Patent claims define the legal scope: if "using Swift" isn't in the claims then using another language, provided it fits the language of the claims, is also covered by the patent.
ok, does it mean that if you implement only parts of the patent (say only a single feature) there's no infringement because then it doesn't "fit the language of the claims"?
If you look at the main claims (any that don't add to a previous claim, ie don't include "the invention of claim X wherein ...") then you need to be doing something that matches all clauses in the claim to infringe.
When drafting the claims writer (patent attorney or agent usually) will add clauses to work around prior art. You can't just add unrelated features though, the features need to have synergy to represent a single invention.
[I've read a lot on USA patents but only worked directly with UK and EU patents.
