[julia-users] How to determine the type of a complex data structure

[Fred]

Hi,

I have a this kind of data structure :

type Ions_frag{}
  mz::Float64 
  intensity::Float64
  charge::Int64 
end


I read in performance tips that it is better to define the type of the data 
structure but I cannot find the good one for my data structure. I tried :

type Ions_frag{DataType}
  mz::Float64 
  intensity::Float64
  charge::Int64 
end


but it gives this error :

This may have arisen from a call to the constructor Ions_frag{DataType
}(...),
since type constructors fall back to convert methods.
Closest candidates are:
  call{T}(::Type{T}, ::Any)
  convert{T}(::Type{T}, !Matched::T)


Thank you for your comments !