Add tuples.

12 files changed, 110 insertions, 35 deletions

diff --git a/ast/src/main/java/lv/enes/orang/ast/EmptyTupleLiteral.java b/ast/src/main/java/lv/enes/orang/ast/EmptyTupleLiteral.java
new file mode 100644
index 0000000..a96580f
--- /dev/null
+++ b/ast/src/main/java/lv/enes/orang/ast/EmptyTupleLiteral.java
@@ -0,0 +1,14 @@
+package lv.enes.orang.ast;
+
+import lv.enes.orang.core.OrangException;
+
+public final class EmptyTupleLiteral implements Expression {
+        public static final EmptyTupleLiteral INSTANCE = new EmptyTupleLiteral();
+
+        private EmptyTupleLiteral() {}
+
+        @Override
+        public <R, E extends OrangException> R accept(ExpressionVisitor<R, E> visitor) throws E {
+                return visitor.visitEmptyTupleExpression();
+        }
+}
diff --git a/ast/src/main/java/lv/enes/orang/ast/ExpressionVisitor.java b/ast/src/main/java/lv/enes/orang/ast/ExpressionVisitor.java
index 70f8a5e..c32b429 100644
--- a/ast/src/main/java/lv/enes/orang/ast/ExpressionVisitor.java
+++ b/ast/src/main/java/lv/enes/orang/ast/ExpressionVisitor.java
@@ -12,12 +12,13 @@ public interface ExpressionVisitor<R, E extends OrangException> {
         R visitBinaryExpression(BinaryExpression expr) throws E;
         R visitCallExpression(CallExpression expr) throws E;
         R visitDoExpression(DoExpression expr) throws E;
+        R visitEmptyTupleExpression() throws E;
         R visitFnExpression(FnExpression expr) throws E;
         R visitIfElseExpression(IfElseExpression expr) throws E;
         R visitIntLiteral(IntLiteral expr) throws E;
         R visitLetInExpression(LetInExpression expr) throws E;
         R visitStringLiteral(StringLiteral expr) throws E;
+        R visitTupleExpression(TupleExpression expr) throws E;
         R visitUnaryExpression(UnaryExpression expr) throws E;
         R visitVariable(VariableExpression expr) throws E;
-        R visitVoidExpression() throws E;
 }
diff --git a/ast/src/main/java/lv/enes/orang/ast/TupleExpression.java b/ast/src/main/java/lv/enes/orang/ast/TupleExpression.java
new file mode 100644
index 0000000..9df418d
--- /dev/null
+++ b/ast/src/main/java/lv/enes/orang/ast/TupleExpression.java
@@ -0,0 +1,13 @@
+package lv.enes.orang.ast;
+
+import lv.enes.orang.core.OrangException;
+import lv.enes.orang.utils.NonEmptyList;
+
+public record TupleExpression(NonEmptyList<Expression> children) implements Expression {
+        // assert children.size() >= 2
+
+        @Override
+        public <R, E extends OrangException> R accept(ExpressionVisitor<R, E> visitor) throws E {
+                return visitor.visitTupleExpression(this);
+        }
+}
diff --git a/ast/src/main/java/lv/enes/orang/ast/VoidExpression.java b/ast/src/main/java/lv/enes/orang/ast/VoidExpression.java
deleted file mode 100644
index 39d164d..0000000
--- a/ast/src/main/java/lv/enes/orang/ast/VoidExpression.java
+++ /dev/null
@@ -1,14 +0,0 @@
-package lv.enes.orang.ast;
-
-import lv.enes.orang.core.OrangException;
-
-public final class VoidExpression implements Expression {
-        public static final VoidExpression INSTANCE = new VoidExpression();
-
-        private VoidExpression() {}
-
-        @Override
-        public <R, E extends OrangException> R accept(ExpressionVisitor<R, E> visitor) throws E {
-                return visitor.visitVoidExpression();
-        }
-}
diff --git a/checker/src/main/java/lv/enes/orang/checker/Checker.java b/checker/src/main/java/lv/enes/orang/checker/Checker.java
index e15fab9..66b7dac 100644
--- a/checker/src/main/java/lv/enes/orang/checker/Checker.java
+++ b/checker/src/main/java/lv/enes/orang/checker/Checker.java
@@ -65,6 +65,12 @@ public class Checker implements ExpressionVisitor<Void, CheckerException>, State
         }
 
         @Override
+        public Void visitEmptyTupleExpression() {
+                // Always ok
+                return null;
+        }
+
+        @Override
         public Checker visitExpression(ExpressionStatement expr) throws CheckerException {
                 visit(expr.expr());
                 return this;
@@ -122,6 +128,14 @@ public class Checker implements ExpressionVisitor<Void, CheckerException>, State
         }
 
