Rewrite Split to SubClause

src/rules.jl

@@ -1,30 +1,41 @@
 """
-    Split(splitpoint::SplitPoint, direction::Symbol) -> Split
-    Split(feature::Int, name::String, splitval::Float32, direction::Symbol) -> Split
+    SubClause
 
-A split in a tree.
-Each rule is based on one or more splits.
+A subclause denotes a conditional on one feature.
+Each rule contains a clause with one or more subclauses.
+For example, the rule `if X[i, 1] > 3 & X[i, 2] < 4, then ...` contains two subclauses.
 
-Data can be accessed via `_feature`, `_value`, `_feature_name`, `_direction`, and `_reverse`.
+A subclause is equivalent to a split in a decision tree.
+In other words, each rule is based on one or more splits.
+In pratice, a rule is based on at most two splits (has at most two subclauses).
+The reason for this is that rules with more than two subclauses will not end up
+in the final model, as is discussed in the original SIRUS paper.
+
+The data inside a `SubClause` can be accessed via
+
+- `_feature`,
+- `_feature_name`,
+- `_splitval`, and
+- `_direction`.
+
+To obtain the reverse, use `_reverse`.
 """
 struct SubClause
-    # Removed splitpoint
-    # splitpoint::SplitPoint
     feature::Int,
     feature_name::String,
     splitval::Float32,
     direction::Symbol # :L or :R
 end
 
-function Split(feature::Int, name::String, splitval::Float32, direction::Symbol)
-    return Split(SplitPoint(feature, splitval, name), direction)
-end
+_feature(s::SubClause) = s.feature
+_feature_name(s::SubClause) = s.feature_name
+_splitval(s::SubClause) = s.splitval
+_direction(s::SubClause) = s.direction
 
-_feature(split::Split) = _feature(split.splitpoint)
-_value(split::Split) = _value(split.splitpoint)
-_feature_name(split::Split) = _feature_name(split.splitpoint)
-_direction(split::Split) = split.direction
-_reverse(split::Split) = Split(split.splitpoint, split.direction == :L ? :R : :L)
+function _reverse(s::SubClause)
+    direction = s.direction == :L ? :R : :L
+    return SubClause(s.feature, s.feature_name, s.splitval, direction)
+end
 
 """
     TreePath(splits::Vector{Split}) -> TreePath