# Angle Identifier

**URL:** <https://www.ruby-forum.com/t/angle-identifier/194617>\
**Category:** Ruby\
**Created:** [September 8, 2010, 3:02am UTC](https://www.ruby-forum.com/t/angle-identifier/194617 "2010-09-08T03:02:37Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![humandictionary](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/65b543/32.png) [@humandictionary](https://www.ruby-forum.com/u/humandictionary)\
**Post date:** [September 8, 2010, 3:02am UTC](https://www.ruby-forum.com/t/angle-identifier/194617/1 "2010-09-08T03:02:37Z")

</div>

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?

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<div class="post-metadata">

**Author:** ![humandictionary](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/65b543/32.png) [@humandictionary](https://www.ruby-forum.com/u/humandictionary)\
**Post date:** [September 8, 2010, 5:59am UTC](https://www.ruby-forum.com/t/angle-identifier/194617/2 "2010-09-08T05:59:11Z")

</div>

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

Sounds like you could use some unit tests.

> **[Category: Test Frameworks - The Ruby Toolbox](https://www.ruby-toolbox.com/categories/testing_frameworks.html)**
>
> Explore and compare open source Ruby libraries

might help you get started.

---

<div class="post-metadata">

**Author:** ![humandictionary](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/h/65b543/32.png) [@humandictionary](https://www.ruby-forum.com/u/humandictionary)\
**Post date:** [September 8, 2010, 10:41am UTC](https://www.ruby-forum.com/t/angle-identifier/194617/3 "2010-09-08T10:41:01Z")

</div>

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  
ArgumentError: bad value for range  
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