simpler v0.2.1 Simpler.Contract

Very basic Design-by-Contract support.

precondition op_one > op_two
postcondition result > 0
def subtract(op_one, op_two) do
  op_one - op_two
end

You can have any number of pre- and postconditions, and they will apply to any head of the function that follows. Postconditions can use the variable result which will hold the result of the function (so, err, yeah - the Simpler.Contract.def macro is not hygienic - don’t use result in your own code. Although it usually should not conflict as this result is only assigned and used after the last line of your method body’s code).

Summary

Functions

def(name_and_args, body)

Override of def that will run current contract definitions

postcondition(stuff)

Define a postcondition. A special variable result holds the result of the function. If the postcondition doesn’t hold, raise an error

precondition(stuff)

Define a precondition. Argument names should be availablable in any function head’s arguments. If the precondition doesn’t hold, raise an error

Functions

def(name_and_args, body) (macro)

Override of def that will run current contract definitions.

postcondition(stuff) (macro)

Define a postcondition. A special variable result holds the result of the function. If the postcondition doesn’t hold, raise an error.

precondition(stuff) (macro)

Define a precondition. Argument names should be availablable in any function head’s arguments. If the precondition doesn’t hold, raise an error.