LeafCount

expreduce/builtin_expression.go

@@ -29,6 +29,17 @@ func flattenExpr(src *Expression, dst *Expression, level int64, cl *CASLogger) {
 	}
 }
 
+func leafCount(e Ex) int64 {
+	if asExpr, isExpr := e.(*Expression); isExpr {
+		res := int64(0)
+		for _, part := range asExpr.Parts {
+			res += leafCount(part)
+		}
+		return res
+	}
+	return 1
+}
+
 func GetExpressionDefinitions() (defs []Definition) {
 	defs = append(defs, Definition{
 		Name: "Head",
@@ -131,6 +142,15 @@ func GetExpressionDefinitions() (defs []Definition) {
 			return dst
 		},
 	})
+	defs = append(defs, Definition{
+		Name: "LeafCount",
+		legacyEvalFn: func(this *Expression, es *EvalState) Ex {
+			if len(this.Parts) != 2 {
+				return this
+			}
+			return NewInt(leafCount(this.Parts[1]))
+		},
+	})
 	defs = append(defs, Definition{
 		Name:              "Flat",
 		OmitDocumentation: true,

expreduce/resources/expression.m

@@ -126,3 +126,13 @@
         ESameTest[{-1, 1[{{1}, 2}], 3, 4}, Flatten[{-1, {1[{{1}, 2}]}, 3, 4}, 999]]
     ]
 };
+
+LeafCount::usage = "`LeafCount[e]` returns the count of leaves in `e`.";
+Attributes[LeafCount] = {Protected};
+Tests`LeafCount = {
+    ESimpleExamples[
+        ESameTest[3, LeafCount[a+b]],
+        ESameTest[8, LeafCount[a^2 + b^(c!)]],
+        ESameTest[1, LeafCount[a]]
+    ]
+};