How to understand objects, methods and arguments in Ruby calculations

Question

While learning Ruby gotchas, I am getting different results with some calculations in IRB:

1-2-7-2 # => -10

1.-2.-7.-2 # => 4

1.-2.-7.-2.-4 # => 8

1.-2.-7.-2.+4 # => 0

1.-(2).-(7).-(2) # => -10

Possibly it is related to methods and arguments? I am trying to wrap my head around this.

Answer 1

You've chosen an interesting way to approach calculations.

I guess you are trying to omit zeros in your expression 1.-2.-7.-2 which will return -10 if you write it as 1.0 - 2.0 - 7.0 - 2 .

The way you're getting 4 is because 1.- construction calls -() method because everything is an object in Ruby and then you pass an argument to the function.

In your case it will be parsed as

1.-( 2.-( 7.-(2) ) )

# if we try to unwrap
a = 7.-(2) # => 5
b = 2.-(a) # => -3
1.-(-3) # (or 1 + 3) => 4