On Apr 10, 12:23 pm, David Lee <[EMAIL PROTECTED]> wrote:
> A way to implement 'AND' and 'OR' conditional statements using hashes
>
> {:a => 1}.or(:b => 3)
> # => (a=1) OR (b=3)
>
> {:a => 1, :b => 3}
> # => (a=1) AND (b=3)
>
> {:a => 1}.and(:b => 3)
> # => {:a => 1, :b => 3}
> # => (a=1) AND (b=3)
>
> {:a => 1, :b => 3}.or{:a => 2}
> # => ((a=1) AND (b=3)) OR (a=2)
>
> Notice, that associativity is equal for and and or statements because
> ruby would evaluate left-to-right:
>
> {:a => 1}.or(:b => 3).and(:c => 4)
> # => ((a=1) OR (b=3)) AND (c=4)
>
> You can change that by surrounding grouped conditions with
> parentheses:
>
> {:a => 1}.and({:b => 2}.or(:b => 3).and(:c => 2))
> # => (a=1) AND ((b=2 OR b=3) AND c=2)
>
> The 'and' method can check for clashes:
>
> {:a => 2}.and(:a => 3)
> # => ERROR: column a has two clashing conditions
>
> {:a.gt => 2}.and(:a.gt => 3)
> # => ERROR: column a has two clashing conditions
>
> {:a.gt => 2}.and(:a.lt => 10)
> # => (a > 2) AND (a < 10)
>
> This can be implemented using ConditionAndGroup and ConditionOrGroup:
>
> Hash.and(Hash) => Hash # merged
>
> Hash.and(anything_else) => ConditionAndGroup
>
> Hash.or(anything) => ConditionOrGroup
>
> ConditionAndGroup.and(anything) => ConditionAndGroup
>
> ConditionOrGroup.and(anything) => ConditionAndGroup
>
> ConditionAndGroup.or(anything) => ConditionOrGroup
>
> ConditionOrGroup.or(anything) => ConditionOrGroup
I like this idea. Please try to work on an implementation if you have
time. If not, I'll try to do so at some point.
Jeremy
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