Add labs 4-6 handouts

labs/labs06_material/presentation.md

+## Compiler Extension Presentation Instructions
+
+Background presentations will take place in week 14. We strongly
+recommend that you pre-record your presentation. **[You should upload
+your talk on SwitchTube](https://tube.switch.ch/channels/c1d660a4)**
+(the precise channel will be linked here soon). However, if you prefer,
+you can also live stream your presentation, but in that case you are
+responsible if the presentation does not reach your audience due to
+network quality issues.
+
+**The presentation should be 10 minutes long.**
+
+**Q&A session of 5-10 minutes** will follow right after the
+presentation. Please make sure at least one of you is available for the
+entire 20 minute slot.
+
+**We would like each member of the group to be part of the
+presentation.**
+
+Shortly after, you will receive feedback from us regarding the content
+of your presentation, as well as some general feedback on the form.
+
+### Presentation content
+
+Your presentation should summarize your project. In particular, we\'d
+expect to see
+
+-   a basic overview of the features you added to the compiler/language
+-   some (short) programs highlighting the use of these features, with a
+    description of how your extended compiler behaves on them
+-   possibly some theoretical background you had to learn about to
+    implement the extension
+-   an overview of the changes you made to each compiler phase and/or
+    which phases you added
+
+### Presentation style
+
+Here are some useful resources on how to prepare and give talks:
+
+-   [How To Speak by Patrick
+    Winston](https://www.youtube.com/watch?v=Unzc731iCUY)
+-   [How to give a great research talk by Simon Peyton
+    Jones](https://www.microsoft.com/en-us/research/academic-program/give-great-research-talk/)
+
+Please do not use Viktor\'s videos as a model for the presentation, but
+instead incorporate as many points of the talk of [Patrick
+Winston](https://en.wikipedia.org/wiki/Patrick_Winston) as you believe
+apply to your presentation. It is an amazing and entertaining talk,
+despite (or because) it is meta-circular: he does as he says. Note:
+breaking physical objects or referring to supernatural beings in your
+video is not required. Use your own judgement and strike a balance in
+being comfortable with what and how you are saying things and trying out
+these pieces of advice.
+
+### Instructions for video (recording or streaming)
+
+We suggest that the speaker\'s video shows up when the speaker starts to
+speak, so that the audience can relate and identify the speaker.
+Afterwards, the video can be turned off and should come back on for
+questions and answers. Optionally, a small video can stay on throughout
+the presentation. The main content of the presentation should be a
+window showing the material being presented, for example as a PDF to
+which you can point to and/or annotate it. If the hardware allows you,
+you can also use a tablet to simulate a blackboard presentation where
+you write down everything you present, or use a combination or simple
+slides and a strategy of what you will write on them.
+
+**Video upload:** [please upload your video to this
+channel](https://tube.switch.ch/channels/c1d660a4) (login with EPFL
+credentials)
+
+### Viktor\'s recording setup
+
+For your information and not as a requirement, Viktor\'s lectures are
+prepared using this hardware and software setup on Ubuntu 20 OS:
+
+-   slides prepared using the \`beamer\` latex package
+-   slides annotated using \`xournal\` PDF annotator in full screen mode
+    on display size 1920x1080
+-   recording using Zoom, with the following options:
+    -   screen sharing PDF annotator (\`xournal\`), **without** option
+        to optimize for full-screen viewing
+    -   local recording, with option **Optimize for 3rd party video
+        editor**
+-   wacom cintiq pro display as external monitor for annotating PDF\'s
+    using pen
+-   video segments are cut and assembled using ffmpeg, which works very
+    fast:
+    -   cut like this:
+
+```{=html}
+<!-- -->
+```
+    fmpeg -i zoom_0.mp4 -ss 00:00:00 -to 00:02:03.00 -c copy mysegment01.mp4
+
+      * concatenate like this:
+
+    ffmpeg -f concat -i segmentlist.txt -c copy mycombinedvideo.mp4
+
+where segmentlist.txt is a file containing one line per each file to
+include:
+
+    file 'mysegment01.mp4'
+    file 'mysegment02.mp4'
+    file 'mysegment03.mp4'
+
+Alternatively, you can also use \`obs\` open source software. For
+recording, under advanced options, you may wish to choose a 1 second key
+frame interval to make cutting the video with ffmpeg work well.

