# Angle Identifier

puts “Enter degree of angle:”
measure = gets.chomp.to_i
if measure == “180”.to_i then puts “That’s a straight angle.”
if measure == 181…359.to_i then puts “That’s an obtuse angle.”
if measure == 91…179.to_i then puts “That’s an obtuse angle.”
if measure == “90”.to_i then puts “That’s a right angle.”
if measure < 90.to_i then puts “That’s an acute angle.”
if measure == “360”.to_i then puts “That’s a circle…”
else puts “That’s an invalid measurement.”
end
end
end
end
end
end

This seems like it should work, but sometimes it doesn’t. Help?

This seems like it should work, but sometimes it doesn’t. Help?

Sounds like you could use some unit tests.

Hd Pwnz0r wrote:

puts “Enter degree of angle:”
measure = gets.chomp.to_i
if measure == “180”.to_i then puts “That’s a straight angle.”
if measure == 181…359.to_i then puts “That’s an obtuse angle.”

That won’t work; consider the case when measure is 190, does 190 ==
181…359 ?

The way to find out is by testing your code interactively in irb.

irb(main):001:0> measure = 190
=> 190
irb(main):002:0> measure == 181…359
from (irb):2
irb(main):003:0> measure == (181…359)
=> false

The first error is because the line was parsed as (measure == 181)…359,
that is (false…359), which is not a valid range.

After adding the right parentheses, you can see that the Fixnum object
190 is not equal to the Range object 181…359. You need a different
test to see if 190 is within the proscribed range.

Here are a few options to consider:

if measure == 180

elsif (181…359).include?(measure)

elsif 91 <= measure && measure <= 179

end

Or more simply, reorder your tests:

if measure < 90

elsif measure == 90

elsif measure < 180

elsif measure == 180

elsif measure < 360

end

That also has the advantage of working with floating point values like
180.5 which wouldn’t be accepted by your original test for 181…359.

If you want to work with Ranges, there is a neat solution using the case
statement:

case measure
when 180

when 181…359

when 91…179

end

This expands to:

if 180 === measure

elsif 181…359 === measure

elsif 91…179 === measure

end

Helpfully, the ‘===’ operator on an integer checks for equality, but the
‘===’ operator on a range checks for inclusion.

irb(main):005:0> (181…359).include? 190
=> true
irb(main):006:0> (181…359) === 190
=> true

There is also the three dot form of range: x…y means “from x up to but
not including y”.

case measure
when 180

when 180…360

when 90

when 90…180

when 0…90

end

irb(main):007:0> (180…360).include? 359
=> true
irb(main):008:0> (180…360).include? 359.999
=> true
irb(main):009:0> (180…360).include? 360
=> false