I would like to make a program that checks to see if the number you enter is an even number. Sort of like making a leap year program but for any number divisible by 2.
Something along the lines of:
num = gets.chomp
while num != 0
if (num%2) == 0
puts 'yess'
else
puts 'nooo'
end
end
I knows there's something easy that I need to change for it to run.
(btw I just started learning Ruby yesterday!)
There are two problems here.
First being something that others have put, you need to make sure you turn the input into an integer using ".to_i" on your num variable.
Secondly, this code puts you into an infinite loop since you are using a "while" loop.
Since the number is only input once, you get stuck in the "while" loop forever no matter what the input is. Basically, "num" never stops being not 0.
You'd be better off using an if..else statement. Something like:
num = gets.chomp.to_i
if num != 0
if (num%2) == 0
puts 'yess'
else
puts 'nooo'
end
else
puts "that's 0, dude"
end
Integers have two methods for this. They are even? and odd?.
You can use this in your if statement as so:
if num.even?
puts 'yess'
else
puts 'nooo'
end
However, an easier way to write this is with ternary expressions:
puts num.even? ? "yes" : "no"
However, make sure num is an Integer. Anything coming from gets will be a String. So, you should be doing num = gets.chomp.to_i. Anything that is not a number, like "h", will return 0.
"5".to_i #=> 5
"h".to_i #=> 0
Related
I have to write a program which asks the user to enter a number.
The program keeps on asking the user for a number until the user types 'Stop'
at which point the sum of the numbers that the user has entered should be printed.
I've tried many,many things and none of my ideas work.
This is what I have - but I can that it isn't correct. What am I doing wrong?
I've only used while loops and arrays
total_user_input = []
# As long as the user inputs a number, the program will keep putting Give me a number
# and then adding that number to the total_user_input array.
puts "Give me a number: "
while user_input = gets.chomp.to_i
#add the input to the array total_user_input
total_user_input.push(user_input.to_i)
puts "Give me a number: "
# If the user however types stop, then the loop is broken and we jump down to the
# sum bit - where all of the numbers in the total_user_input array are added together
# and printed. End of program!
if user_input == "stop"
break
end
sum = 0
total_user_input.each { |num|
sum += num
}
puts sum
end
The output isn't as it should be.
As others have identified the problems with your code let me suggest how you might reorganize it. Ruby provides many ways to execute loops but you many find it desirable to primarily relay on the method Kernel#loop and the keyword break. (As you will learn in time, loop is particularly convenient when used with enumerators.)
def sum_numbers
tot = 0
loop do
print 'Gimme a number: '
s = gets.chomp
break if s == 'Stop'
tot += s.to_i
end
tot
end
The keyword break can optionally take an argument (though why that is not mentioned in the doc I cannot say), in which case it (if a literal) or its value (if a variable or method) is returned by loop. Here one would generally see
break tot if s == 'Stop'
without the final line, tot. As the loop returns tot and that is the last calculation performed by the method, the method will return the final value of tot.
You could have instead written
return tot if user_input == 'Stop'
but I think most coders believe best practice dictates that one should not return from a method from within a loop (or from within nested loops) unless there is a good reason for doing so.
Some small points:
I used print rather than puts to that the user's entry will be shown on the same line as the prompt.
I used s (for "string") rather than user_input because it reduces the chance of spelling mistakes (e.g., user_imput), speeds reading, and (possibly a foible of mine), looks neater. True, s is not descriptive, but one only has to remember its meaning for three consecutive lines of code. Others may disagree.
You could write, break if s.downcase == 'stop' if you want, say, 'stop' or 'STOP' to have the same effect as 'Stop'.
'23O3'.to_i #=> 23 (that's an an oh, not a zero), so in real life you'd want to confirm that either 'Stop' or the string representation of a number had been typed.
This is how I would do this preferring to use loop do end syntax with a break when it should. Also added a bit more text so user knows what's happening.
total_user_input = []
puts 'Give me a number or "stop" to end: '
loop do
user_input = gets.chomp
total_user_input << user_input.to_i
puts "Give me a number: "
break if user_input.downcase == "stop"
end
puts "Total entered: #{total_user_input.inject(&:+)}" unless total_user_input.empty?
puts 'goodbye!'
Note these few things:
get.chomp.to_i will convert every input to integer. ("stop" or any non integer string will be 0)
Arrangement of the flow is quite messy.
total_user_input = []
puts "Give me a number: "
while user_input = gets.chomp.strip
total_user_input.push(user_input.to_i)
sum = 0
total_user_input.each { |num|
sum += num
}
puts sum
if user_input == "stop"
break
end
end
Hope you understand this.