labs/labs_04.md

+# Lab 04: Type Checker
+
+Parsing concludes the syntactical analysis of Amy programs. Having
+successfully constructed an abstract syntax tree for an input program,
+compilers typically run one or multiple phases containing checks of a
+more semantical nature. Virtually all high-level programming languages
+enjoy some form of name analysis, whose purpose is to disambiguate
+symbol references throughout the program. Some languages go further and
+perform a series of additional checks whose goal is to rule out runtime
+errors statically (i.e., during compilation, or in other words, without
+executing the program). While the exact rules for those checks vary from
+language to language, this part of compilation is typically summarized
+as \"type checking\". Amy, being a statically-typed language, requires
+both name and type analysis.
+
+## Prelude: From Nominal to Symbolic Trees
+
+Recall that during parsing we created (abstract syntax) trees of the
+*nominal* sort: Names of variables, functions and data types were simply
+stored as strings. However, two names used in the program could be the
+same, but not refer to one and the same \"thing\" at runtime. During
+name analysis we translate from nominal trees to symbolic ones, to make
+it clear whether two names refer to one and the same underlying entity.
+That is, we explicitly replace strings by fresh identifiers which will
+prevent us from mixing up definitions of the same name, or referring to
+things that have not been defined. Amy\'s name analyzer is provided to
+you as part of this lab\'s skeleton, but you should read the [dedicated
+name analyzer page](name analyzer) to understand how it works.
+
+## Introduction to Type Checking
+
+The purpose of this lab is to implement a type checker for Amy. Our type
+checking rules will prevent certain errors based on the kind or shape of
+values that the program is manipulating. For instance, we should prevent
+an integer from being added to a boolean value.
+
+Type checking is the last stage of the compiler frontend. Every program
+that reaches the end of this stage without an error is correct (as far
+as the compiler is concerned), and every program that does not is wrong.
+After type checking we are finally ready to interpret the program or
+compile it to binary code!
+
+Typing rules for Amy are presented in detail in the
+[Amy specification](amy_specification.md). Make sure to check correct
+typing for all expressions and patterns.
+
+## Implementation
+
+The current assignment focuses on the file `TypeChecker.scala`. As
+usual, the skeleton and helper methods are given to you, and you will
+have to complete the missing parts. In particular, you will write a
+compiler phase that checks whether the expressions in a given program
+are well-typed and report errors otherwise.
+
+To this end you will implement a simplified form of the Hindley-Milner
+(HM) type-inference algorithm that you\'ll hear about during the
+lectures. Note that while not advertised as a feature to users of Amy,
+behind the scenes we will perform type inference. It is usually
+straightforward to adapt an algorithm for type inference to type
+checking, since one can add the user-provided type annotations to the
+set of constraints. This is what you will do with HM in this lab.
+
+Compared to the presentation of HM type inference in class your type
+checker can be simplified in another way: Since Amy does not feature
+higher-order functions or polymorphic data types, types in Amy are
+always *simple* in the sense that they are not composed of arbitrary
+other types. That is, a type is either a base type (one of `Int`, `Bool`
+and `String`) or it is an ADT, which has a proper name (e.g. `List` or
+`Option` from the standard library). In the latter case, all the types
+in the constructor of the ADT are immediately known. For instance, the
+standard library\'s `List` is really a list of integers, so we know that
+the `Cons` constructor takes an `Int` and another `List`.
+
+As a result, your algorithm will never have to deal with complex
+constraints over type constructors (such as the function arrow
+`A => B`). Instead, your constraints will always be of the form
+`T1 = T2` where `T1` and `T2` are either *simple* types or type
+variables. This is most important during unification, which otherwise
+would have to deal with complex types separately.
+
+Your task now is to a) complete the `genConstraints` method which will
+traverse a given expression and collect all the necessary typing
+constraints, and b) implement the *unification* algorithm as
+`solveConstraints`.
+
+Familiarize yourself with the `Constraint` and `TypeVariable` data
+structures in `TypeChecker.scala` and then start by implementing
+`genConstraints`. The structure of this method will in many cases be
+analogous to the AST traversal you wrote for the name analyzer. Note
+that `genConstraints` also takes an *expected type*. For instance, in
+case of addition the expected type of both operands should be `Int`. For
+other constructs, such as pattern `match`es it is not inherently clear
+what should be the type of each `case` body. In this case you can create
+and pass a fresh type variable.
