Hey guys i need to do a program that simulates a coinflip and give out head or number.I did that
a = rand(1..2)
if a == 1 then
puts "HEAD!"
else
puts "NUMBER!"
end
enter = gets
if enter == "\n"
a = rand(1..2)
if a == 1 then
puts "HEAD!"
else
puts "NUMBER!"
end
end
but how can i include everytime you press enter it should continue and continue simulating coinflip like ... HEAD (enter) HEAD (enter) NUMBER (enter) and so on.
You need some kind of loop, not just an if. Here's a short way to do it:
loop do
puts ['HEAD', 'NUMBER'].sample
break if gets != "\n"
end
Or if you're ok with stopping by pressing CTRL-C:
loop do
puts ['HEAD', 'NUMBER'].sample
gets
end
Using a post-loop test (i.e., do the gets and possibly break after printing the flip result) is more appropriate here, as it avoids the code duplication. Also see this popular Ruby style guide:
https://github.com/bbatsov/ruby-style-guide#loop-with-break
https://github.com/bbatsov/ruby-style-guide#infinite-loop
Related
I'm doing a pwd generator in ruby and when I get to a certain point of the code I need to return back if the user says that he want to retry to generate the pwd.
print "do you want to retry to generate the password? [y/n]"
retrypwd = gets.chomp
if retrypwd == y
(code to jump to some lines ago)
elsif retrypwd == n
print "Ok, It'll be for the next time"
end
The trick is to use a loop and break it or repeat it according to your expectations:
def try_again?
loop do
print "Would you like to try again? Y/N"
again = gets.chomp.capitalize
case (again)
when 'N'
return false
when 'Y'
return true
else
puts "Huh? I don't know what that means."
end
end
end
Then you can incorporate this into your main program:
begin
try_password
end while try_again?
You will keep trying passwords until try_again? returns false, which happens if you type "N".
So I've been messing around with Ruby for the first time after finishing the codecademy course up to "Object Oriented Programming, Part I" and I decided to start making a calculator. For some reason though, I get this error:
calc.rb:13:in `addition': undefined local variable or method `user_input' for main:Object (NameError)
from calc.rb:21:in `<main>'
I'm confused why it doesn't see my "user_input" array. Is it out of the scope of the method? Did I initialize it wrong?
Here's the code so you can see for yourself, it's obviously nothing sophisticated and it's not finished. I'm just trying to test for addition right now.
#!/usr/bin/env ruby
user_input = Array.new
puts "Would you like to [a]dd, [s]ubtract, [m]ultiply, or [d]ivide? "
type_of_math = gets.chomp
def addition
operator = :+
puts "Please enter the numbers you want to add (enter \"=\" to stop adding numbers): "
until gets.chomp == "="
user_input << gets.chomp.to_i
end
sum = user_input.inject(operator)
return sum
end
case type_of_math
when "a"
addition
when "s"
puts "Test for subtraction"
when "m"
puts "Test for multiplication"
when "d"
puts "Test for division"
else
puts "Wrong"
end
Consider this untested variation on your code. It's more idiomatic:
def addition
user_input = []
puts 'Please enter the numbers you want to add (enter "=" to stop adding numbers): '
loop do
input = gets.chomp
break if input == '='
user_input << input
end
user_input.map(&:to_i).inject(:+)
end
Notice that it puts user_input into the method. It also uses the normal [] direct assignment of an empty array to initialize it. Rather than chomp.to_i each value as it's entered it waits to do that until after the loop exits.
Instead of while loops, consider using loop do. They tend to be more easily seen when scanning code.
Also notice there's no return at the end of the method. Ruby automatically returns the last value seen.
Basically in my search for code which will loop, and terminate upon user input, i managed to find code here, and after some alteration, produced this:
#desired destination method, however loop persists!!
def desired_method
print "method entered"
end
Thread.new do
while line = STDIN.gets
break if line.chomp == "" # code detects user input
end
desired_method
end
# program will loop here until user presses enter
loop do
puts "foo"
sleep 1
end
This code is brilliant, and will enter the method 'desired_method' when i hit enter, however the loop persists!! printing 'foo' perpetually after "method entered"!!. I have done some research prior to posting this question on how to kill threads, which i believe may hold the answer. My attempts included naming the thread and using the 'thread.exit' function to kill it, however these techniques have remained unsuccessful.
