I am attempting to pass an array into a case statement so I can read the array elements as commands. Unfortunately, it seems that it is not working and the program jumps to the else statement.
def input_console()
quit = 0
puts "Tell me what you want to do:"
loop do
print "\n >>> "
input = gets.chomp
sentence = input.split
case sentence
when sentence[0] == "go" && sentence[1] == "to"
puts sentence[2]
when sentence[0] == "quit"
quit = 1
else
puts "No le entiendo Senor..."
end
break if quit == 1
end
end
This piece of code returns "No le entiendo Senor..." whatever you introduce. I expected to get the place I want to go after stating "go to Wherever".
Please, ¿may you help me?
You can do this by making your case statement independent of a specific variable.
change
case sentence
to
case
Here is an example of how you would use case-when while checking for values in the array.
numbers = [1,2,3]
case
when a[1] == 2
p "two"
else
p "nothing"
end
So in your case you can just say
case
when sentence[0] == "go" && sentence[1] == "to"
puts sentence[2]
when sentence[0] == "quit"
quit = 1
else
puts "No le entiendo Senor..."
end
Why are you making this a case statement? (And why is quit a Fixnum rather than a boolean? Actually, why have it at all?)
while true
# ... prompt and get input ...
if sentence[0] == "go" && sentence[1] == "to"
puts sentence[2]
elsif sentence[0] == "quit"
break
else
puts "No le entiendo Senor..."
end
end
You could use regular expressions. Something like this:
case gets
when /\Ago to (.*)\Z/
puts $1
when /\Aquit\Z/
# handle quit
else
puts "No le entiendo Senor..."
end
\A matches the beginning of string and \Z matches just before the trailing newline, so you don't need chomp.
Related
I am new to Ruby. I have written the code below, its working about 90% except the else statement. The else statement triggers endless loop. I just want it to ask user to try again. Here is my code
puts "Do you want to print something? (Y / N)"
user = gets.chomp.downcase
answer = true
while answer
if user == "y"
puts "Something"
answer = false
elsif user == "n"
puts " "
answer = false
else
puts "Invalid input! Please enter Y or N"
end
end
Somewhat shorter (note user has gone, the answer is now referred to as answer).
answer = ""
until (answer == "y") or (answer == "n")
puts 'Do you want to print something? (Y/N)'
answer = gets.chomp.downcase
end
Once you exit the else, answer is still true. If you want to re-prompt, you can move your puts and user statement into the loop.
Something like this should work.
while true # (alternately) loop do
puts 'Do you want to print something? (Y/N)'
case gets.chomp.downcase
when 'y'
puts 'foo'
break
when 'n'
puts 'bar'
break
else
puts 'Invalid input! Please enter Y or N'
end
end
You can use break to exit out of your loop instead of setting up another variable. Also, this looks like a good use-case for a case statement to have some explicit cases listed.
EDIT: Someone pointed out that I needed to break correctly so I am editing the question
Scenario:
Please see following code:
print "UserID: "
uid = $stdin.gets.chomp
print "Password: "
pwd = $stdin.gets.chomp
usr_inp = "#{uid};#{pwd}"
login_status = -1
# login_info.txt - "#{userid};#{password}" - format
File.open(File.join(File.dirname(__FILE__), 'login_info.txt'), "r") do |f|
f.each_line do |line|
puts line
if (line.chomp == usr_inp)
login_status = 1
elsif (line.chomp != usr_inp && line.include?(uid)) #case a person inputs invalid password
login_status = 0
elsif (line.chomp != usr_inp && !(line.include?(uid))) #case a person inputs an invalid id
login_status = 2
end
end
end
if (login_status == 1)
puts "\nLogged in successfully: #{uid}"
elsif (login_status == 2)
puts "\nSorry, that Employee does not exist."
elsif (login_status == 0)
puts "\nLogin failed.\nPlease check credentials."
end
Problem:
break if (condition) exists in Ruby. But I don't waht that.
I want to do something like:
if (condition x)
(do something)
break
elsif (condition y)
(do something else)
break
else
(whatever)
end
Maybe I am not understanding how ruby code works. Whenever I try to put the break as I want to use it, it associates with the next elsif.
Please help.
It depends on what you need and where you need it.
A script like this:
condition = 1
case condition
when 1
puts 'one'
break
when 2
puts 'two'
else
puts 'Other %s' % condition
end
puts 'end'
has a syntax error. break leaves a loop and there is no loop.
But with a loop, this works:
[1,2,3].each{|condition|
case condition
when 1
puts 'one'
break
when 2
puts 'two'
else
puts 'Other %s' % condition
end
puts 'end'
}
puts 'very end'
The output is:
one
very end
You see, the loop is stopped.
If you want to continue the loop with the next element, you need next (sorry, I'm just not aware what break is doing really in Java - it's been a long time since my last Java program):
[1,2,3].each{|condition|
case condition
when 1
puts 'one'
next
when 2
puts 'two'
else
puts 'Other %s' % condition
end
puts 'end %s' % condition
}
puts 'very end'
The result:
one
two
end 2
Other 3
end 3
very end
When you are not inside a loop (like in your code snippet), you may use exit (leave the program) or return (leave a method).
I don't really know how to word this short enough for me to google it.
But is it possible to execute a certain condition in a multiple condition while loop differently, without creating a whole entire while loop.
For example, Is it possible to do something like this
while num == "" || num == "0"
#ENTER CODE
Instead of doing this
while num == ""
print "YOU MUST ENTER A NUMBER!"
num = gets.chomp
end
while num == "0"
print "ZERO IS NOT A VALID NUMBER!"
num = gets.chomp
end
I want to know is it possible to do this, but make it look more visually appealing and concise.
This should do the trick, one loop and use conditionals for which error message to print.
while num == "" || num == "0"
print "YOU MUST ENTER A NUMBER!" if num == ""
print "ZERO IS NOT A VALID NUMBER!" if num == "0"
num = gets.chomp
end
You could write something like this:
while num.to_i.zero?
case number
when ''
print 'YOU MUST ENTER A NUMBER!'
when '0'
print 'ZERO IS NOT A VALID NUMBER!'
end
num = gets.chomp
end
This works, because to_i returns 0 for both the string "0" and nil.
Furthermore I would suggest to change the error message to simplify the code even more:
while num.to_i.zero?
print 'Please enter a number greater then zero'
num = gets.chomp
end
Is there a way to make this code shorter and simpler?
loop do
if possibleSet.split(" ").map(&:to_i).any? {|e| (e<0 || e>12)}
print "Please enter valid numbers (between 1 and 12): "
possibleSet = gets
errorinput = false
else
errorinput = true
end
break if errorinput
end
Refactored a bit :)
loop do
print "Please enter valid numbers (between 1 and 12): "
possibleSet = gets.chomp
break unless possibleSet.split(" ").map(&:to_i).any? {|e| (e<0 || e>12)}
end
The code below will check input for correctness:
input = loop do
print "Please enter valid numbers (between 1 and 12): "
# ⇓⇓⇓ as many spaces as user wants
input = gets.chomp.split(/\s+/).map(&:to_i) rescue []
break input unless input.empty? || input.any? { |i| !(0..12).include? i }
end
This parses the user input in an array (not exactly the same behavior, but I hope it is cleaner and you can work from there)
set = []
until set.all? {|i| (1..11).include?(i) } && !set.empty? do
set = gets.split(' ').map(&:to_i)
end
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.