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package dstream
// GenerateFunc is a function that can be used to generate a new variable
// from existing variables. The first argument is a map from
// variable names to data (whose concrete types are slices held as
// empty interfaces). The second argument is a pre-allocated array (a
// slice provided as an interface{}) into which the new variable's
// values are to be written. Note that the destination array is not set to
// zeros before passing to the generate function.
type GenerateFunc func(map[string]interface{}, interface{})
type generate struct {
xform
gfunc GenerateFunc
newvarname string
dtype Dtype
}
// Generate appends a new variable to a Dstream, obtaining its values by
// applying the given function to the other variables in the Dstream.
// The new variable must not already exist in the Dstream.
func Generate(data Dstream, name string, fnc GenerateFunc, dtype Dtype) Dstream {
g := &generate{
xform: xform{
source: data,
},
newvarname: name,
gfunc: fnc,
dtype: dtype,
}
g.init()
return g
}
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