i am not familiar with fstar. But I will try to provide some context badly so someone who does know it can correct me. Javascript is dynamically typed, and so

i am not familiar with fstar. But I will try to provide some context badly so someone who does know it can correct me. Javascript is dynamically typed, and so has no type checking until runtime, you don't know whether a passed in parameter is a string or not until you try to use it. C# is statically typed, so the compiler knows whether something is a string when passed in at compile time, not making you wait until runtime. Ocaml/F# have a stronger type system than c#, so you get the compiler looking for you not only that something is a string, but that it is a named type like fifteenString, which is a string with a length of always 15 characters. F* takes this even further, where the compiler checks for you that you've passed in a fifteenString and that it matches criteria in its value like "starts with hello" or "does not contain bye". C# saves you from needing to check if a param is even a astring at runtime. F# additionally saves you from needing to check if it is null and 15 characters in length at runtime. F* additionally saves you needing to check its value starts with hello at runtime. Again this is a single language feature probably poorly explained!