Programming a basic calculator in Ruby - ruby

Question

This is my first foray into computer programming. I have chosen to learn Ruby, and I am enjoying it quite a bit. However, I am a little confused as to why the answer will not output properly in this bit of code.
def addition_function
puts "Which numbers would you like to add?"
#n1 = gets.chomp
#n2 = gets.chomp
#n1 + #n2 == #answer
puts "The sum is... #{#answer}"
end
def subtraction_function
puts "Which numbers would you like to subtract?"
#n1 = gets.chomp.to_i
#n2 = gets.chomp.to_i
#n1 - #n2 == #answer
puts "The answer is... #{#answer}"
end
def multiplication_function
puts "Which numbers would you like to multiply?"
#n1 = gets.chomp
#n2 = gets.chomp
#n1 * #n2 == #answer
puts "The answer is... #{#answer}"
end
puts "Would you like to [add], [multiply], or [subtract]?"
response = gets.chomp
if response == "add" then
addition_function
end
if response == "subtract" then
subtraction_function
end
if response == "multiply" then
multiplication_function
end
I know this is probably horrible code... but could someone help steer me in the right direction?

Answer 1

Consider this code:
def get_int_values
[gets, gets].map{ |s| s.chomp.to_i }
end
puts "Would you like to [add], [multiply], or [subtract]?"
response = gets.chomp
case response.downcase
when 'add'
puts "Which numbers would you like to add?"
operator = :+
when 'subtract'
puts "Which numbers would you like to subtract?"
operator = :-
when 'multiply'
puts "Which numbers would you like to multiply?"
operator = :*
end
answer = get_int_values.inject(operator)
puts "The answer is... #{ answer }"
The idea is to follow the "DRY" principle: "DRY" means "Don't Repeat Yourself", which the vast majority of the time, is a really good thing.
To help avoid typing mistakes I'd recommend doing something like:
puts "Would you like to [a]dd, [m]ultiply, or [s]ubtract?"
response = gets.chomp
case response[0].downcase
then change the when clauses to match the first letter of the desired operation.
Which will work unless response is empty. You can figure out how to handle that.
another way to obtain answer, once operator is determined, is answer = gets.to_i.send(operator, gets.to_i)
That's true, but here's why I refactored the code the way I did: If, for some reason, there was a need to operate on more than two values, only one thing has to be changed:
[gets, gets].map{ |s| s.chomp.to_i }
could become:
[gets, gets, gets].map{ |s| s.chomp.to_i }
Or, better, could be transformed to something like:
def get_int_values(n)
n.times.map { gets.chomp.to_i }
end
Nothing else will have to change except to find out how many values are needed.
Now, to do it all right would require different text to alert the user that multiple values are expected, but that's easily done by letting letting the user say how many they want to enter, and then prompting for each gets:
def get_int_values(n)
n.times.map.with_index { |n|
print "Enter value ##{ 1 + n }: "
gets.chomp.to_i
}
end
puts "Would you like to [add], [multiply], or [subtract]?"
response = gets.chomp
puts "How many values?"
num_of_values = gets.to_i
case response.downcase
when 'add'
puts "Which numbers would you like to add?"
operator = :+
when 'subtract'
puts "Which numbers would you like to subtract?"
operator = :-
when 'multiply'
puts "Which numbers would you like to multiply?"
operator = :*
end
answer = get_int_values(num_of_values).inject(operator)
puts "The answer is... #{ answer }"
inject can scale up easily because it doesn't presuppose knowledge about the number of values being operated on.
I think with_index in n.times.map.with_index is an artifact you forgot to delete.
It was deliberate but I like this better:
def get_int_values(n)
1.upto(n).map { |n|
print "Enter value ##{ n }: "
gets.chomp.to_i
}
end

Answer 2

Your assignments are on the wrong side of the statement. You should have answer = n1 * n2,
which is not the same as answer == n1 * n2 (this is a check for equality, using ==). The expression always goes on the right, and the variable the result is assigned to goes on the left -- this is pretty much universal, but not necessarily intuitive coming from algebra.
Also: using an # prior to a variable name differentiates it as an instance variable, or member, of a class. From what you've shown here you don't need to include those, just normally scoped variables are required for this use.
Check out this question for more on that part.

Answer 3

The "#" sigil is used to indicate a class instance variable, you have no class so don't use it.
#n1 + #n2 == #answer
Is a boolean expression evaluating whether #n1 + #n2 is equal to #answer.
It will evaluate to true or false.... but you don't make use of the answer.
What you want is ...
answer = n1 + n2
I strongly recommend you always run Ruby with the -w option. It will save you much much heartache.
Please indent your "end"'s to match your "def" (or "if").
You repeat n1 = gets.chomp.to_i all over the place, do it once and pass the answers as a parameter...
response = gets.chomp
n1 = gets.chomp.to_i
n2 = gets.chomp.to_i
if response == "add" then
addition_function( n1, n2)
elsif...

Answer 4

A few suggestions not mentioned by others:
Shorten your method (not "function") names and use verbs (e.g., add instead of addition_method).
As well as using local variables rather than instance variables (mentioned by others), eliminate them where you can. For example, you could simplify
.
def add
puts "Which numbers would you like to add?"
n1 = gets.to_i
n2 = gets.to_i
answer = n1 + n2
puts "The sum is... #{answer}"
end
to
def add
puts "Which numbers would you like to add?"
puts "The sum is... #{gets.to_i + gets.to_i}"
end
Notice I've used the Ruby convention of indenting two spaces.
You don't need chomp here (though it does no harm), because "123followed by \n or any other non-digits".to_i => 123.
A case statement would work well at the end (and let's loop until the user chooses to quit):
.
loop do
puts "Would you like to [add], [multiply], [subtract] or [quit]?"
case gets.chomp
when "add"
add
when "subtract"
subtract
when "multiply"
multiply
when "quit"
break
end
or just
def quit() break end
loop do
puts "Would you like to [add], [multiply], [subtract] or [quit]?"
send(gets.chomp)
end
Here we do need chomp. You could replace loop do with while true do or use other equivalent constructs.

