What makes you say the language is not consistent? Default parameters are a feature of named functions. Currying is a different feature of functions. A curried

What makes you say the language is not consistent? Default parameters are a feature of named functions. Currying is a different feature of functions. A curried function is equivalent to a non-curried function that returns a function. Since the returned function is not a named function, it cannot have default parameters. Therefore, default parameters are not allowed in curried functions. Beyond that, the author's proposed API is most definitely not the best API design to use here, even if the default parameters did work in curried functions. A builder pattern would make a lot more sense. Or just do as Cocoa already does and provide a request object that can be customized before initiating the HTTP call.