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package coffee.liz.lambda;
import coffee.liz.lambda.parser.ArrowParser;
import coffee.liz.lambda.parser.LambdaParser;
import coffee.liz.lambda.parser.ParseException;
import coffee.liz.lambda.ast.Expression;
import coffee.liz.lambda.ast.LambdaProgram;
import coffee.liz.lambda.ast.Macro;
import coffee.liz.lambda.ast.SourceCode;
import coffee.liz.lambda.bind.ExternalBinding;
import coffee.liz.lambda.eval.Environment;
import coffee.liz.lambda.eval.NormalOrderEvaluator;
import coffee.liz.lambda.eval.Value;
import java.io.StringReader;
import java.util.List;
/**
* Entry point for parsing and interpreting lambda calculus programs.
*/
public class LambdaDriver {
/**
* Parses source code into an AST.
*
* @param sourceCode
* the source code (either Lambda or Arrow syntax)
* @return the parsed program
*/
public static LambdaProgram parse(final SourceCode sourceCode) {
return switch (sourceCode) {
case SourceCode.Lambda(String source) -> parseLambda(source);
case SourceCode.Arrow(String source) -> parseArrow(source);
};
}
private static LambdaProgram parseLambda(final String source) {
try (final StringReader reader = new StringReader(source)) {
return new LambdaParser(reader).Program();
} catch (final ParseException parseException) {
throw new RuntimeException("Failed to parse program", parseException);
}
}
private static LambdaProgram parseArrow(final String source) {
try (final StringReader reader = new StringReader(source)) {
return new ArrowParser(reader).Program();
} catch (final ParseException parseException) {
throw new RuntimeException("Failed to parse program", parseException);
}
}
/**
* Parses and evaluates lambda calculus programs.
*
* @param sourceCode
* the source code
* @return the evaluated result
*/
public static Value interpret(final SourceCode sourceCode) {
return interpret(sourceCode, List.of());
}
/**
* Parses and evaluates lambda calculus programs with "FFI"'s.
*
* @param sourceCode
* the source code
* @param bindings
* external Java functions available during evaluation
* @return the evaluated result
*/
public static Value interpret(final SourceCode sourceCode, final List<ExternalBinding> bindings) {
return interpret(sourceCode, bindings, Environment.root());
}
public static Value interpret(final SourceCode sourceCode, final List<ExternalBinding> bindings,
final Environment baseEnvironment) {
final LambdaProgram program = parse(sourceCode);
final Expression expression = program.expression();
final List<Macro> macros = program.macros();
return NormalOrderEvaluator.evaluate(expression, baseEnvironment.extend(Environment.from(macros, bindings)));
}
}
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