+
+Once you have a working implementation of both `genConstraints` and
+`solveConstraints` you can copy over your previous work on the
+interpreter and run the programs produced by your frontend! Don\'t
+forget that to debug your compiler\'s behavior you can also use the
+reference compiler with the `--interpret` flag and then compare the
+output.
+
+## Skeleton
+
+As usual, you can find the skeleton for this lab in a new branch of your
+group\'s repository. After merging it with your existing work, the
+structure of your project `src` directory should be as follows:
+
+    src/amyc
+     ├── Main.scala                (updated)
+     │
+     ├── analyzer                  (new)
+     │    ├── SymbolTable.scala
+     │    ├── NameAnalyzer.scala
+     │    └── TypeChecker.scala
+     │
+     ├── ast
+     │    ├── Identifier.scala
+     │    ├── Printer.scala
+     │    └── TreeModule.scala
+     │
+     ├── interpreter
+     │    └── Interpreter.scala
+     │
+     ├── lib
+     │    ├── scallion_3.0.6.jar
+     │    └── silex_3.0.6.jar
+     │
+     ├── parsing
+     │    ├── Parser.scala
+     │    ├── Lexer.scala
+     │    └── Tokens.scala
+     │
+     └── utils
+          ├── AmycFatalError.scala
+          ├── Context.scala
+          ├── Document.scala
+          ├── Pipeline.scala
+          ├── Position.scala
+          ├── Reporter.scala
+          └── UniqueCounter.scala
+
+## Deliverables
+
+You are given **3 weeks** for this assignment.
+
+Deadline: **TBD**.
+
+Submission: one team member submits a zip file submission-groupNumber.zip to the [moodle submission page]().

labs/labs_05.md

+# Lab 05: Code Generation
+
+## Introduction
+
+Welcome to the last common assignment for the Amy compiler. At this
+point, we are finally done with the frontend: we have translated source
+programs to ASTs and have checked that all correctness conditions hold
+for our program. We are ready to generate code for our program. In our
+case the target language will be *WebAssembly*.
+
+WebAssembly is \"a new portable, size- and load-time-efficient format
+suitable for compilation to the web\" (<http://webassembly.org>).
+WebAssembly is designed to be called from JavaScript in browsers and
+lends itself to highly-performant execution.
+
+For simplicity, we will not use a browser, but execute the resulting
+WebAssembly bytecode directly using `nodejs` which is essentially a
+standalone distribution of the Chrome browser\'s JavaScript engine. When
+you run your complete compiler (or the reference compiler) with no
+options on program `p`, it will generate four different files under the
+`wasmout` directory:
+
+-   `p.wat` is the wasm output of the compiler in text format. You can
+    use this representation to debug your generated code.
+-   `p.wasm` is the binary output of the compiler. This is what `nodejs`
+    will use. To translate to the binary format, we use the `wat2wasm`
+    tool provided by the WebAssembly developers. For your convenience we
+    have included it in the `bin` directory of the skeleton. Note that
+    this tool performs a purely mechanical translation and thus its
+    output (for instance, `p.wasm`) corresponds to a binary
+    representation of `p.wat`.
+-   `p.js` is a JavaScript wrapper which we will run with nodejs and
+    serve as an entrypoint into your generated binary.
+
+To run the program, simply type `nodejs wasmout/p.js`
+
+### Installing nodejs
+
+-   You can find directions for your favorite operating system
+    [here](https://nodejs.org/en/). You should have nodejs 12 or later
+    (run `nodejs --version` to make sure).
+-   Once you have installed nodejs, run `npm install deasync` from the
+    directory you plan to run `amyc` in, i.e. the toplevel directory of
+    the compiler.
+-   Make sure the `wat2wasm` executable is visible, i.e. it is in the
+    system path or you are at the toplevel of the `amyc` directory.
+
+## WebAssembly and Amy
+
+Look at [this
+presentation](http://lara.epfl.ch/~gschmid/clp20/codegen.pdf) for the
+main concepts of how to translate Amy programs to WebAssembly.
