lambda-express | AWS Lambda Function to Integrate with Express | Cloud Functions library

mapcar is by itself a primitive applicative operator (pag. 220 of Common Lisp: A gentle introduction to Symbolic Computation). So, if you want to rewrite it in an applicative way, you should use some other primitive applicative operator, for instance map or map-into. For instance, with map-into:

std::any_cast needs to cast to constructible types. A standard C++ function is neither a type nor constructible (it's just a group of statements given a name [edit: this isn't technically true, but what's going on under the hood is fairly complicated]), but std::function is. One way to get around this is to assign a standard C++ function to an std::function. Here's an example using a std::map like you were using:

Per Jonathan Caves reply on the feature request, the supported syntax going forward is

Is the following not an option?

In this code, the lambda function "sees" the argument x and the variable n, which is in the lambda's closure:

It's complaining because lambdas can't be used as template arguments (before C++20 anyway). Otherwise, lambdas are already callable objects that will not throw unless the function body throws, no wrapper class needed. You just have to do this awkwardness:

ApplicationTypeID is nullable, so check it for a value before comparing:

SFINAE can be used in order to direct the compiler to choose a particular function overload, or a particular partial specialization of a class template. In the first case, substitution failures remove declarations from the overload set and in the second case, substitution failures remove the partial specialization declarations from consideration (causing either the primary template to be used, or a different partial specialization for which substitution succeeds).

But what you are trying to do here is backward: you have a situation where the primary template is potentially subject to substitution error, and you provide a partial specialization as an alternative. This can never work. Partial specialization matching begins after the template argument list to the primary template is fully known, therefore if a substitution error occurs in the primary template's template argument list, no specializations can be considered.

For example if we have

For that code to compile, you must have Option Strict Off. You should fix that immediately. Your field is being implicitly typed as Object and you can't call an Object reference.

With Option Strict On, you would be forced to specify a type for that field. The obvious type is Action: