Added repl and some documentation. Improved error messages. Removed dead code.

* Removed same_variant in parse::parsetree
* Added SExp::multistep (for use of the repl)

Improved error messages:
* Added parenthesis around types
* Changed how errors propagate inferring generics:
  added the error variant ArgumentsDontMatchGeneric,
  implemented the displaying of it, added tests for
  it.
* Had to change some tests to match for the new changes

1 files changed, 63 insertions, 0 deletions

diff --git a/README.md b/README.md
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+
+
+myslip README
+=============
+
+Below is a short introduction to this programming language
+and instructions on setting it up.
+`TUTORIAL.md` may help getting familiar with the language.
+
+
+Language introduction
+---------------------
+STILL TODO (or to modify)
+how functional is it?
+myslip is a lisp-inspired language, but a bit different
+(mostly, because I have never really written lisp except
+ for in emacs, so I have no clue of what lisp usually is
+ like).
+Valid myslip s-expressions may be atoms of different types
+or lists of them, though not all syntactically valid
+myslip expressions are ones that can be evaluated.
+
+S-expression := Atom | List
+Atom := TODO
+List := (S-expression ... S-expression)
+
+The myslip interpreter performs type checking on
+s-expressions and evaluates them according to polish
+notation, ie. the first S-expression of a list is taken to
+be the operator that is passed the rest of the expressions
+as arguments.
+
+
+Running the project
+-------------------
+
+myslip can be built using cargo 1.88.0. Instructions to
+install cargo can be found online:
+https://doc.rust-lang.org/cargo/getting-started/installation.html
+
+If you are having trouble due to having a different version
+and you used rustup for your cargo installation, you can
+follow these instructions on how to change the rust version
+https://rust-lang.github.io/rustup/overrides.html
+
+TODO: system requirements? try it out on debian
+```console
+TODO
+$ sudo apt install curl git
+$ curl ??? | sh ???
+$ git clone ???
+$ cd myslip
+```
+and then the interpreter can be accessed either via
+`cargo run`, or then you can add it to your path:
+```console
+TODO
+$ cargo build
+$ ln ??? ???
+$ myslip
+```
+
+