language: implement let definitions

ast/src/main/ast/pork.yml

@@ -137,6 +137,15 @@ types:
       type: Block?
     - name: native
       type: Native?
+  LetDefinition:
+    parent: Definition
+    values:
+    - name: modifiers
+      type: DefinitionModifiers
+    - name: symbol
+      type: Symbol
+    - name: value
+      type: Expression
   If:
     parent: Expression
     values:

ast/src/main/graph/types.dot

@@ -16,6 +16,7 @@ digraph A {
   type_FunctionCall [shape=box,label="FunctionCall"]
   type_ArgumentSpec [shape=box,label="ArgumentSpec"]
   type_FunctionDefinition [shape=box,label="FunctionDefinition"]
+  type_LetDefinition [shape=box,label="LetDefinition"]
   type_If [shape=box,label="If"]
   type_ImportDeclaration [shape=box,label="ImportDeclaration"]
   type_IntegerLiteral [shape=box,label="IntegerLiteral"]
@@ -58,6 +59,7 @@ digraph A {
   type_Expression -> type_Break
   type_Expression -> type_Continue
   type_Definition -> type_FunctionDefinition
+  type_Definition -> type_LetDefinition
   type_Declaration -> type_ImportDeclaration
   type_Definition -> type_Symbol [style=dotted]
   type_Definition -> type_DefinitionModifiers [style=dotted]
@@ -80,6 +82,9 @@ digraph A {
   type_FunctionDefinition -> type_ArgumentSpec [style=dotted]
   type_FunctionDefinition -> type_Block [style=dotted]
   type_FunctionDefinition -> type_Native [style=dotted]
+  type_LetDefinition -> type_DefinitionModifiers [style=dotted]
+  type_LetDefinition -> type_Symbol [style=dotted]
+  type_LetDefinition -> type_Expression [style=dotted]
   type_If -> type_Expression [style=dotted]
   type_If -> type_Block [style=dotted]
   type_ImportDeclaration -> type_Symbol [style=dotted]

ast/src/main/kotlin/gay/pizza/pork/ast/LetDefinition.kt

@@ -0,0 +1,30 @@
+// GENERATED CODE FROM PORK AST CODEGEN
+package gay.pizza.pork.ast
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+@SerialName("letDefinition")
+class LetDefinition(override val modifiers: DefinitionModifiers, override val symbol: Symbol, val value: Expression) : Definition() {
+  override val type: NodeType = NodeType.LetDefinition
+
+  override fun <T> visitChildren(visitor: NodeVisitor<T>): List<T> =
+    visitor.visitNodes(symbol, value)
+
+  override fun <T> visit(visitor: NodeVisitor<T>): T =
+    visitor.visitLetDefinition(this)
+
+  override fun equals(other: Any?): Boolean {
+    if (other !is LetDefinition) return false
+    return other.modifiers == modifiers && other.symbol == symbol && other.value == value
+  }
+
+  override fun hashCode(): Int {
+    var result = modifiers.hashCode()
+    result = 31 * result + symbol.hashCode()
+    result = 31 * result + value.hashCode()
+    result = 31 * result + type.hashCode()
+    return result
+  }
+}

ast/src/main/kotlin/gay/pizza/pork/ast/NodeCoalescer.kt

@@ -41,6 +41,9 @@ class NodeCoalescer(val handler: (Node) -> Unit) : NodeVisitor<Unit> {
   override fun visitLetAssignment(node: LetAssignment): Unit =
     handle(node)
 
+  override fun visitLetDefinition(node: LetDefinition): Unit =
+    handle(node)
+
   override fun visitListLiteral(node: ListLiteral): Unit =
     handle(node)
 

ast/src/main/kotlin/gay/pizza/pork/ast/NodeType.kt

@@ -19,6 +19,7 @@ enum class NodeType(val parent: NodeType? = null) {
   InfixOperation(Expression),
   IntegerLiteral(Expression),
   LetAssignment(Expression),
+  LetDefinition(Definition),
   ListLiteral(Expression),
   Native(Node),
   Parentheses(Expression),

ast/src/main/kotlin/gay/pizza/pork/ast/NodeVisitor.kt

@@ -28,6 +28,8 @@ interface NodeVisitor<T> {
 
   fun visitLetAssignment(node: LetAssignment): T
 
+  fun visitLetDefinition(node: LetDefinition): T
+
   fun visitListLiteral(node: ListLiteral): T
 
   fun visitNative(node: Native): T

ast/src/main/kotlin/gay/pizza/pork/ast/NodeVisitorExtensions.kt

@@ -13,6 +13,7 @@ fun <T> NodeVisitor<T>.visit(node: Node): T =
     is BooleanLiteral -> visitBooleanLiteral(node)
     is FunctionCall -> visitFunctionCall(node)
     is FunctionDefinition -> visitFunctionDefinition(node)
+    is LetDefinition -> visitLetDefinition(node)
     is If -> visitIf(node)
     is ImportDeclaration -> visitImportDeclaration(node)
     is IntegerLiteral -> visitIntegerLiteral(node)