+
+You can find the annotated compiler output to the concat example
+[here](http://lara.epfl.ch/~gschmid/clp20/concat.wat).
+
+## The assignment code
+
+### Overview
+
+The code for the assignment is divided into two directories: `wasm` for
+the modeling of the WebAssembly framework, and `codegen` for
+Amy-specific code generation. There is a lot of code here, but your task
+is only to implement code generation for Amy expressions within
+`codegen/CodeGen.scala`.
+
+-   `wasm/Instructions.scala` provides types that describe a subset of
+    WebAssembly instructions. It also provides a type `Code` to describe
+    sequences of instructions. You can chain multiple instructions or
+    `Code` objects together to generate a longer `Code` with the `<:>`
+    operator.
+-   `wasm/Function.scala` describes a wasm function.
+    -   `LocalsHandler` is an object which will create fresh indexes for
+        local variables as needed.
+    -   A `Function` contains a field called `isMain` which is used to
+        denote a main function without a return value, which will be
+        handled differently when printing, and will be exported to
+        JavaScript.
+    -   The only way to create a `Function` is using `Function.apply`.
+        Its last argument is a function from a `LocalsHandler` to
+        `Code`. The reason for this unusual choice is to make sure the
+        Function object is instantiated with the number of local
+        variables that will be requested from the LocalsHandler. To see
+        how it is used, you can look in `codegen/Utils.scala` (but you
+        won\'t have to use it directly).
+-   `wasm/Module.scala` and `wasm/ModulePrinter.scala` describe a wasm
+    module, which you can think of as a set of functions and the
+    corresponding module headers.
+-   `codegen/Utils.scala` contains a few utility functions (which you
+    should use!) and implementations of the built-in functions of Amy.
+    Use the built-ins as examples.
+-   `codegen/CodeGen.scala` is the focus of the assignment. It contains
+    code to translate Amy modules, functions and expressions to wasm
+    code. It is a pipeline and returns a wasm Module.
+-   `codegen/CodePrinter.scala` is a Pipeline which will print output
+    files from the wasm module.
+
+### The cgExpr function
+
+The focus of this assignment is the `cgExpr` function, which takes an
+expression and generates a `Code` object. It also takes two additional
+arguments: (1) a `LocalsHandler` which you can use to get a new slot for
+a local when you encounter a local variable or you need a temporary
+variable for your computation. (2) a map `locals` from `Identifiers` to
+locals slots, i.e. indices, in the wasm world. For example, if `locals`
+contains a pair `i -> 4`, we know that `get_local 4` in wasm will push
+the value of i to the stack. Notice how `locals` is instantiated with
+the function parameters in `cgFunction`.
+
+## Skeleton
+
+As usual, you can find the skeleton for this lab in a new branch of your
+group\'s repository. After merging it with your existing work, the
+structure of your project `src` directory should be as follows:
+
+    src/amyc
+     ├── Main.scala                (updated)
+     │
+     ├── analyzer   
+     │    ├── SymbolTable.scala
+     │    ├── NameAnalyzer.scala
+     │    └── TypeChecker.scala
+     │
+     ├── ast
+     │    ├── Identifier.scala
+     │    ├── Printer.scala
+     │    └── TreeModule.scala
+     │
+     ├── bin
+     │    └── ...
+     │
+     ├── codegen                  (new)      
+     │    ├── CodeGen.scala
+     │    ├── CodePrinter.scala
+     │    └── Utils.scala
+     │
+     ├── interpreter
+     │    └── Interpreter.scala
+     │
+     ├── lib
+     │    ├── scallion_3.0.6.jar
+     │    └── silex_3.0.6.jar
+     │
+     ├── parsing
+     │    ├── Parser.scala
+     │    ├── Lexer.scala
+     │    └── Tokens.scala
+     │
+     ├── utils
+     │    ├── AmycFatalError.scala
+     │    ├── Context.scala
+     │    ├── Document.scala
+     │    ├── Pipeline.scala
+     │    ├── Position.scala
+     │    ├── Reporter.scala
+     │    └── UniqueCounter.scala
+     │
+     └── wasm                     (new)
+          ├── Function.scala
+          ├── Instructions.scala 
+          ├── ModulePrinter.scala
+          └── Module.scala
+
+## Deliverables
+
+You are given **4 weeks** for this assignment.
