusplus.com/reference/clibrary/ctime/time.html
tux4life 2,072 Postaholic
Wow, Sorry, I didn't read the thread carefully ...
I just see that nucleon did already explain why ...
nucleon 114 Posting Pro in Training
The more the merrier!
I wonder why it has that parameter, though.
Seems kind of pointless.
sgw 0 Junior Poster in Training
Thanks for the explanations, everyone!
ArkM 1,090 Postaholic
time(0);ortime(NULL);returns the system time in seconds ...The C++ Declaration of the 'time()'-function looks as follows:
time_t time ( time_t * timer );So if you pass a NULL-pointer as argument, it will just return the time ...
But between the brackets you can also type the name of a 'time_t' object and call the function with a 'time_t'-object as parameter ...
When doing this the function saves the system time (in seconds) to the 'time_t'-object ...
Source: http://www.cplusplus.com/reference/clibrary/ctime/time.html
Alas, the time() function does NOT return the system time in seconds. Regrettably, so an authoritative source as cplusplus.com presents an incorrect example of the time function usage.
The C language (7.23.1):
The range and precision of times representable in clock_t and time_t are implementation-defined.
So the size_t is an arithmetic type capable of representing times - that's all.
However the double difftime(time_t t1, time_t t0) function returns the difference t1-t0 expressed in seconds as a double.
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