evaluator/src/main/kotlin/gay/pizza/pork/evaluator/CompilationUnitContext.kt

@@ -39,6 +39,10 @@ class CompilationUnitContext(
 
   private fun definitionValue(definition: Definition): Any = when (definition) {
     is FunctionDefinition -> FunctionContext(this, definition)
+    is LetDefinition -> {
+      EvaluationVisitor(internalScope.fork("let ${definition.symbol.id}"))
+        .visit(definition.value)
+    }
   }
 
   private fun processAllImports() {

evaluator/src/main/kotlin/gay/pizza/pork/evaluator/EvaluationVisitor.kt

@@ -30,6 +30,10 @@ class EvaluationVisitor(root: Scope) : NodeVisitor<Any> {
     return value
   }
 
+  override fun visitLetDefinition(node: LetDefinition): Any {
+    topLevelUsedError("LetDefinition", "CompilationUnitContext")
+  }
+
   override fun visitSymbolReference(node: SymbolReference): Any =
     currentScope.value(node.symbol.id)
 

examples/count.pork

@@ -1,7 +1,9 @@
+let count = 5
+
 export func main() {
   var x = 1
-  while x <= 5 {
+  while x <= count {
     println(x)
-    x = x + 1
+    x++
   }
 }

parser/src/main/kotlin/gay/pizza/pork/parser/Parser.kt

@@ -226,7 +226,7 @@ class Parser(source: PeekableSource<Token>, val attribution: NodeAttribution) {
     ImportDeclaration(form, components)
   }
 
-  private fun readFunctionDeclaration(): FunctionDefinition = within {
+  private fun readDefinitionModifiers(): DefinitionModifiers {
     val modifiers = DefinitionModifiers(export = false)
     while (true) {
       val token = peek()
@@ -238,12 +238,16 @@ class Parser(source: PeekableSource<Token>, val attribution: NodeAttribution) {
         else -> break
       }
     }
+    return modifiers
+  }
+
+  private fun readFunctionDeclaration(modifiers: DefinitionModifiers): FunctionDefinition = within {
     expect(TokenType.Func)
     val name = readSymbolRaw()
     expect(TokenType.LeftParentheses)
     val arguments = collect(TokenType.RightParentheses, TokenType.Comma) {
       val symbol = readSymbolRaw()
-      var multiple: Boolean = false
+      var multiple = false
       if (next(TokenType.DotDotDot)) {
         multiple = true
       }
@@ -261,11 +265,21 @@ class Parser(source: PeekableSource<Token>, val attribution: NodeAttribution) {
     FunctionDefinition(modifiers, name, arguments, block, native)
   }
 
+  private fun readLetDefinition(modifiers: DefinitionModifiers): LetDefinition = within {
+    val modifiers = readDefinitionModifiers()
+    expect(TokenType.Let)
+    val name = readSymbolRaw()
+    expect(TokenType.Equals)
+    val value = readExpression()
+    LetDefinition(modifiers, name, value)
+  }
+
   private fun maybeReadDefinition(): Definition? {
+    val modifiers = readDefinitionModifiers()
     val token = peek()
     return when (token.type) {
-      TokenType.Export,
+      TokenType.Func -> readFunctionDeclaration(modifiers)
-      TokenType.Func -> readFunctionDeclaration()
+      TokenType.Let -> readLetDefinition(modifiers)
       else -> null
     }
   }

parser/src/main/kotlin/gay/pizza/pork/parser/Printer.kt

@@ -91,6 +91,14 @@ class Printer(buffer: StringBuilder) : NodeVisitor<Unit> {
     visit(node.value)
   }
 
+  override fun visitLetDefinition(node: LetDefinition) {
+    visitDefinitionModifiers(node.modifiers)
+    append("let ")
+    visit(node.symbol)
+    append(" = ")
+    visit(node.value)
+  }
+
   override fun visitSymbolReference(node: SymbolReference) {
     visit(node.symbol)
   }
@@ -152,10 +160,14 @@ class Printer(buffer: StringBuilder) : NodeVisitor<Unit> {
     visit(node.right)
   }
 
-  override fun visitFunctionDefinition(node: FunctionDefinition) {
+  private fun visitDefinitionModifiers(modifiers: DefinitionModifiers) {
-    if (node.modifiers.export) {
+    if (modifiers.export) {
       append("export ")
     }
+  }
+
+  override fun visitFunctionDefinition(node: FunctionDefinition) {
+    visitDefinitionModifiers(node.modifiers)
     append("func ")
     visit(node.symbol)
     append("(")