48 lines
2.1 KiB
Erlang
48 lines
2.1 KiB
Erlang
-module(chapter4).
|
|
-export([t2l/1, timeit/1]).
|
|
% 2. The BIF tuple_to_list(T) converts the elements of the tuple T to
|
|
% a list. Write a function called my_tuple_to_list(T) that does the
|
|
% same thing only not using the BIF that does this.
|
|
t2l(T) ->
|
|
[ element(I, T) || I <- lists:seq(1, tuple_size(T)) ].
|
|
|
|
% 3. Look up the definitions of erlang:now/0, erlang:date/0, and
|
|
% erlang:time/0. Write a function called my_time_func(F), which
|
|
% evaluates the fun F and times how long it takes. Write a function
|
|
% called my_date_string() that neatly formats the current date and
|
|
% time of day.
|
|
|
|
% erlang:time -> Returns the current time as {Hour, Minute, Second}.
|
|
% erlang:date -> Returns the current date as {Year, Month, Day}.
|
|
% erlang:now -> deprecated, should use erlang:timestamp
|
|
% erlang:timestamp -> Returns current Erlang system time on the format
|
|
% {MegaSecs, Secs, MicroSecs}.
|
|
% erlang:system_time(Unit) -> Returns current Erlang system time
|
|
% converted into the Unit passed as argument.
|
|
|
|
timeit(F) ->
|
|
Started = erlang:system_time(microsecond),
|
|
F(),
|
|
{erlang:system_time(microsecond) - Started, microsecond}.
|
|
|
|
% 4. Advanced: Look up the manual pages for the Python datetime
|
|
% module. Find out how many of methods in the Python datetime class
|
|
% can be implemented using the time-related BIFs in the erlang
|
|
% module. Search the erlang manual pages for equivalent
|
|
% routines. Implement any glaring omissions.
|
|
|
|
% 5. Write a module called math_functions.erl, exporting the functions
|
|
% even/1 and odd/1. The function even(X) should return true if X is an
|
|
% even integer and otherwise false. odd(X) should return true if X is
|
|
% an odd integer.
|
|
|
|
% 6. Add a higher-order function to math_functions.erl called
|
|
% filter(F, L), which returns all the elements X in L for which F(X)
|
|
% is true.
|
|
|
|
% 7. Add a function split(L) to math_functions.erl, which returns
|
|
% {Even, Odd} where Even is a list of all the even numbers in L and
|
|
% Odd is a list of all the odd numbers in L. Write this function in
|
|
% two different ways using accumulators and using the function filter
|
|
% you wrote in the previous exercise.
|