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package coffee.liz.lambda.parser;
import coffee.liz.lambda.LambdaDriver;
import coffee.liz.lambda.ast.Expression;
import coffee.liz.lambda.ast.Expression.AbstractionExpression;
import coffee.liz.lambda.ast.Expression.ApplicationExpression;
import coffee.liz.lambda.ast.Expression.IdentifierExpression;
import coffee.liz.lambda.ast.LambdaProgram;
import coffee.liz.lambda.ast.Macro;
import coffee.liz.lambda.ast.SourceCode;
import coffee.liz.lambda.ast.SourceComment;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertInstanceOf;
class ParserTest {
@Test
public void testTrivial() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("λx.x"));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("x -> x"));
assertStructurallyEqual(lambda, arrow);
assertEquals(0, lambda.macros().size());
assertInstanceOf(AbstractionExpression.class, lambda.expression());
assertEquals("x", ((AbstractionExpression) lambda.expression()).parameter());
}
@Test
public void testApplication() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("(λx.x) y"));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("(x -> x)(y)"));
assertStructurallyEqual(lambda, arrow);
final ApplicationExpression app = (ApplicationExpression) lambda.expression();
assertInstanceOf(AbstractionExpression.class, app.applicable());
assertInstanceOf(IdentifierExpression.class, app.argument());
}
@Test
public void testChainedLambdas() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("λx.λy.λz.x"));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("x -> y -> z -> x"));
assertStructurallyEqual(lambda, arrow);
final AbstractionExpression outer = (AbstractionExpression) lambda.expression();
assertEquals("x", outer.parameter());
final AbstractionExpression middle = (AbstractionExpression) outer.body();
assertEquals("y", middle.parameter());
final AbstractionExpression inner = (AbstractionExpression) middle.body();
assertEquals("z", inner.parameter());
}
@Test
public void testChainedApplication() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("((f x) y) z"));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("f(x)(y)(z)"));
assertStructurallyEqual(lambda, arrow);
final ApplicationExpression app1 = (ApplicationExpression) lambda.expression();
assertEquals("z", ((IdentifierExpression) app1.argument()).name());
final ApplicationExpression app2 = (ApplicationExpression) app1.applicable();
assertEquals("y", ((IdentifierExpression) app2.argument()).name());
final ApplicationExpression app3 = (ApplicationExpression) app2.applicable();
assertEquals("f", ((IdentifierExpression) app3.applicable()).name());
assertEquals("x", ((IdentifierExpression) app3.argument()).name());
}
@Test
public void testMacros() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("""
let id = λx.x;
id
"""));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("""
let id = x -> x;
id
"""));
assertStructurallyEqual(lambda, arrow);
assertEquals(1, lambda.macros().size());
assertEquals("id", lambda.macros().getFirst().name());
assertInstanceOf(IdentifierExpression.class, lambda.expression());
}
@Test
public void testLineComments() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("""
-- The identity function
let id = λx.x; -- returns its argument
id -- use it
"""));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("""
-- The identity function
let id = x -> x; -- returns its argument
id -- use it
"""));
assertStructurallyEqual(lambda, arrow);
assertEquals(1, lambda.macros().size());
assertEquals("id", lambda.macros().getFirst().name());
}
@Test
public void testComplexProgram() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("""
let zero = λf.λx.x;
let one = λf.λx.f x;
let succ = λn.λf.λx.f (n f x);
let add = λm.λn.λf.λx.m f (n f x);
succ (add one zero)
"""));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("""
let zero = f -> x -> x;
let one = f -> x -> f(x);
let succ = n -> f -> x -> f(n(f)(x));
let add = m -> n -> f -> x -> m(f)(n(f)(x));
succ(add(one)(zero))
"""));
assertStructurallyEqual(lambda, arrow);
assertEquals(4, lambda.macros().size());
assertEquals("zero", lambda.macros().get(0).name());
assertEquals("one", lambda.macros().get(1).name());
assertEquals("succ", lambda.macros().get(2).name());
assertEquals("add", lambda.macros().get(3).name());
}
@Test
public void testOmegaCombinator() {
final LambdaProgram lambda = LambdaDriver.parse(SourceCode.ofLambda("(λx.x x)(λx.x x)"));
final LambdaProgram arrow = LambdaDriver.parse(SourceCode.ofArrow("(x -> x(x))(x -> x(x))"));
assertStructurallyEqual(lambda, arrow);
}
private static void assertStructurallyEqual(final LambdaProgram expected, final LambdaProgram actual) {
assertEquals(expected.macros().size(), actual.macros().size(), "Macro count mismatch");
for (int i = 0; i < expected.macros().size(); i++) {
assertStructurallyEqual(expected.macros().get(i), actual.macros().get(i));
}
assertStructurallyEqual(expected.expression(), actual.expression());
}
private static void assertStructurallyEqual(final Macro expected, final Macro actual) {
assertEquals(expected.name(), actual.name(), "Macro name mismatch");
assertEquals(expected.comment().map(SourceComment::text), actual.comment().map(SourceComment::text),
"Macro comment mismatch");
assertStructurallyEqual(expected.expression(), actual.expression());
}
private static void assertStructurallyEqual(final Expression expected, final Expression actual) {
assertEquals(expected.getClass(), actual.getClass(), "Expression type mismatch");
assertEquals(expected.comment().map(SourceComment::text), actual.comment().map(SourceComment::text),
"Expression comment mismatch");
switch (expected) {
case IdentifierExpression e ->
assertEquals(e.name(), ((IdentifierExpression) actual).name(), "Identifier name mismatch");
case AbstractionExpression e -> {
assertEquals(e.parameter(), ((AbstractionExpression) actual).parameter(), "Parameter mismatch");
assertStructurallyEqual(e.body(), ((AbstractionExpression) actual).body());
}
case ApplicationExpression e -> {
assertStructurallyEqual(e.applicable(), ((ApplicationExpression) actual).applicable());
assertStructurallyEqual(e.argument(), ((ApplicationExpression) actual).argument());
}
}
}
}
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