On 3/23/2012 17:33, Nathan Rice wrote:
I will use "<=>" to mean "is equivalent to". That's not part of the DSL.
A flow has one or more streams:
1 stream:
[1,2,3]
2 streams:
[1,3,5] | [2,4,6]
Two flows can be concatenated:
[1,2,3] + [4,5,6]<=> [1,2,3,4,5,6]
[0] + ([1,2] | [3,4]) + [10]<=> [0,1,2,10] | [0,3,4,10]
([1,2] | [10,20]) + ([3,4] | [30,40])<=> [1,2,3,4] | [10,20,30,40]
Algebraically, your concatenation rules don't really make sense - your
flows are both distributive and non distributive.
?
You also make the
implicit assumption of an order over streams in a flow, but disregard
the implications of that assumption in some cases.
?
I understand what
you're trying to communicate, so I think you need to be a little more
strict and explicit in your definitions.
No, I don't think you understand what I meant.
A flow can be transformed:
[1,2] - f<=> [f(1),f(2)]
([1,2] | [3,4]) - f<=> [f(1,3),f(2,4)]
([1,2] | [3,4]) - [f]<=> [f(1),f(2)] | [f(3),f(4)]
([1,2] | [3,4]) - [f,g]<=> [f(1),f(2)] | [g(3),g(4)]
[1,2] - [f,g]<=> [f(1),f(2)] | [g(1),g(2)]
Given the examples you pose here, it is clear that you are assuming
that the streams are synchronized in discrete time. Since you do not
provide any mechanism for temporal alignment of streams you are also
assuming every stream will have an element at every time point, the
streams start at the same time and are of the same length. Is this
what you want?
Yes. I thought that streams as an alternative to functional programming
were widely known.
Some functions are special and almost any function can be made special:
[1,2,3,4,5] - filter(isprime)<=> [2,3,5]
[[],(1,2),[3,4,5]] - flatten<=> [1,2,3,4,5]
Note that 'filter' is not really necessary, thanks to 'flatten'.
This implies that your transformations again produce flows. You
should explicitly state this.
Isn't that obvious? BTW, those are not rigorous definitions. I thought I
was talking to people who regularly works with streams.
Flows can be named, remembered and used
as a value:
[1,2,3,4,5] - 'flow' + val('flow')<=> [1,2,3,4,5]*2
Is this a flow with two identical streams, or a flow with one long
stream formed by concatenation?
What does
[1,2,3,4,5]*2
mean in Python?
Those are Python's lists/arrays.
as a transformation chain:
[1,2,3] - skipfirst - 'again' | [4,5,6] - func('again')
<=> [2,3] | [5,6]
Recursion is also possible and stops when a function is applied to an empty
sequence.
Flows can be saved (push) and restored (pop) :
[1,2,3,4] - push - by(2) - 'double' - pop | val('double')
<=> [1,2,3,4] | [2,4,6,8]
There are easier ways to achieve the same result, of course:
[1,2,3,4] - [id, by(2)]
You are grasping at an algebra here, a sort of calculus of temporal
observations. You need to step back and make it rigorous before you
worry about issues such as a readable syntax.
Nathan
I don't agree. Sorry.
Kiuhnm
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