Question on TimeGrid

[Javier Burroni]

Hello quantlib's developers.
I'm reading the TimeGrid code and I've noticed that the constructor of
this object using two iterator is not a particular case of the
constructor using two iterator plus a step parameter (set to zero),
and the object behaves different. Is there any reason to this?
Also, in the constructor wich use the end and a Step, the value 0.0 is
not set as the first mandatory time.
Just Curiosity
Cheers
/jb

ps: the use of this template oriented c++ you are using is awesome :)
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