I'm trying to make users input a positive integer(>=1). If the user inputs a negative integer or 0, the program gonna notice and say you didn't put a valid integer, please try again. my program works so far until I try to input a string. My program break after I input a string. Does anybody know how to fix this?
I tried elsif !barsofsoap.match (/\A[-+]?[0-9]*.?[0-9]+\Z/)
puts "You didn't enter an integer, please put a positive integer", but it didn't work
loop do
puts "How many soaps are you looking to purchase? (Please put an integer)"
x = gets.chomp
barsofsoap = Integer(x) rescue false
if barsofsoap >= 1
break
else
puts "You didn't put an integer, please put an integer and try again."
end
end
I hope the program will not break if the user inputs a string.
The reason why your current code fails is because you use false as rescue value. You can't compare false >= 1. Sticking close to your original code you might wrap the comparison into a begin/end block.
loop do
puts "How many soaps are you looking to purchase? (Please put an integer)"
x = gets.chomp
begin
barsofsoap = Integer(x)
if barsofsoap >= 1
break
end
rescue ArgumentError => _error
puts "You didn't put an integer, please put an integer and try again."
end
end
Or simplifying the code:
loop do
puts "How many soaps are you looking to purchase? (Please put an integer)"
break if (barsofsoap = gets.to_i).positive?
puts "Invalid input. Provide a positive integer."
end
The above code doesn't detect if the input is a string or an integer. By replacing Integer(x) with x.to_i it would simply return 0 if invalid. Since you want the user to provide an positive integer it still requests them to provide a new integer.
nil.to_i #=> 0
''.to_i #=> 0
'asdf'.to_i #=> 0
'12.34'.to_i #=> 12
Like shown above the string '12.34' will produce the value 12. Depending on your requirements you might not want to use this value and instead mark it as invalid input. In this case you could use a regex to check the provided input.
loop do
puts "How many soaps are you looking to purchase? (Please put an integer)"
input = gets
break barsofsoap = input.to_i if input.match?(/\A[1-9]\d*\Z/)
puts "Invalid input. Provide a positive integer."
end
The regex /\A[1-9]\d*\Z/ will match the following:
\A Matches start of string.
[1-9] Matches one of the digits 1-9.
\d* Matches zero or more digits 0-9.
\Z Matches end of string. If the string ends with a newline, it matches just before the newline.
You try this: num.positive?
see here: https://ruby-doc.org/core-2.6/Numeric.html#method-i-positive-3F
Also you can try convert the text to an integer and validate by doing this:
num.is_a?(Integer)
https://ruby-doc.org/core-2.6/Object.html#method-i-is_a-3F
Or even better since input is always text, you can use a regex to make sure only numbers are entered: "12345" =~ /\A\d+\Z/
How about try this:
loop do
puts "How many soaps are you looking to purchase? (Please put an integer)"
barsofsoap = gets.chomp
if barsofsoap.match(/^[\d]+$/).nil?
puts "You didn't put an integer, please put an integer and try again."
elsif barsofsoap.to_i.positive?
break
else
puts "You didn't put an integer, please put an integer and try again."
end
end
Other option, using n.to_i.to_s == n to check the input is an Integer and moving the loop into a method:
def get_input_integer
loop do
puts "Enter a positive Integer"
n = gets.chomp
if n.to_i.to_s == n
return n.to_i if n.to_i.positive?
puts "It's not positive"
else
puts "It's not an integer"
end
end
end
x = get_input_integer
I have this loop:
puts "Welcome to the Loop Practice Problems"
puts " Write a number between 1 and 10, but not 5 or else...."
ans = gets.chomp!
if ans < 1
puts "Tf bruh bruh"
elsif ans > 10
puts "Now you just playin"
elsif x == 5
print "You wildin B"
else
puts "Fosho that's all I require"
end
It doesn't run properly, and I'm trying to understand why. If you can help me with this, I'd appreciate it.
If you know a good site for practice problems, I'd love to try it. I checked out Coderbyte and Code Kata, but the way they're set up doesn't look right, and they don't have questions to solve for fundamentals.
The issue here is that you're not converting ans to a number, but you're comparing it to one. ans is going to be a string.
In Ruby, when you compare a number to a string, Ruby says that the two aren't equal:
"1" == 1
=> false
You can reproduce the problem with this code:
puts "Welcome to the Loop Practice Problems"
puts " Write a number between 1 and 10, but not 5 or else...."
ans=gets.chomp!
p ans
The p method will output an "inspected" version of that object, (it's the same as doing puts ans.inspect). This will show it wrapped in quotes, which indicates that it's a string.
