Conditionally use greater than or less than

Ruby
1

what is the best way to do this in ruby?

if condition
then do a whole bunch of comparisons using >
else
do all the same comparisons except using <

2

I ended up doing something like this:

def threshold_compare(value1, value2, operation)
if operation == ‘>=’
value1 >= value2
elsif operation == ‘<=’
value1 <= value2
end
end

3

On 12/04/12 16:29, phil rosenstein wrote:

I ended up doing something like this:

def threshold_compare(value1, value2, operation)
if operation == ‘>=’
value1>= value2
elsif operation == ‘<=’
value1<= value2
end
end

What about just

1.9.2p290 :001 > def threshold_compare(value1, value2, operator=’==’)
1.9.2p290 :002?> value1.send(operator.to_sym, value2)
1.9.2p290 :003?> end

Additionally you could add a check for valid operators and see if value1
responds to the method if you wanted. Something like

if [:==, :>, :<, :>=, :<=].include? operator.to_sym &&
value1.respond_to? operator.to_sym

… and maybe raise an ArgumentError with a helpful message if the
conditions aren’t met.

You might not need to be paranoid about it depending on your context.
You could also ‘bake’ the valid operators array into a variable
somewhere to cut some overhead.

Sam

4

Hi,

You can use the generalized comparision operator <=>, which returns -1,
0 or 1 depending on the order of the operands. If you set the result for
the operation, you can force it to either do “>” comparisons or “<”
comparisons:

comparison_result =
condition ? 1 : -1

comparisons: if condition is true, then a <=> b == comparison_result

means a > b, otherwise it means a < b

1 <=> 3 == comparison_result
4 <=> 2 == comparison_result

However, the “send” solution is probably easier to understand:

compare =
condition ? :> : :<

1.send compare, 3
4.send compare, 2