lvalue: Return or set lvalue attribute
Description
Return or set lvalue attribute
Usage
lvalue(x, ...)# S3 method for default
lvalue(x, ...)
lvalue(x, ...) <- value
# S3 method for default
lvalue(x, ...) <- value
Details
lvalue attribute is used by loss/risk function to return the loss value of
the function at a given point together with the function gradient