Fix length for BasicSymbolic

Author: bowenszhu

src/utils.jl

@@ -183,7 +183,12 @@ Base.length(l::LL) = length(l.v)-l.i+1
 @inline car(l::LL) = l.v[l.i]
 @inline cdr(l::LL) = isempty(l) ? empty(l) : LL(l.v, l.i+1)
 
-Base.length(t::BasicSymbolic) = length(arguments(t)) + 1 # PIRACY
+function Base.length(t::BasicSymbolic)
+    @match t.impl begin
+        Term(_...) => length(arguments(t)) + 1 # PIRACY
+        _ => 1
+    end
+end
 Base.isempty(t::BasicSymbolic) = false
 @inline car(t::BasicSymbolic) = operation(t)
 @inline cdr(t::BasicSymbolic) = arguments(t)