package io.jawk.intermediate;
   
   /*-
    * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
    * Jawk
    * ჻჻჻჻჻჻
    * Copyright (C) 2006 - 2026 MetricsHub
    * ჻჻჻჻჻჻
    * This program is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Lesser General Public License as
   * published by the Free Software Foundation, either version 3 of the
   * License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Lesser Public License for more details.
   *
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-3.0.html>.
   * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
   */
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.function.Supplier;
  import java.util.regex.Pattern;
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import io.jawk.ext.ExtensionFunction;
  
  /**
   * Represents one instruction in the tuple stream produced by {@link AwkTuples}.
   * Concrete subclasses carry only the operands required by their opcode or opcode
   * group.
   *
   * @author Danny Daglas
   * @see AwkTuples
   */
  public abstract class Tuple implements Serializable {
  
  	private static final long serialVersionUID = 8105941219003992817L;
  	private final Opcode opcode;
  	private int lineNumber = -1;
  	private Tuple next = null;
  
  	Tuple(Opcode opcode) {
  		this.opcode = opcode;
  	}
  
  	/**
  	 * Returns this tuple's opcode.
  	 *
  	 * @return opcode executed by the AVM
  	 */
  	public final Opcode getOpcode() {
  		return opcode;
  	}
  
  	/**
  	 * Returns this tuple's jump/call address, if it has one.
  	 *
  	 * @return tuple address, or {@code null}
  	 */
  	public Address getAddress() {
  		return null;
  	}
  
  	/**
  	 * Returns every jump/call address carried by this tuple.
  	 *
  	 * @return tuple addresses, or an empty list
  	 */
  	public List<Address> getAddresses() {
  		Address address = getAddress();
  		if (address == null) {
  			return Collections.emptyList();
  		}
  		return Collections.singletonList(address);
  	}
  
  	/**
  	 * Resolves deferred operands and validates resolved addresses.
  	 *
  	 * @param queue tuple queue used to validate address targets
  	 */
  	public void touch(List<Tuple> queue) {
  		for (Address address : getAddresses()) {
  			if (address.index() == -1) {
  				throw new Error("address " + address + " is unresolved");
  			}
  			if (address.index() >= queue.size()) {
  				throw new Error("address " + address + " doesn't resolve to an actual list element");
  			}
 		}
 	}
 
 	boolean hasNext() {
 		return next != null;
 	}
 
 	/**
 	 * Returns the next tuple in execution order.
 	 *
 	 * @return next tuple, or {@code null} at the end of the stream
 	 */
 	Tuple getNext() {
 		return next;
 	}
 
 	void setNext(Tuple next) {
 		this.next = next;
 	}
 
 	void setLineNumber(int lineNumber) {
 		this.lineNumber = lineNumber;
 	}
 
 	/**
 	 * Returns the source line number associated with this tuple.
 	 *
 	 * @return source line number, or {@code -1} when unknown
 	 */
 	public int getLineNumber() {
 		return lineNumber;
 	}
 
 	private static String stringArgument(String value) {
 		return ", \"" + value + '"';
 	}
 
 	private static String patternArgument(Pattern pattern) {
 		return ", /" + (pattern == null ? "" : pattern.pattern()) + '/';
 	}
 
 	/**
 	 * Tuple for opcodes without operands.
 	 */
 	public static class NoOperandTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 
 		NoOperandTuple(Opcode opcode) {
 			super(opcode);
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name();
 		}
 	}
 
 	/**
 	 * Tuple for discarding an expression-statement value after validating that it
 	 * is scalar.
 	 */
 	public static final class ScalarPopTuple extends NoOperandTuple {
 		private static final long serialVersionUID = 1L;
 
 		ScalarPopTuple() {
 			super(Opcode.POP);
 		}
 	}
 
 	/**
 	 * Tuple for JRT-managed built-in variable operations.
 	 */
 	public static final class BuiltinVarTuple extends NoOperandTuple {
 		private static final long serialVersionUID = 1L;
 
 		BuiltinVarTuple(Opcode opcode) {
 			super(opcode);
 		}
 	}
 
 	/**
 	 * Tuple for a long literal.
 	 */
 	public static final class PushLongTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final long value;
 
 		PushLongTuple(long value) {
 			super(Opcode.PUSH_LONG);
 			this.value = value;
 		}
 
 		/**
 		 * Returns the literal value.
 		 *
 		 * @return literal long value
 		 */
 		public long getValue() {
 			return value;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + value;
 		}
 	}
 
 	/**
 	 * Tuple for a double literal.
 	 */
 	public static final class PushDoubleTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final double value;
 
 		PushDoubleTuple(double value) {
 			super(Opcode.PUSH_DOUBLE);
 			this.value = value;
 		}
 
 		/**
 		 * Returns the literal value.
 		 *
 		 * @return literal double value
 		 */
 		public double getValue() {
 			return value;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + value;
 		}
 	}
 
 	/**
 	 * Tuple for a string literal.
 	 */
 	public static final class PushStringTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final String value;
 
 		PushStringTuple(String value) {
 			super(Opcode.PUSH_STRING);
 			this.value = value;
 		}
 