+
+Deadline: **TBD**.
+
+Submission: one team member submits a zip file submission-groupNumber.zip to the [moodle submission page]().

labs/labs_06.md

+# Labs 06: Compiler extension project
+
+You have now written a compiler for Amy, a simple functional language.
+The final lab project is to design and implement a new functionality of
+your own choice on top of the compiler you built so far. In preparation
+for this, you should aim to learn about the problem domain by searching
+the appropriate literature. The project includes:
+
+-   designing and implementing the new functionality
+-   documenting the results in a written report document
+
+This project has several deadlines, detailed below. Please note that the
+first of them (choosing the topic) is already coming up on Sunday!
+
+## Selecting a Project Topic
+
+**Deadline: TBD**
+
+In the following document, we list several project ideas, but you should
+also feel free to submit your own by email. All groups will rank the
+projects in order of preference, and we will then do our best to assign
+the preferred projects to as many groups as possible. Because not all
+projects are equally difficult, we annotated each of them with the
+expected workload. The suggested projects cover a wide range of
+complexity, and we will evaluate your submissions with that complexity
+in mind. For instance, for a project marked with `(1)` (relatively low
+complexity) we will be expecting a polished, well-tested and
+well-documented extension, whereas projects on the other end (`(3)`) may
+be more prototypical. For all submissions, however, we require that you
+deliver code that compiles and a set of example input files that
+demonstrate the new functionality.
+
+[Project ideas](labs06_material/extensions.pdf)
+
+To announce your preferences, [please fill out this form by Sunday at
+the latest](). You\'ll have to
+provide **the names of the top exactly 5** projects you would like to
+work on, in order of descending preference. We will do our best to
+assign you the project you are most interested in.
+
+## Project Orientation
+
+**Deadline: TBD**
+
+We will try to inform you about the project assignment as soon as
+possible. To give you a chance to validate your understanding of the
+project and what\'s expected of you, we will offer dedicated slots
+during the project sessions next week. Before you join, you should think
+about the following questions
+
+-   What are the features you will add to the compiler/language?
+-   What would be some (short) programs highlighting the use of these
+    features?
+-   What changes might be required in each compiler phase and/or what
+    new phases would you add? (Very roughly)
+
+**TODO: define slots**
+
+## Project Presentation
+
+You will present your idea during the lab sessions on the last regular
+week of the semester (Dec 16th/22nd/23rd). We\'ll announce the concrete
+schedule of presentations at a later point. [Instructions on what and
+how to present your project can be found here.](labs06_material/presentation.md)
+
+## Project Implementation and Report
+
+**Deadline: Jan 7th 2021 23h00**
+
+Your implementation and a report are due on this date, and both will be
+delivered using Git. You will develop your project on top of your
+implementation of Amy. Please push all development on a new branch
+`lab06`, ideally building on top of the codegen lab (branch `lab05`). 
+**TODO: define submission method**
+
+Your repository should contain:
+
+-   Your implementation, which must, to be graded at all, compile and be
+    able to run non-trivial examples.
+-   A subdirectory `extension-examples/` which includes some examples
+    that demonstrate your compiler extension in action.
+-   A subdirectory `report/` which includes a PDF summarizing your
+    extension.
+
+**If you did not manage to complete your planned features, or they are
+partially implemented, make this clear in your report!**
+
+You are encouraged to use the following (LaTeX) template for your
+report:
+
+-   [LaTeX sources](labs06_material/report-template.tar.gz)
+
+A PDF version of the template with the required section is available
+here:
+
+-   [PDF Example](labs06_material/report-template.pdf)
+
+Although you are not required to use the above template, your report
+must contain at least the sections described in it with the appropriate
+information. Note that writing this report will take some time, and you
+should not do it in the last minute. The final report is an important
+part of the compiler project. If you have questions about the template
+or the contents of the report, make sure you ask them early.
+
+A common question is \"how long should the report be?\". There\'s no
+definitive answer to that. Considering that the report will contain code
+examples and a technical description of your implementation, it would be
+surprising if it were shorter than 3 pages. Please try to stay within 6
+pages. A concise, but well-written report is preferable to a long, but
+poorly-written one.