You probably want to do this:
ans = gets.chomp!.to_i
The to_i method here will convert the number to an integer, and then your comparisons will work correctly.
You have to convert input string type object into integer type
ans = gets.chomp!.to_i #input string convert into integer.
if ans < 1
puts "Tf bruh bruh"
elsif ans > 10
puts "Now you just playin"
elsif x == 5
print "You wildin B"
else
puts "Fosho that's all I require"
end
So my goal is to be able to run through a "while" loop and in each iteration create a new variable that includes the "iteration count" within that variables name and stores it for later use outside of the loop. See below for more details.
NOTE: The code is clearly wrong in so many ways but I'm writing it this way to make it more clear? as to what I am trying to accomplish. Thanks for any input on how this is possible.
count = "4"
while count > "0"
player"#{count}"_roll = rand(20)
puts 'Player "#{count}" rolled: "#{player"#{count}"_roll}"'
count -= 1
end
My goal is then to be able to access the variables that were created from within the loop at a later part of the program like so (more or less)
puts player4_roll
puts player3_roll
puts player2_roll
puts player1_roll
The key being that these variables were A) created in the loop B) With names relying on another variables input, and C) accessible outside the loop for later use.
Hopefully my question came out clear and any input will be greatly appreciated. I'm very new to programming and trying to get my head wrapped around some more complex ideas. I'm not sure if this is even possible to do in Ruby. Thanks!
I think the best way is to use arrays or hashes, with arrays its something like this:
count = 0
array = []
while count < 4 do
array[count] = rand(20)
puts "Player #{count} rolled: #{array[count]}"
count += 1
end
array.each do |var|
puts var
end
You store the result in the array and then you loop trough it. If you want the result of the second iteration of the loop you do something like this:
puts array[1]
If you want to use Hashes there are some modifications you need to do:
count = 0
hash = {}
while count < 4 do
hash["player#{count}_roll"] = rand(20)
puts "Player #{count} rolled: #{hash["player#{count}_roll"]}"
count += 1
end
hash.each do |key, var|
puts var
end
If you want the result of the second iteration of the loop you do something like this:
puts hash["player1_roll"]
You could set the variable using instance_variable_set and reference it that way
instance_variable_set("#player#{count}_roll", rand(20))
I am trying to write a small program that goes through an array's values outputting each individual value. When it reaches 15 it stops and outputs "too big".
Why is my logic below wrong, it makes sense to me..
x = [10,11,12,13,14,15,16,17,18]
def counting
for x[y]
while y < 15
puts y
else
puts "too big"
end
puts counting
I'm just learning sorry if this is a really simple solution.
That's nothing at all like Ruby syntax. You want a .each and a simple if statement:
x.each do |y|
if y < 15
puts y
else
puts "too big"
break
end
end
It appears though you are trying to use Ruby like you would a c-style programming language. It's possible and viable, albeit not recommended.
Code Blocks
Ruby has structure known as code blocks. Code blocks are sort of like anonymous functions.
You can read more about code blocks here.
x = [10,11,12,13,14,15,16,17,18]
# This is a code block.
x.each do |y| # The y between the '|'s is the parameter caught by the code block
if y < 15
puts y
else
puts "Too big."
break # Break out of the loop
end
end
If you want a one liner:
x.each {|y| y < 15 ? puts(y) : puts("too big") || break }
If you insist using while, it can be done as following:
i = 0
while i do
x[i] < 15 ? puts(x[i]) : puts("too big") || break
i+=1
end
I think the cleanest way to do this using while would be:
def counting(x)
i = 0
while x[i] < 15
puts x[i]
i += 1
end
puts 'too big'
end
counting([10,11,12,13,14,15,16,17,18])
Why is my logic below wrong, it makes sense to me..
Given that you program isn't even syntactically legal, it's impossible to tell what its semantics would be if it were syntactically legal, let alone why those semantics were wrong. However, here's an idiomatic Ruby solution (you will almost never use nor see while in any Ruby code, and you will certainly never see for):
puts x.take_while {|n| n < 15 }
puts 'too big'
I prefer writing in point-free style, however in this case the only way to do that is to make use of the symmetry of the condition and invert the order of operands, which will lead to awkward logic:
x.take_while(&15.method(:>))
Ao, in this case I would rather avoid point-free style, because it no longer matches the original specification literally. Instead of "take all numbers less than 15", we now have "take all numbers such that 15 is greater than those numbers", which reads awkward.