 		/**
 		 * Returns the literal value.
 		 *
 		 * @return literal string value
 		 */
 		public String getValue() {
 			return value;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + stringArgument(value);
 		}
 	}
 
 	/**
 	 * Tuple for opcodes whose single operand is a count.
 	 */
 	public static class CountTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final long count;
 
 		CountTuple(Opcode opcode, long count) {
 			super(opcode);
 			this.count = count;
 		}
 
 		/**
 		 * Returns the tuple count operand.
 		 *
 		 * @return count operand
 		 */
 		public final long getCount() {
 			return count;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + count;
 		}
 	}
 
 	/**
 	 * Tuple for print/printf redirection with an append flag.
 	 */
 	public static final class CountAndAppendTuple extends CountTuple {
 		private static final long serialVersionUID = 1L;
 		private final boolean append;
 
 		CountAndAppendTuple(Opcode opcode, long count, boolean append) {
 			super(opcode, count);
 			this.append = append;
 		}
 
 		/**
 		 * Indicates whether redirected output should append.
 		 *
 		 * @return {@code true} for append mode
 		 */
 		public boolean isAppend() {
 			return append;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + getCount() + ", " + append;
 		}
 	}
 
 	/**
 	 * Tuple for a long operand that is not interpreted by the tuple itself.
 	 */
 	public static class LongTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final long value;
 
 		LongTuple(Opcode opcode, long value) {
 			super(opcode);
 			this.value = value;
 		}
 
 		/**
 		 * Returns the long operand.
 		 *
 		 * @return long operand
 		 */
 		public final long getValue() {
 			return value;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + value;
 		}
 	}
 
 	/**
 	 * Tuple for a constant input-field index.
 	 */
 	public static final class InputFieldTuple extends LongTuple {
 		private static final long serialVersionUID = 1L;
 
 		InputFieldTuple(long fieldIndex) {
 			super(Opcode.GET_INPUT_FIELD_CONST, fieldIndex);
 		}
 
 		/**
 		 * Returns the constant input-field index.
 		 *
 		 * @return input-field index
 		 */
 		public long getFieldIndex() {
 			return getValue();
 		}
 	}
 
 	/**
 	 * Tuple for an address operand.
 	 */
 	public static class AddressTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private Address address;
 
 		AddressTuple(Opcode opcode, Address address) {
 			super(opcode);
 			this.address = address;
 		}
 
 		@Override
 		public Address getAddress() {
 			return address;
 		}
 
 		void setAddress(Address address) {
 			this.address = address;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + address;
 		}
 	}
 
 	/**
 	 * Tuple for variable offset/global operands.
 	 */
 	public static class VariableTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final long variableOffset;
 		private final boolean global;
 
 		VariableTuple(Opcode opcode, long variableOffset, boolean global) {
 			super(opcode);
 			this.variableOffset = variableOffset;
 			this.global = global;
 		}
 
 		/**
 		 * Returns the variable offset.
 		 *
 		 * @return variable offset
 		 */
 		public final long getVariableOffset() {
 			return variableOffset;
 		}
 
 		/**
 		 * Indicates whether the variable offset belongs to the global frame.
 		 *
 		 * @return {@code true} for a global variable
 		 */
 		public final boolean isGlobal() {
 			return global;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + variableOffset + ", " + global;
 		}
 	}
 
 	/**
 	 * Tuple for scalar compound assignments.
 	 */
 	public static final class CompoundAssignTuple extends VariableTuple {
 		private static final long serialVersionUID = 1L;
 
 		CompoundAssignTuple(Opcode opcode, long variableOffset, boolean global) {
 			super(opcode, variableOffset, global);
 		}
 	}
 
 	/**
 	 * Tuple for array compound assignments.
 	 */
 	public static final class CompoundAssignArrayTuple extends VariableTuple {
 		private static final long serialVersionUID = 1L;
 
 		CompoundAssignArrayTuple(Opcode opcode, long variableOffset, boolean global) {
 			super(opcode, variableOffset, global);
 		}
 	}
 
 	/**
 	 * Tuple for stack-provided map element compound assignments.
 	 */
 	public static final class CompoundAssignMapElementTuple extends NoOperandTuple {
 		private static final long serialVersionUID = 1L;
 
 		CompoundAssignMapElementTuple(Opcode opcode) {
 			super(opcode);
 		}
 	}
 
 	/**
 	 * Tuple for input-field compound assignments.
 	 */
 	public static final class CompoundAssignInputFieldTuple extends NoOperandTuple {
 		private static final long serialVersionUID = 1L;
 
 		CompoundAssignInputFieldTuple(Opcode opcode) {
 			super(opcode);
 		}
 	}
 
 	/**
 	 * Tuple for variable dereference.
 	 */
 	public static final class DereferenceTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final long variableOffset;
 		private final boolean array;
 		private final boolean global;
 
 		DereferenceTuple(long variableOffset, boolean array, boolean global) {
 			super(Opcode.DEREFERENCE);
 			this.variableOffset = variableOffset;
 			this.array = array;
 			this.global = global;
 		}
 
