.generic_selector(variable_column, select_column, select_expr, fun_name).is_selector_scoped(variable_column, select_column)
custom selector functions
string indicating column variable names are stored
character vector of columns used in the select_expr=
argument
unquoted predicate command to subset a data frame to select variables
quoted name of function where .generic_selector()
is being used.
This helps with error messaging.
.is_selector_scoped()
checks if a selector has been properly registered
in env_variable_type$df_var_info
.