Answer 5

class Calculator
def Calc
puts"==well come to mobiloitte calculator=="
puts "enter the first operand:"
#op1 = gets.chomp
return if #op1=="q"
#o1=#op1.to_i
puts "entre the second operand:"
#op2 = gets.chomp
return if #op2=="q"
#o2=#op2.to_i
strong text puts "enter any one operator of your choice (add,sub,mul,div,mod)"
operator = gets.chomp
case operator
when 'add' then #s=#o1+#o2 ; puts "\n ##o1 + ##o2 =##s"
when 'sub' then #t=#o1-#o2 ; puts "\n ##o1 - ##o2 =##t"
when 'mul' then #l=#o1*#o2 ; puts "\n ##o1 * ##o2 =##l"
when 'div' then #r=#o1/#o2 ; puts "\n ##o1 \ ##o2 =##r"
when 'md' then #d=#o1%#o2 ; puts "\n ##o1 % ##o2 =##d"
else
puts"invalide input"
end
end
end
obj= Calculator.new
$f=obj.Calc

Answer 6

You are using #n1 + #n2 == #answer to try and set the answer. What you want to do is #answer = #n1 + #n2.
= is assignment, == is a comparison operator.
Also, you will need to #n1 = gets.chomp.to_i. This will convert your input to an integer from a string. Do that with #n2 as well.
You also do not need to use the # before each of your variables. That should only be used when you are dealing with classes, which you do not appear to be doing.

Answer 7

print "enter number 1 : "
n1 = gets.chomp.to_f
print "enter number 2 : "
n2 = gets.chomp.to_f
print "enter operator: "
op = gets.chomp
if op == '+'
puts "#{n1} + #{n2} = #{n1 + n2}"
elsif op == '-'
puts "#{n1} - #{n2} = #{n1 - n2}"
elsif op == '*'
puts "#{n1} * #{n2} = #{n1 * n2}"
elsif op == '/'
puts "#{n1} / #{n2} = #{n1 / n2}"
end

Answer 8

puts "Would you like to
0 ---- [exit],
1 ---- [add],
2 ---- [subtract],
3 ---- [multiply],
4 ---- [divide]"
response = gets.chomp
case response.downcase
when '1'
def addition_function
puts "Which numbers would you like to add?"
n1 = gets.to_i
n2 = gets.to_i
answer = n1 + n2
puts "The sum is... #{n1} + #{n2} = #{answer}"
end
addition_function()
#Subtract
when '2'
def subtraction_function
puts "Which numbers would you like to subtact?"
n1 = gets.to_i
n2 = gets.to_i
answer = n1 - n2
puts "The subtraction is... #{n1} - #{n2} = #{answer}"
end
subtraction_function()
#Multiply
when '3'
def multiplication_function
puts "Which numbers would you like to multiply?"
n1 = gets.to_i
n2 = gets.to_i
answer = n1 * n2
puts "The multiplication is... #{n1} * #{n2} = #{answer}"
end
multiplication_function()
#Division
when '4'
def division_function
puts "Which numbers would you like to divide?"
n1 = gets.to_i
n2 = gets.to_i
answer = n1 / n2
puts "The division is... #{n1} / #{n2} = #{answer}"
end
division_function()
else '0'
puts "Exit! Thank You for using us!"
end

Answer 9

#ruby script to do the calculator
puts " enter the number1"
in1=gets.to_i
puts " enter the number2"
in2=gets.to_i
puts "enter the operator"
op=gets.chomp
case op
when '+'
plus=in1+in2
puts "#{in1+in2}"
#puts "#{plus}"
when '-'
min=in1-in2
puts "#{min}"
when '*'
mul= in1*in2
puts "#{mul}"
when '/'
div=in1/in2
puts "#{div}"
else
puts "invalid operator"
end

Answer 10

begin
puts 'First number:'
a = $stdin.gets.chomp.to_i
puts 'Second number:'
b = $stdin.gets.chomp.to_i
operation = nil
unless ['+', '-', '*', '/', '**'].include?(operation)
puts 'Choose operation: (+ - * /):'
operation = $stdin.gets.chomp
end
result = nil
success = false
case operation
when '+'
result = (a + b).to_s
when '-'
result = (a - b).to_s
when '*'
result = (a * b).to_s
when '/'
result = (a / b).to_s
when '**'
result = (a**b).to_s
else
puts 'There is not such kind of operation'
end
success = true
puts "Результат: #{result}"
rescue ZeroDivisionError => e
puts "You tried to devide number by zero! Error: #{e.message}"
end
if success
puts "\nSuccess!"
else
puts "\nSomething goes wrong :("
end

Answer 11

puts ("plz enter a number :")
num1 = gets.chomp.to_f
puts ("plz enter a another number")
num2 = gets.chomp.to_f
puts ("plz enter the operation + , - , x , / ")
opp = gets.chomp
if opp == "+"
puts (num1 + num2)
elsif opp == "-"
puts (num1 - num2)
elsif opp == "x"
puts (num1 * num2)
elsif opp == "/"
puts (num1 / num2)
else puts ("try again :|")
end