#58 - added check for interface function existence

src/helper_functions.jl

@@ -1,7 +1,8 @@
 import Base.<=
 
 export sign_cadlag,
-       jump2pi
+       jump2pi,
+       check_method_implementation
 
 """
     sign_cadlag(x::N)::N where {N<:Real}
@@ -86,3 +87,68 @@ direction (1, 0).
 function <=(u::AbstractVector{Float64}, v::AbstractVector{Float64})::Bool
     return jump2pi(atan2(u[2], u[1])) <= jump2pi(atan2(v[2], v[1]))
 end
+
+"""
+    check_method_implementation(interface::Type,
+                                func_name,
+                                args_funcs::AbstractVector{Function},
+                                [print_results]::Bool=false
+                               )::Bool
+
+Check that a given (interface) function is implemented by all subtypes.
+
+### Input
+
+- `interface`     -- parent interface type
+- `func_name`     -- function name
+- `args_funcs`    -- list of functions that each map a type to an argument
+                     signature tuple
+- `print_results` -- (optional, default: `false`) flag for printing intermediate
+                     results
+
+### Output
+
+`true` iff all subtypes implement the given function.
+
+### Notes
+
+It is sufficient that a subinterface implements the function, i.e., it is not
+required that every *concrete* type implements the function.
+
+This function can also print all intermediate results to STDOUT.
+
+### Examples
+
+```julia
+check_method_implementation(LazySet, σ,
+        Function[S -> (AbstractVector{Float64}, S)])
+true
+```
+"""
+function check_method_implementation(interface::Type,
+                                     func_name,
+                                     args_funcs::AbstractVector{Function};
+                                     print_results::Bool=false
+                                    )::Bool
+    for subtype in subtypes(interface)
+        found = false
+        for args_func in args_funcs
+            if method_exists(func_name, args_func(subtype))
+                if print_results
+                    println("found implementation of $func_name for $subtype")
+                end
+                found = true
+                break
+            end
+        end
+        if !found && !check_method_implementation(subtype, func_name,
+                                                  args_funcs,
+                                                  print_results=print_results)
+            if print_results
+                println("no implementation of $func_name for $subtype")
+            end
+            return false
+        end
+    end
+    return true
+end