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VisitorTest.java
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package hydra;
import hydra.core.FieldType;
import hydra.core.FloatType;
import hydra.core.IntegerType;
import hydra.core.LiteralType;
import hydra.core.Name;
import hydra.core.RowType;
import hydra.core.Type;
import hydra.core.WrappedType;
import java.util.Arrays;
import java.util.stream.Collectors;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertTrue;
/**
* This test illustrates constructing and visiting Hydra types using the generated visitor API.
*/
public class VisitorTest {
// A few example types
private final Type stringType = new Type.Literal(new LiteralType.String_());
private final Type int32Type = new Type.Literal(new LiteralType.Integer_(new IntegerType.Int32()));
private final Type float64Type = new Type.Literal(new LiteralType.Float_(new FloatType.Float64()));
private final Type listOfStrings = new Type.List(stringType);
private final Type maybeInt = new Type.Maybe(int32Type);
private final Type recordType = new Type.Record(new RowType(
new Name("LatLon"),
Arrays.asList(
new FieldType(new Name("lat"), float64Type),
new FieldType(new Name("lon"), float64Type))));
// Example visitor: format a type as a human-readable string
private final Type.Visitor<String> typeToString = new Type.Visitor<String>() {
@Override
public String visit(Type.Annotated instance) {
return instance.value.body.accept(typeToString) + " (annotated)";
}
@Override
public String visit(Type.Application instance) {
return "apply(" + instance.value.function.accept(typeToString)
+ ", " + instance.value.argument.accept(typeToString) + ")";
}
@Override
public String visit(Type.Either instance) {
return "either(" + instance.value.left.accept(typeToString)
+ ", " + instance.value.right.accept(typeToString) + ")";
}
@Override
public String visit(Type.Forall instance) {
return "forall " + instance.value.parameter.value + ". " + instance.value.body.accept(typeToString);
}
@Override
public String visit(Type.Function instance) {
return instance.value.domain.accept(typeToString) + " -> " + instance.value.codomain.accept(typeToString);
}
@Override
public String visit(Type.List instance) {
return "[" + instance.value.accept(typeToString) + "]";
}
@Override
public String visit(Type.Literal instance) {
return instance.value.accept(new LiteralType.Visitor<String>() {
@Override
public String visit(LiteralType.Binary instance) {
return "binary";
}
@Override
public String visit(LiteralType.Boolean_ instance) {
return "boolean";
}
@Override
public String visit(LiteralType.Float_ instance) {
return "float64";
}
@Override
public String visit(LiteralType.Integer_ instance) {
return "int32";
}
@Override
public String visit(LiteralType.String_ instance) {
return "string";
}
});
}
@Override
public String visit(Type.Map instance) {
return "map(" + instance.value.keys.accept(typeToString)
+ ", " + instance.value.values.accept(typeToString) + ")";
}
@Override
public String visit(Type.Maybe instance) {
return instance.value.accept(typeToString) + "?";
}
@Override
public String visit(Type.Pair instance) {
return "pair(" + instance.value.first.accept(typeToString)
+ ", " + instance.value.second.accept(typeToString) + ")";
}
@Override
public String visit(Type.Record instance) {
String fields = instance.value.fields.stream()
.map(f -> f.name.value + ": " + f.type.accept(typeToString))
.collect(Collectors.joining(", "));
return "{" + fields + "}";
}
@Override
public String visit(Type.Set instance) {
return "set(" + instance.value.accept(typeToString) + ")";
}
@Override
public String visit(Type.Union instance) {
String fields = instance.value.fields.stream()
.map(f -> f.name.value + ": " + f.type.accept(typeToString))
.collect(Collectors.joining(" | "));
return "(" + fields + ")";
}
@Override
public String visit(Type.Unit instance) {
return "unit";
}
@Override
public String visit(Type.Variable instance) {
return instance.value.value;
}
@Override
public String visit(Type.Wrap instance) {
return "wrap(" + instance.value.typeName.value + ", " + instance.value.body.accept(typeToString) + ")";
}
};
// Example partial visitor: check whether a type is a numeric literal type
private final Type.PartialVisitor<Boolean> isNumericType = new Type.PartialVisitor<Boolean>() {
@Override
public Boolean visit(Type.Literal instance) {
return instance.value.accept(new LiteralType.PartialVisitor<Boolean>() {
@Override
public Boolean visit(LiteralType.Float_ instance) {
return true;
}
@Override
public Boolean visit(LiteralType.Integer_ instance) {
return true;
}
@Override
public Boolean otherwise(LiteralType ignored) {
return false;
}
});
}
@Override
public Boolean otherwise(Type instance) {
return false;
}
};
@Test
public void demonstrateVisitor() {
assertEquals("string", stringType.accept(typeToString));
assertEquals("int32", int32Type.accept(typeToString));
assertEquals("[string]", listOfStrings.accept(typeToString));
assertEquals("int32?", maybeInt.accept(typeToString));
assertEquals("{lat: float64, lon: float64}", recordType.accept(typeToString));
}
@Test
public void demonstratePartialVisitor() {
assertFalse(stringType.accept(isNumericType));
assertTrue(int32Type.accept(isNumericType));
assertTrue(float64Type.accept(isNumericType));
assertFalse(listOfStrings.accept(isNumericType));
assertFalse(recordType.accept(isNumericType));
}
}