Reactive getindex hack

update_asset.jl

julia> using Grist  #brings in Reactive and other experimental packages

julia> res
10-element Array{Timestamps.Timestamp{T},1}:
 2000-01-03 |  200      Stock           95.0  $    AAPL
 2000-03-15 | -100      Stock         116.25  $    AAPL
 2000-05-25 |  100      Stock          87.27  $    AAPL
 2000-08-07 | -100      Stock          47.94  $    AAPL
 2000-10-17 |  100      Stock          20.12  $    AAPL
 2000-12-28 | -100      Stock          14.81  $    AAPL
 2001-03-13 |  100      Stock          19.56  $    AAPL
 2001-05-23 | -100      Stock          23.23  $    AAPL
 2001-08-03 |  100      Stock           19.5  $    AAPL
 2001-10-19 | -100      Stock           18.3  $    AAPL

julia>  A = Input(res[1].value)
ticker:         AAPL
basis:          111.94
quantity:       100
currency:       USD
tick:           0.01
multiplier:     1.0
id:             NA

julia> A.value.basis = 100; # make mental math easier

julia> A
ticker:         AAPL
basis:          100.0
quantity:       100
currency:       USD
tick:           0.01
multiplier:     1.0
id:             NA

julia> buysome = Input((100,90.00))
(100,90.0)

julia> function Base.getindex{T<:Input}(I::T, n::Int64)
       Input(I.value[n])
       end
getindex (generic function with 172 methods)

julia> bot_some = lift((fa, qty, fill) -> transact(fa,qty,fill), A, buysome[1], buysome[2])
200

julia> A
ticker:         AAPL
basis:          95.0
quantity:       200
currency:       USD
tick:           0.01
multiplier:     1.0
id:             NA

@shashi provided this solution

julia> initial_buy = (100,90.00)
(100,90.0)
julia> buysome = Input(initial_buy)
(100,90.0)
julia> bot_some = lift(A, buysome) do fa, buy
    qty, fill = buy
    transact(fa,qty,fill)
end