Use parser example for integration tests

examples/parser/ast.elk

@@ -2,4 +2,6 @@ pub struct Token(kind, value)
 
 pub struct BinaryExpr(left, op, right)
 
-pub struct LiteralExpr(value)
+pub struct LiteralExpr(value)
+
+pub struct GroupExpr(value)

examples/parser/evaluator.elk

@@ -7,6 +7,7 @@ pub fn evaluate(ast) {
 fn next(expr) {
     return nextBinary(expr) if expr | isType(BinaryExpr)
     return nextLiteral(expr) if expr | isType(LiteralExpr)
+    return nextGroup(expr) if expr | isType(GroupExpr)
 }
 
 fn nextBinary(expr) {
@@ -21,4 +22,8 @@ fn nextBinary(expr) {
 
 fn nextLiteral(expr) {
     expr->value->value | into::float
+}
+
+fn nextGroup(expr) {
+    expr->value | next
 }

examples/parser/lexer.elk

@@ -30,7 +30,7 @@ fn next() {
 
     return nil if c == nil
 
-    if c in ["+", "-", "*", "/"] {
+    if c in ["+", "-", "*", "/", "(", ")"] {
         advance
         return new Token(c, c)
     }

examples/parser/parser.elk

@@ -8,6 +8,7 @@ let index = 0
 pub fn parse(input) {
     tokens = lexer::lex(input)
     index = 0
+    return nil if len(tokens) == 0
 
     expr()
 }
@@ -28,6 +29,13 @@ fn match(kinds...) {
     kinds | iter::anyOf => kind { kind == current()->kind }
 }
 
+fn expect(kind) {
+    return advance() if match(kind)
+
+    throw new ParseError("Expected '${kind}'") if current() == nil
+    throw new ParseError("Expected '${kind}' but got '${current()->kind}'")
+}
+
 fn expr() {
     additive()
 }
@@ -61,6 +69,13 @@ fn primary() {
         return new LiteralExpr(advance())
     }
 
+    if match("(") {
+        advance()
+        let group = new GroupExpr(expr())
+        expect(")")
+        return group
+    }
+
     throw new ParseError("Unexpected end of expression") if current() != nil
     throw new ParseError("Unexpected token: '${current()->kind}'")
 }

examples/parser/tests.elk

@@ -0,0 +1,7 @@
+with parse from ./parser
+with evaluate from ./evaluator
+
+parse("2 + 3 * 4") | evaluate | assertEqual(14)
+parse("(3 + 3 * 4) / 3") | evaluate | assertEqual(5)
+parse("2") | evaluate | assertEqual(2)
+parse("") | evaluate | assertEqual(nil)

tests/IntegrationTests.cs

@@ -46,6 +46,7 @@ public static IEnumerable<string> ElkFiles()
             Directory.GetFiles(dataPath, "*.elk", SearchOption.AllDirectories),
             Directory.GetFiles(Path.Combine(examplesPath, "advent-of-code-2022"), "*.elk", SearchOption.AllDirectories),
             Directory.GetFiles(Path.Combine(examplesPath, "advent-of-code-2023"), "*.elk", SearchOption.AllDirectories),
+            Directory.GetFiles(Path.Combine(examplesPath, "parser"), "*.elk", SearchOption.AllDirectories),
         }.SelectMany(x => x);
     }
 }