add system.version()

[kroggen]

This function returns the hardfork version of the underlying blockchain

[kroggen]

TODO:

• [x] add functional tests
• [ ] add gas test (gas-per-function)

[kroggen]

It is intended to be used like this:

  if system.version() >= 4 then
    ...
  end

[kroggen]

Another option to check if a function is available:

if type(bignum.ispositive) == "function" then
  ...
end

But it only works for functions on existing modules. This will fail if the name_service module is not available:

if type(name_service.resolve) == "function" then
  ...
end

error: attempt to index global 'name_service' (a nil value)

This method checks for the module and for the function:

if name_service ~= nil and type(name_service.resolve) == "function" then
  ...
end