How to check if input is an integer?- Ruby [duplicate] - ruby

Question

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How to test if a string is basically an integer in quotes using Ruby
(19 answers)
Closed 6 years ago.
I have this code where I am entering input for sides of a triangle. Depending on the values, it will print it the triangle is equilateral, isoceles, or scalene. It's executing for number values, but how do I specify that the input should only be integers? For example, if I type in "w" , it should say invalid or error, but in this case, it executes. How do I solve this?
Basically, I am looking for a way to write that if a string were to be inputted, it should show up as an error (then I would write a print statement saying it is invalid). So could I put that into another if statement? (before the ones mentioned below)
Example Code:
puts "Enter the triangle length"
x = gets.chomp
puts "Enter the triangle width"
y = gets.chomp
puts "Enter the triangle height"
z = gets.chomp
if x == y and y == z
puts "This triangle is equilateral"
else if
x==y or y == z or x==z
puts "This triangle is isoceles"
else if
x!=y and y!=z and x!=z
puts "this triangle is scalene"
end
end
end

Answer 1

If you are dealing with integers, you can check this with ruby.
Note, this is not as robust as regex, but it covers most cases.
if (input != '0') && (input.to_i.to_s != input.strip)
# input is not a number
else
# input is a number
end
strip is there if you want to accept input with leading or trailing whitespace, otherwise you can leave it off.

Answer 2

While all the other answers are probably more or less robust, I would go with another one. Since you have a triangle sides lengths, they are to be greater than zero, right? Then one might use the side effect of String#to_i method: for everything that is not converting to integer it returns zero. Therefore:
x = gets.chomp.to_i
y = gets.chomp.to_i
z = gets.chomp.to_i
raise "Wrong input" unless x > 0 && y > 0 && z > 0
# ...

Answer 3

You can do something like this:
x = x.to_i
puts "Please enter an integer" if x == 0
Why?
Because:
"ABC".to_i # returns 0
You may be better off calling strip instead of chomp
gets.strip.to_i
An example:
## ruby user_age.rb
# input variables
name = ""
years = 0
MONTHS_PER_YEAR = 12 # a constant
# output variable
months = 0
# processing
print "What is your name? "
name = gets.strip
print "How many years old are you? "
years = gets.strip.to_i
puts "please enter an integer" if years == 0
months = years * MONTHS_PER_YEAR
puts "#{name}, at #{years} years old, "\
"you are #{months} months old."

Answer 4

There are several ways of doing it. If you allow for a leading sign,
x =~ /^[+-]?\d+$/
would be a possibility.
You will also have to think whether or not you allow surrounding or embedding spaces (for instance, a space between the sign and the first digit).

Answer 5

I assume that any string value that, when converted to a float, equals an integer is to be accepted and the integer value is to be returned. Moreover, I assume integers can be entered with the "xen" (or "xEn") notation, where x is an integer or float and n is an integer.
def integer(str)
x = Float(str) rescue nil
return nil if x==nil || x%1 > 0
x.to_i
end
integer("3") #=> 3
integer("-3") #=> -3
integer("3.0") #=> 3
integer("3.1") #=> nil
integer("9lives") #=> nil
integer("3e2") #=> 300
integer("-3.1e4") #=> -31000
integer("-30e-1") #=> -3
integer("3.0e-1") #=> nil

Answer 6

You could use Integer() to check if a string contains an integer:
Integer('1234')
#=> 1234
Integer('foo')
#=> ArgumentError: invalid value for Integer()
This could be combined with a retry:
begin
number = Integer(gets) rescue retry
end