         @Override
+        public Void visitTupleExpression(TupleExpression expr) throws CheckerException {
+                for (var child : expr.children()) {
+                        visit(child);
+                }
+                return null;
+        }
+
+        @Override
         public Void visitUnaryExpression(UnaryExpression expr) throws CheckerException {
                 visit(expr.child());
                 return null;
@@ -134,10 +148,4 @@ public class Checker implements ExpressionVisitor<Void, CheckerException>, State
                 }
                 return null;
         }
-
-        @Override
-        public Void visitVoidExpression() {
-                // Always ok
-                return null;
-        }
 }
diff --git a/evaluator/src/main/java/lv/enes/orang/evaluator/Nothing.java b/evaluator/src/main/java/lv/enes/orang/evaluator/EmptyTuple.java
index c971649..f8e043b 100644
--- a/evaluator/src/main/java/lv/enes/orang/evaluator/Nothing.java
+++ b/evaluator/src/main/java/lv/enes/orang/evaluator/EmptyTuple.java
@@ -3,10 +3,10 @@ package lv.enes.orang.evaluator;
 import lombok.EqualsAndHashCode;
 
 @EqualsAndHashCode
-public final class Nothing implements Value {
-        public static final Nothing INSTANCE = new Nothing();
+public final class EmptyTuple implements Value {
+        public static final EmptyTuple INSTANCE = new EmptyTuple();
 
-        private Nothing() {
+        private EmptyTuple() {
         }
 
         @Override
diff --git a/evaluator/src/main/java/lv/enes/orang/evaluator/Evaluator.java b/evaluator/src/main/java/lv/enes/orang/evaluator/Evaluator.java
index 6925bac..f0299b4 100644
--- a/evaluator/src/main/java/lv/enes/orang/evaluator/Evaluator.java
+++ b/evaluator/src/main/java/lv/enes/orang/evaluator/Evaluator.java
@@ -2,6 +2,7 @@ package lv.enes.orang.evaluator;
 
 import lv.enes.orang.ast.*;
 import lv.enes.orang.core.OrangRuntimeException;
+import lv.enes.orang.utils.NonEmptyList;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -71,6 +72,11 @@ public record Evaluator(Map<String, Value> scope, Value lastResult) implements E
         }
 
         @Override
+        public Value visitEmptyTupleExpression() {
+                return EmptyTuple.INSTANCE;
+        }
+
+        @Override
         public Evaluator visitExpression(ExpressionStatement expr) throws OrangRuntimeException {
                 return new Evaluator(this.scope(), visit(expr.expr()));
         }
@@ -122,6 +128,11 @@ public record Evaluator(Map<String, Value> scope, Value lastResult) implements E
         }
 
         @Override
+        public Value visitStringLiteral(StringLiteral expr) {
+                return new OrangString(expr.value());
+        }
+
+        @Override
         public Value visitUnaryExpression(UnaryExpression expr) throws OrangRuntimeException {
                 var child = visit(expr.child());
                 return switch (expr.operator()) {
@@ -132,8 +143,12 @@ public record Evaluator(Map<String, Value> scope, Value lastResult) implements E
         }
 
         @Override
-        public Value visitStringLiteral(StringLiteral expr) {
-                return new OrangString(expr.value());
+        public Value visitTupleExpression(TupleExpression expr) throws OrangRuntimeException {
+                var values = new ArrayList<Value>();
+                for (var tailExpr : expr.children()) {
+                        values.add(visit(tailExpr));
+                }
+                return new Tuple(new NonEmptyList<>(values));
         }
 
         @Override
@@ -144,9 +159,4 @@ public record Evaluator(Map<String, Value> scope, Value lastResult) implements E
 
