hw2 students question

Author: TheMrGhostman

docs/src/lectures/lecture_03/hw2_optimal_solutions.jl

@@ -0,0 +1,19 @@
+##  agent_count
+### recommended option
+agent_count(a::Animal) = 1.0
+agent_count(p::Plant) = p.size / p.max_size
+
+## agent_count(agents::Vector{<:Agent})
+### recommended option
+agent_count(as::Vector{<:Agent}) = sum(agent_count,as)
+
+## agent_count(w::World)
+### recommended option (little fancy)
+function agent_count(w::World)
+    function op(d::Dict,a::A) where A<:Agent
+        n = nameof(A)
+        d[n] = haskey(d,n) ? d[n]+agent_count(a) : agent_count(a)
+        return d
+    end
+    reduce(op, w.agents |> values, init=Dict{Symbol,Float64}())
+end