Factorial in Ruby - ruby

Question

I'm trying to do in the Ruby program the summation of a factorial. and I can not solve. a clarification, when they run out points .... means that the logic is fine. if you get a F in one of the points, it means that the logic is wrong.
Write a program to calculate the sum of 1 + 1 / (2!) + 1 / (3!) + 1 / (4!) + .... + 1 / (n!) For a given n. Write the program in two ways: using While, For
def factorial(n)
#(n == 0) ? 1 : n * factorial(n - 1)
fact = 1
for i in 1..n
fact = fact * i
end
return fact
end
def sumatoriaWhile(n)
total = n
sumatoria = 0.0
while n > 1
total = total * (n - 1)
n = n - 1
sumatoria =sumatoria + total.to_f
end
return (1 + (1 / total.to_f)).round(2)
end
def sumatoriaFor(n)
fact = 1
sumatoria = 0.0
for i in 1..n
for j in 1..i
fact = fact * j
end
sumatoria = sumatoria + (1 / fact.to_f)
i = i + 1
end
return sumatoria.round(2)
end
#--- zona de test ----
def test_factorial
print validate(120, factorial(5))
print validate(5040, factorial(7))
print validate(362880, factorial(9))
end
def test_sumatoriaWhile
print validate(1.50, sumatoriaWhile(2))
print validate(1.83, sumatoriaWhile(3))
end
def test_sumatoriaFor
print validate(1.50, sumatoriaFor(2))
print validate(1.83, sumatoriaFor(3))
end
def validate (expected, value)
expected == value ? "." : "F"
end
def test
puts "Test program"
puts "---------------------------"
test_factorial
test_sumatoriaWhile
test_sumatoriaFor
puts " "
end
test

Answer 1

My friend, Thank you for your prompt response. First of all, I appreciate the help given. I am learning ruby programming and want to learn more as you and the other people. if indeed the answer is wrong. I have modified the answer. and also need to know what the function of While. and I hereby amended program again. and now I get an F on the part of WHILE.
def factorial(n)
fact = 1
for i in 1..n
fact = fact * i
end
return fact
end
def sumatoriaWhile(n)
total = n
sumatoria = 0.0
while n < 1
total = total * (n - 1)
sumatoria = sumatoria + (1.0 / total.to_f)
n = n - 1
end
return sumatoria.round(2)
end
def sumatoriaFor(n)
fact = 1
sumatoria = 0.0
for i in 1..n
fact = fact * i
sumatoria = sumatoria + (1.0 / fact.to_f)
end
return sumatoria.round(2)
end
#--- zona de test ----
def test_factorial
print validate(120, factorial(5))
print validate(5040, factorial(7))
print validate(362880, factorial(9))
end
def test_sumatoriaWhile
print validate(1.50, sumatoriaWhile(2))
print validate(1.67, sumatoriaWhile(3))
end
def test_sumatoriaFor
print validate(1.50, sumatoriaFor(2))
print validate(1.67, sumatoriaFor(3))
end
def validate (expected, value)
expected == value ? "." : "F"
end
def test
puts "Test de prueba del programa"
puts "---------------------------"
test_factorial
test_sumatoriaWhile
test_sumatoriaFor
puts " "
end
test

Answer 2

I have a hard time figuring out what you're doing in the summation function. Here's a straightforward function:
def sumatoriaFor(n)
return 0 if n <= 0
factorial = 1
sum = 0.0
for i in 1..n
factorial *= i
sum += 1.0 / factorial.to_f
end
return sum.round(2)
end
def sumatoriaWhile(n)
return 0 if n <= 0
i = 1
factorial = 1
sumatoria = 0.0
while i <= n
factorial *= i
sumatoria += (1.0 / factorial.to_f)
i = i + 1
end
return sumatoria.round(2)
end
The while look is straight forward too now. Also your validation is wrong:
1 + 1/2 + 1/6 ~= 1 + 0.5 + 0.17 = 1.67