Initial implementation of the time module

[gptsarthak]

For timing the benchmarks, we currently use the bash time command. But that only provides the time in millisecond. Python's time.time() method outputs time in a much higher precision.

I have implemented the time.time() method here using Unix Time after understanding timemodule.c

Here is an example:

import time

def fibonacci(n : i32) -> i32:
    if n <= 1:
        return n
    return fibonacci(n-1) + fibonacci(n-2)

def main():
    print("Current time : ", time.time())
    start_time : f64 = time.time()
    a : i32 = fibonacci(35)
    print("Answer: ", a)
    print("Time taken : ", time.time()-start_time)

main()

(base) sarthak@pop-os:~/lpython$ python examples/timetest.py
Current time :  1680876878.893159
Answer:  9227465
Time taken :  2.6417429447174072
(base) sarthak@pop-os:~/lpython$ lpython examples/timetest.py
Current time :  1.68087688629948306e+09          // Decimal : 1680876886.29948306
Answer:  9227465
Time taken :  7.29780197143554688e-02            // Decimal : 0.0729780197143554688

I will add tests after a review.

[certik]

@gptsarthak perfect, thanks for this! I left some comments.

[gptsarthak]

I have removed the use of <sys/time> and added the implementation of time for Windows. However, this needed us to include a new header <winsock2.h> (a part of <windows.h>).

CPython Reference used for implementation : pytime.c#L871

Why not using the _lfortran_cpu_time function that is already implemented? It should work and at least it compiles on Windows, even if not implemented yet.

I could not use that function becuase it uses clock() from time.h which does not give the same output as CPython.
Same example ran in Windows:

(lp) C:\Users\gptsa\lpython>python examples\timetest.py
Current time :  1680962365.4241385
Answer:  9227465
Time taken :  6.094292402267456

(lp) C:\Users\gptsa\lpython>src\bin\lpython examples\timetest.py
Current time :  1.68096238567989349e+09
Answer:  9227465
Time taken :  1.15024566650390625e-01

[certik]

I think this looks good, thanks!

[certik]

@gptsarthak do you want to add some tests in a subsequent PR?