provided code

.gitignore

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+.metals/
+.bsp/
+.scala-build/
+.vscode/

Makefile

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+# NOTE: PLEASE DON'T USE THIS MAKEFILE, IT IS FOR LABTS
+# it is *much* more efficient to use `scala compile .` trust me, I'm watching you.
+all:
+# the --server=false flag helps improve performance on LabTS by avoiding
+# downloading the build-server "bloop".
+# the --jvm system flag helps improve performance on LabTS by preventing
+# scala-cli from downloading a whole jdk distribution on the lab machine
+# the --force flag ensures that any existing built compiler is overwritten
+# the --power flag is needed as `package` is an experimental "power user" feature (NOTE: use this or --assembly if anything goes wrong)
+#	scala --power package . --server=false --jvm system --force -o wacc-compiler
+# you can use --assembly to make it built a self-contained jar,
+#	scala --power package . --server=false --jvm system --assembly --force -o wacc-compiler
+# you can use --native to make it build a native application (requiring Scala Native),
+#	scala --power package . --server=false --jvm system --native --force -o wacc-compiler
+# or you can use --graalvm-jvm-id graalvm-java21 --native-image to build it using graalvm
+	scala --power package . --server=false --jvm system --graalvm-jvm-id graalvm-java21 --native-image --force -o wacc-compiler
+
+clean:
+	scala clean . && rm -f wacc-compiler
+
+.PHONY: all clean

README.md

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+This is the provided git repository for the WACC compilers lab. You should work
+in this repository regularly committing and pushing your work back to GitLab.
+
+# Provided files/directories
+
+## src/main
+
+The src/main directory is where you code for your compiler should go, and just
+contains a stub hello world file with a simple calculator inside.
+
+## src/test
+The src/test directory is where you should put the code for your tests, which
+can be ran via `scala-cli test .`. The suggested framework is `scalatest`, the dependency
+for which has already been included.
+
+## project.scala
+The `project.scala` is the definition of your project's build requirements. By default,
+this skeleton has added the latest stable versions of both `scalatest` and `parsley`
+to the build: you should check **regularly** to see if your `parsley` needs updating
+during the course of WACC!
+
+## compile
+
+The compile script can be edited to change the frontend interface to your WACC
+compiler. You are free to change the language used in this script, but do not
+change its name.
+
+## Makefile
+
+Your Makefile should be edited so that running 'make' in the root directory
+builds your WACC compiler. Currently running 'make' will call
+`scala --power package . --server=false --jvm system --graalvm-jvm-id graalvm-java21 --native-image --force -o wacc-compiler`, producing a file called
+`wacc-compiler`
+in the root directory of the project. If this doesn't work for whatever reason, there are a few
+different alternatives you can try in the makefile. **Do not use the makefile as you're working, it's for labts/CI!**

compile

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+#!/bin/bash
+# Bash front-end for your compiler.
+# You are free to change the language used for this script,
+# but do *not* change its name.
+
+# feel free to adjust to suit the specific internal flags of your compiler
+./wacc-compiler "$@"
+
+exit $?

project.scala

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+//> using scala 3.6
+//> using platform jvm
+
+// dependencies
+//> using dep com.github.j-mie6::parsley::5.0.0-M10
+//> using dep com.lihaoyi::os-lib::0.11.3
+//> using test.dep org.scalatest::scalatest::3.2.19
+
+// these are all sensible defaults to catch annoying issues
+//> using options -deprecation -unchecked -feature
+//> using options -Wimplausible-patterns -Wunused:all
+//> using options -Yexplicit-nulls -Wsafe-init -Xkind-projector:underscores
+
+// these will help ensure you have access to the latest parsley releases
+// even before they land on maven proper, or snapshot versions, if necessary.
+// just in case they cause problems, however, keep them turned off unless you
+// specifically need them.
+// using repositories sonatype-s01:releases
+// using repositories sonatype-s01:snapshots
+
+// these are flags used by Scala native: if you aren't using scala-native, then they do nothing
+// lto-thin has decent linking times, and release-fast does not too much optimisation.
+// using nativeLto thin
+// using nativeGc commix
+// using nativeMode release-fast

src/main/wacc/Main.scala

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+package wacc
+
+import parsley.{Success, Failure}
+
+def main(args: Array[String]): Unit = {
+    println("hello WACC!")
+
+    args.headOption match {
+        case Some(expr) => parser.parse(expr) match {
+            case Success(x) => println(s"$expr = $x")
+            case Failure(msg) => println(msg)
+        }
+        case None => println("please enter an expression")
+    }
+}

src/main/wacc/lexer.scala

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+package wacc
+
+import parsley.Parsley
+import parsley.token.Lexer
+import parsley.token.descriptions.*
+
+object lexer {
+    private val desc = LexicalDesc.plain.copy(
+        // your configuration goes here
+    )
+    private val lexer = Lexer(desc)
+
+    val integer = lexer.lexeme.integer.decimal
+    val implicits = lexer.lexeme.symbol.implicits
+    def fully[A](p: Parsley[A]): Parsley[A] = lexer.fully(p)
+}

src/main/wacc/parser.scala

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+package wacc
+
+import parsley.{Parsley, Result}
+import parsley.expr.chain
+
+import lexer.implicits.implicitSymbol
+import lexer.{integer, fully}
+
+object parser {
+    def parse(input: String): Result[String, BigInt] = parser.parse(input)
+    private val parser = fully(expr)
+    
+    private val add = (x: BigInt, y: BigInt) => x + y
+    private val sub = (x: BigInt, y: BigInt) => x - y
+
+    private lazy val expr: Parsley[BigInt] =
+        chain.left1(integer | "(" ~> expr <~ ")")(
+            ("+" as add) | ("-" as sub)
+        )
+}

src/test/wacc/README.md

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+This is where you may wish to develop your tests. Remember that `scala-cli` picks up any files
+in a `test` sub-directory, or files ending in `.test.scala`.