Can anyone illustrate how i might enter the 'desired_method' method without the persisting "foo" print?
Thanks in advance, and greatly appreciated.
An easy solution here is to use semaphore, signalling between threads with a variable access to both places:
# This will be out stop flag, for signalling between threads.
#time_to_stop = false
def desired_method
print "method entered"
# Here we want the loop in the other thread to stop.
#time_to_stop = true
end
Thread.new do
while line = STDIN.gets
break if line.chomp == "" # code detects user input
end
desired_method
end
# program will loop here until user presses enter
loop do
puts "foo"
sleep 1
# only continue if the stop flag is not set.
break if #time_to_stop
end
Hope this helps.
I'm curious if there's a way to have the program go back up the if statement stack?
Ideally, the program would return to line 2 and prompt the user for the input variable, then continue to evaluate like it did the first time. Think of it like a cursor in a text editor, I just want to move it from either of those two comments back up to line 2. The two places of interest are commented out below:
while true
input = gets.chomp
if input != input.upcase
puts "HUH?! SPEAK UP, SONNY!"
elsif input == 'BYE'
puts "HUH?! SPEAK UP, SONNY!"
input = gets.chomp
if input == 'BYE'
puts "HUH?! SPEAK UP, SONNY!"
input = gets.chomp
if input == 'BYE'
puts "GOOD BYE!";
break
else
# return to top-level if statement
end
else
# return to top-level if statement
end
else
random_year = rand(1930..1950)
puts "NO, NOT SINCE #{random_year}!"
end
end
In the code you show, you don't need to do anything to make the flow of execution go back to line 2. Just omit the else clauses in the two places you marked. The flow of execution will drop down to the bottom of the while loop, then loop back to the top, then go back to line 2.
You need to use a while statement to set a condition flag and check it, which will loop back to the while statement if you don't change the flag:
flag = 0
while flag1 == 0
if var = "string"
then ...statements...
flag1 = 1 ; this allows us to break out of this while loop
else ...statements...
end
end
If flag1 is not 0 at the end of the while statement, the while statement will loop back. For two such conditions, you need to nest the while loops. You might have to re-order your statements to make multiple while loops work this way.
You can avoid this level of neasted ifs with:
byecount = 0
while byecount < 3
input = gets.chomp
if input == "BYE"
byecount += 1
next
else
byecount = 0
end
if input != input.upcase
puts "HUH?! SPEAK UP, SONNY!"
else
puts "NO, NOT SINCE #{rand(1930..1950)}!"
end
end
puts "GOOD BYE!"
Or you can write a catch..throw flow structure. (Really.. if you need to use it, something is wrong with your design)
catch :exitloop do
while ...
if ...
if ...
if ...
throw :exitloop
end
end
end
end
end
Here's how I'd write a similar exercise:
BYE = 'BYE'
HUH = "HUH?! SPEAK UP, SONNY!"
loop do
input = gets.chomp
if input != input.upcase
puts HUH
next
end
if input != BYE
random_year = rand(1930..1950)
puts "NO, NOT SINCE #{random_year}!"
next
end
puts HUH
input = gets.chomp
if input == BYE
puts HUH
input = gets.chomp
if input == BYE
puts "GOOD BYE!";
break
end
end
end
I used loop instead of while. Matz, the main man for Ruby, recommends loop. See "Is there a “do … while” loop in Ruby?" for further discussion about it.
I need a way to pause the program's flow because there are a lot of print statements that I want to check first. is there a way to do this with ruby, stop the program's flow and continue only if the user has entered yes or stop if it has entered no ? thanks
Yes. In your code, put gets. Then the code will pause at that point until the user inputs Enter. You don't need to do anything special to terminate because, if you want to, you can just do Ctrl+C.
Don't forget to chomp off the newline from the return value of gets.
n, m = 0, 1
repeat = 10
loop do
repeat.times do
print "#{m}, "
n, m = m, n + m
end
puts "\nContinue (yes/no)?"
answer = gets.chomp
exit if answer == "no"
end
Also check out Pry.
# test.rb
require 'pry'
class A
def hello() puts "hello world!" end
end
a = A.new
# start a REPL session
binding.pry
# program resumes here (after pry session)
puts "program resumes here."