Ruby math parenthesis wierdness

[Tom Verbeure]

All,

The code below:

m = 5*(
(1.0)
- (1.0/2.0)
)
puts m
m = 5*(
(1.0) - (1.0/2.0)
)
puts m

prints out:

bash-3.2$ ./run.rb
-2.5
2.5

The second result is what I expect, but I don't understand the first
result.

I usually put operands at the end of the line instead of the
beginning, so I never ran into this before, but this was originally
Python code that I converted into ruby.

Any insights?

Thanks,
Tom

 

[Gregg Kang]

I'm getting this type of issue too. It looks like any number you put
after the first paren '(' is ignored.

All these examples produce -20

m = 10*(123
-2)
puts m

 

[Mikael Høilund]

All,

The code below:

m =3D 5*(
(1.0)

This is the cause of the unexpected behavior. =46rom what I can see, =20
Ruby is interpreting the newline after (1.0) as a statement separator. =20=

Compare:

puts 5*(
(1.0);
- (1.0/2.0)
)

What's actually happening is that the third line (- (1.0/2.0)) is seen =20=

as a separate statement, not as a continuation on the second line. The =20=

minus sign in the beginning of the line is interpreted as the unary =20
negation operator, not the binary (as in relating to two numbers, not =20=

one) subtraction operator.

This works, however:

puts 5*(
(1.0) -
(1.0/2.0)
)

A quick irb session also illustrates my point:
?> 1.0/2.0

The fact that the last prompt is "?>", not ">>" is the key point here.

Hope this helps
Mikael H=F8ilund

 

[Gregg Kang]

I see. Thanks Phlip!

 

[Tom Verbeure]

Hope this helps

Yes, definitely.

Thanks All!
Tom

 

[Dave Bass]

If you make the line continuations explicit by adding backslashes, Ruby
gives the correct answer:

irb(main):005:0> m = 5*( \
irb(main):006:1* (1.0) \
irb(main):007:1* - (1.0/2.0) \
irb(main):008:1* )
=> 2.5