calculate fibonacci sequence position from user inserted value - ruby

Question

Below is my full program's code:
GradeAvg = [[59, 'F'], [69, 'D'], [79, 'C'], [89, 'B'], [100, 'A']]
def letter_grade
num = number_grade
_, letter = GradeAvg.find { |n, _| num <= n }
[num, letter]
end
def number_grade
loop do
puts 'Please insert a number between 1 and 100.'
num = gets.to_i
break(num) if (1..100).cover?(num)
end
end
def fib(n)
return n if n < 2
fib(n-1) + fib(n-2)
end
10.times { print letter_grade; (num).each { |n| puts fib(n) }; puts }
It is failing with the below error:
undefined local variable or method `num' for main:Object (NameError)
Why can't I apply my fibonacci sequence calculation on my acceptable user inserted value in variable num?

Answer 1

You're trying to access num which is assigned in letter_grade. You must use the return value of the function call (ie num, letter = letter_grade) to read the result.
It should also be noted that Fixnum#each (ie (num).each) is not a method. 10.times { ... } already makes a loop though, so I think this was just an oversight on your part.
See the bolded section for changes. I also changed your fibonacci function to calculate in linear time (instead of exponential time)
GradeAvg = [[59, 'F'], [69, 'D'], [79, 'C'], [89, 'B'], [100, 'A']]
def number_grade
loop do
print "Please insert a number between 1 and 100."
num = gets.to_i
break(num) if (1..100).cover?(num)
end
end
def letter_grade
num = number_grade
_, letter = GradeAvg.find { |n, _| num <= n }
[num, letter]
end
def fib (n, a = 0, b = 1)
if n == 0 then
a
else
fib n - 1, b, a + b
end
end
10.times do
num, letter = letter_grade
puts letter
puts (fib num)
end
Example program execution
# Please insert a number between 1 and 100. 95
# A
# 31940434634990099905
# Please insert a number between 1 and 100. 87
# B
# 679891637638612258
# Please insert a number between 1 and 100. 77
# C
# 5527939700884757
# Please insert a number between 1 and 100. 66
# D
# 27777890035288
# Please insert a number between 1 and 100. 55
# F
# 139583862445
# Please insert a number between 1 and 100. 10
# F
# 55
# Please insert a number between 1 and 100. ...
# ...

Answer 2

Try like this:
GradeAvg = [[59, 'F'], [69, 'D'], [79, 'C'], [89, 'B'], [100, 'A']]
def letter_grade
#num = number_grade
_, letter = GradeAvg.find { |n, _| #num <= n }
[#num, letter]
end
def number_grade
loop do
puts 'Please insert a number between 1 and 100.'
#num = gets.to_i
break(#num) if (1..100).cover?(#num)
end
end
def fib(n)
return n if n < 2
fib(n-1) + fib(n-2)
end
10.times { print letter_grade; puts fib(#num)}