                 throw new OrangRuntimeException(STR."Value named \{expr.name()} is not defined!");
         }
-
-        @Override
-        public Value visitVoidExpression() {
-                return Nothing.INSTANCE;
-        }
 }
diff --git a/evaluator/src/main/java/lv/enes/orang/evaluator/PartialFunction.java b/evaluator/src/main/java/lv/enes/orang/evaluator/PartialFunction.java
index d0125f6..7c0ca20 100644
--- a/evaluator/src/main/java/lv/enes/orang/evaluator/PartialFunction.java
+++ b/evaluator/src/main/java/lv/enes/orang/evaluator/PartialFunction.java
@@ -15,7 +15,7 @@ public record PartialFunction(Map<String, Value> scope, NonEmptyList<ArgSpec> re
                 switch (spec.getType()) {
                         case NAMED -> newScope.put(((ArgSpec.Named)spec).name(), param);
                         case NOTHING -> {
-                                if (!(param instanceof Nothing)) {
+                                if (!(param instanceof EmptyTuple)) {
                                         throw new OrangRuntimeException(STR."Expected () as a parameter but got \{param.typeName()}");
                                 }
                         }
diff --git a/evaluator/src/main/java/lv/enes/orang/evaluator/Tuple.java b/evaluator/src/main/java/lv/enes/orang/evaluator/Tuple.java
new file mode 100644
index 0000000..d5a1df5
--- /dev/null
+++ b/evaluator/src/main/java/lv/enes/orang/evaluator/Tuple.java
@@ -0,0 +1,25 @@
+package lv.enes.orang.evaluator;
+
+import lv.enes.orang.utils.NonEmptyList;
+
+public record Tuple(NonEmptyList<Value> contents) implements Value {
+        @Override
+        public String typeName() {
+                var sb = new StringBuilder("(");
+                sb.append(contents.getFirst().typeName());
+                for (var i = 1; i < contents.size(); i++) {
+                        sb.append(", ").append(contents.get(i).typeName());
+                }
+                return sb.append(")").toString();
+        }
+
+        @Override
+        public String stringify() {
+                var sb = new StringBuilder("(");
+                sb.append(contents.getFirst().stringify());
+                for (var i = 1; i < contents.size(); i++) {
+                        sb.append(", ").append(contents.get(i).stringify());
+                }
+                return sb.append(")").toString();
+        }
+}
diff --git a/evaluator/src/main/java/lv/enes/orang/evaluator/Value.java b/evaluator/src/main/java/lv/enes/orang/evaluator/Value.java
index d8c8b9c..2ef5136 100644
--- a/evaluator/src/main/java/lv/enes/orang/evaluator/Value.java
+++ b/evaluator/src/main/java/lv/enes/orang/evaluator/Value.java
@@ -3,7 +3,8 @@ package lv.enes.orang.evaluator;
 import lv.enes.orang.core.OrangRuntimeException;
 
 public sealed interface Value
-                permits Array, BuiltinFunction, Function, Nothing, OrangBoolean, OrangInteger, OrangString, PartialBuiltinFunction, PartialFunction, Undefined {
+                permits Array, BuiltinFunction, EmptyTuple, Function, OrangBoolean, OrangInteger, OrangString,
+                PartialBuiltinFunction, PartialFunction, Tuple, Undefined {
         String typeName();
         String stringify();
 
diff --git a/grammar.bnf b/grammar.bnf
index a9e21cb..8715ad2 100644
--- a/grammar.bnf
+++ b/grammar.bnf
@@ -14,17 +14,21 @@ binop ::= '*' | '/' | '+' | '-' | '?=' | '/=' | '>' | '>=' | '<' | '<=';
 unop ::= '+' | '-' | '!';
 simple-expression ::= '(' expression ')'
                     | 'true' | 'false'
-                    | '(' ')'
                     | INTEGER
                     | IDENTIFIER
                     | STRING
                     | array
+                    | tuple
                     | if-else-expression
                     | let-in-expression
                     | fn-expression
                     | do-expression;
 
 array ::= '[' ']' | '[' expression (',' expression)* ','? ']';
+// Note that tuples always have either zero or at least two elements
+// A tuple with only one element is just '(' expression ')' -- a parenthese-wrapped expression
+// Also '(' expression ',' ')' is illegal
+tuple ::= '(' ')' | '(' expression ',' expression (',' expression)* ','? ')';
 
 if-else-expression ::= 'if' expression 'then' expression 'else' expression;
 let-in-expression ::= 'let' def-spec '=' expression ('and' def-spec '=' expression)* 'in' expression;
diff --git a/parser/src/main/java/lv/enes/orang/parser/Parser.java b/parser/src/main/java/lv/enes/orang/parser/Parser.java
index 25b57d4..0ff1f78 100644
--- a/parser/src/main/java/lv/enes/orang/parser/Parser.java
+++ b/parser/src/main/java/lv/enes/orang/parser/Parser.java
@@ -283,9 +283,12 @@ public class Parser {
                         case PAREN_LEFT -> {
                                 consumeToken(Token.Type.PAREN_LEFT);
                                 if (maybeConsumeToken(Token.Type.PAREN_RIGHT)) {
-                                        yield VoidExpression.INSTANCE;
+                                        yield EmptyTupleLiteral.INSTANCE;
                                 }
                                 var expr = parseExpression();
+                                if (maybeConsumeToken(Token.Type.COMMA)) {
+                                        yield parseTupleExpression(expr);
+                                }
                                 consumeToken(Token.Type.PAREN_RIGHT);
                                 yield expr;
                         }
@@ -336,6 +339,16 @@ public class Parser {
                 return new StringLiteral(sb.toString());
         }
 
+        private TupleExpression parseTupleExpression(Expression first) throws ParserException {
+                var exprs = new ArrayList<Expression>();
+                exprs.add(first);
+                do {
+                        exprs.add(parseExpression());
+                        maybeConsumeToken(Token.Type.COMMA);
+                } while (!maybeConsumeToken(Token.Type.PAREN_RIGHT));
+                return new TupleExpression(new NonEmptyList<>(exprs));
+        }
+
         private Expression parseUnaryExpression() throws ParserException {
                 if (isUnaryOp(input.peek())) {
                         var op = toUnaryOp(input.next());