Simple program but so very stuck- Loops in Ruby - ruby

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.

Related

Check if integer is positive in ruby

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'm trying to design a simple Ruby calculator and I'm getting an error

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.

Generate largest number of 10 inputs

New to scripting here. Basically, I am needing to write a program to accept 10 input numbers and return the largest in the list.
I have this code, but obviously it is not running:
class Generator
def getNumbers
number = Array.new
puts "To begin, You will need to enter your numbers."
print "Press Enter to continue."
Console_Screen.pause
10.times do
print "\nPlease enter any number: "
input = STDIN.gets
input.chop!
list.push
return list
end
list.push(number)
print list.max
end
end
Console_Screen.new
Find = Generator.new
end
Can anyone help me with what I coded incorrectly?
There are many problems with your code. Among them I may point:
1) You created an array named number to store your numbers and then tried to push them to another variable named list;
2) As #tadman pointed, you used a return inside a times block and this makes the block to be executed only once;
3) You never invoked getNumbers to make your process really happen!
This code would do what you need:
class Generator
def get_numbers
numbers = Array.new
puts "To begin, You will need to enter your numbers."
puts
10.times do
print "\nPlease enter any number: "
input = STDIN.gets
input.chop!
numbers.push(input.to_i)
end
print numbers.max
end
end
Find = Generator.new
Find.get_numbers
Notice that I changed the name of your method from getNumbers to get_numbers, which is much more Ruby-like.
Notice that I also changed the name of your array from number to numbers, 'cause it will store numbers, not a single number. Naming your varables correctly may help you to think correctly about your problem. It also helps when it comes for other people reading your program. Even you, six months later, will have problems to understand your own code if you don't name things correctly an comment you code well.
By the way, I also pushed the numbers to numbers as integer, using #to_i. This will make the numbers be compared as numbers, not as strings. If you researsh a bit you'll find out this could be a bit different. If someone enters 0300 as a number, it will be considered to be smaller then 200 as string, but when converted to integers, they will be in the correct order.
Consider this approach perhaps:
#script.rb
nums = []
10.times do |c|
puts "enter number #{c+1}"
nums << gets.to_i
end
puts "max number is #{nums.max}"
Example
$ ruby script.rb
enter number 1
#5
enter number 2
#3
enter number 3
#66
enter number 4
#4
enter number 5
#3
enter number 6
#2
enter number 7
#1
enter number 8
#6
enter number 9
#9
enter number 10
#0
#max number is 66
I had the same assignment and this is what I ended up creating. (I had to get a little more involved with input control and I'm sure there's easier ways of doing this. Also had to utilize the variables as part of the grade. I assume to prevent me from ripping off the code above.)
class Screen
def cls
puts ("\n" * 25)
puts "\a"
end
def pause
STDIN.gets
end
end
Console_Screen = Screen.new
num = [] #array to store user input
$counter = 1
loop do
puts "Please enter number " + $counter.to_s + " of a series of 10 numbers in order to determine the largest."
# Console_Screen.pause
loop do
print "Enter Number Here:"
number = gets.chomp
num << number.to_i if number =~ /[0-9]/ #only writes to the array if it's a number
break if number =~ /[0-9]/ #only allow numbers
end
$counter += 1
break if $counter == 11
end
puts "Press Enter to have your numbers sorted and the largest presented to you."
Console_Screen.pause
largest = num.max
puts "This is your largest number: " + largest.to_s
Console_Screen.pause

How to run a simple Ruby script

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

Misbehaving Case Statement

I'm messing around in Ruby some more. I have a file containing a class with two methods and the following code:
if __FILE__ == $0
seq = NumericSequence.new
puts "\n1. Fibonacci Sequence"
puts "\n2. Pascal\'s Triangle"
puts "\nEnter your selection: "
choice = gets
puts "\nExcellent choice."
choice = case
when 1
puts "\n\nHow many fibonacci numbers would you like? "
limit = gets.to_i
seq.fibo(limit) { |x| puts "Fibonacci number: #{x}\n" }
when 2
puts "\n\nHow many rows of Pascal's Triangle would you like?"
n = gets.to_i
(0..n).each {|num| seq.pascal_triangle_row(num) \
{|row| puts "#{row} "}; puts "\n"}
end
end
How come if I run the code and supply option 2, it still runs the first case?
Your case syntax is wrong. Should be like this:
case choice
when '1'
some code
when '2'
some other code
end
Take a look here.
You also need to compare your variable against strings, as gets reads and returns user input as a string.
Your bug is this: choice = case should be case choice.
You're providing a case statement with no "default" object, so the first clause, when 1, always returns true.
Effectively, you've written: choice = if 1 then ... elsif 2 then ... end
And, as Mladen mentioned, compare strings to strings or convert to int: choice = gets.to_i

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