 		/**
 		 * Returns the variable offset.
 		 *
 		 * @return variable offset
 		 */
 		public long getVariableOffset() {
 			return variableOffset;
 		}
 
 		/**
 		 * Indicates whether this dereference should initialize an array.
 		 *
 		 * @return {@code true} when the variable is an array
 		 */
 		public boolean isArray() {
 			return array;
 		}
 
 		/**
 		 * Indicates whether the variable offset belongs to the global frame.
 		 *
 		 * @return {@code true} for a global variable
 		 */
 		public boolean isGlobal() {
 			return global;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + variableOffset + ", " + array + ", " + global;
 		}
 	}
 
 	/**
 	 * Tuple for boolean operands.
 	 */
 	public static final class BooleanTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final boolean value;
 
 		BooleanTuple(Opcode opcode, boolean value) {
 			super(opcode);
 			this.value = value;
 		}
 
 		/**
 		 * Returns the boolean operand.
 		 *
 		 * @return boolean operand
 		 */
 		public boolean getValue() {
 			return value;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + value;
 		}
 	}
 
 	/**
 	 * Tuple for sub/gsub against variable-backed values.
 	 */
 	public static final class SubstitutionVariableTuple extends VariableTuple {
 		private static final long serialVersionUID = 1L;
 		private final boolean globalSubstitution;
 
 		SubstitutionVariableTuple(Opcode opcode, long variableOffset, boolean global, boolean globalSubstitution) {
 			super(opcode, variableOffset, global);
 			this.globalSubstitution = globalSubstitution;
 		}
 
 		/**
 		 * Indicates whether this substitution is global.
 		 *
 		 * @return {@code true} for {@code gsub}, {@code false} for {@code sub}
 		 */
 		public boolean isGlobalSubstitution() {
 			return globalSubstitution;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + getVariableOffset() + ", " + isGlobal() + ", " + globalSubstitution;
 		}
 	}
 
 	/**
 	 * Tuple for a precompiled literal regular expression.
 	 */
 	public static final class RegexTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final String regex;
 		private final Pattern pattern;
 
 		RegexTuple(String regex, Pattern pattern) {
 			super(Opcode.REGEXP);
 			this.regex = regex;
 			this.pattern = pattern;
 		}
 
 		/**
 		 * Returns the original regular expression text.
 		 *
 		 * @return regular expression text
 		 */
 		public String getRegex() {
 			return regex;
 		}
 
 		/**
 		 * Returns the precompiled regular expression.
 		 *
 		 * @return compiled pattern
 		 */
 		public Pattern getPattern() {
 			return pattern;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + stringArgument(regex) + patternArgument(pattern);
 		}
 	}
 
 	/**
 	 * Tuple for a class check.
 	 */
 	public static final class ClassTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final Class<?> type;
 
 		ClassTuple(Class<?> type) {
 			super(Opcode.CHECK_CLASS);
 			this.type = type;
 		}
 
 		/**
 		 * Returns the required runtime type.
 		 *
 		 * @return required class
 		 */
 		public Class<?> getType() {
 			return type;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + type;
 		}
 	}
 
 	/**
 	 * Tuple for function definitions.
 	 */
 	public static final class FunctionTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final String functionName;
 		private final long numFormalParams;
 
 		FunctionTuple(String functionName, long numFormalParams) {
 			super(Opcode.FUNCTION);
 			this.functionName = functionName;
 			this.numFormalParams = numFormalParams;
 		}
 
 		/**
 		 * Returns the function name.
 		 *
 		 * @return function name
 		 */
 		public String getFunctionName() {
 			return functionName;
 		}
 
 		/**
 		 * Returns the number of formal parameters.
 		 *
 		 * @return formal parameter count
 		 */
 		public long getNumFormalParams() {
 			return numFormalParams;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + stringArgument(functionName) + ", " + numFormalParams;
 		}
 	}
 
 	/**
 	 * Tuple for function calls.
 	 */
 	public static final class CallFunctionTuple extends AddressTuple {
 		private static final long serialVersionUID = 1L;
 		private transient Supplier<Address> addressSupplier;
 		private final String functionName;
 		private final long numFormalParams;
 		private final long numActualParams;
 
 		CallFunctionTuple(
 				Supplier<Address> addressSupplier,
 				String functionName,
 				long numFormalParams,
 				long numActualParams) {
 			super(Opcode.CALL_FUNCTION, null);
 			this.addressSupplier = addressSupplier;
 			this.functionName = functionName;
 			this.numFormalParams = numFormalParams;
 			this.numActualParams = numActualParams;
 		}
 
 		@Override
 		public Address getAddress() {
 			Address address = super.getAddress();
 			if (address == null && addressSupplier != null) {
 				address = addressSupplier.get();
 				setAddress(address);
 				addressSupplier = null;
 			}
 			return address;
 		}
 
 		@Override
 		public void touch(List<Tuple> queue) {
 			getAddress();
 			super.touch(queue);
 		}
 
 		/**
 		 * Returns the function name.
 		 *
 		 * @return function name
 		 */
 		public String getFunctionName() {
 			return functionName;
 		}
 
 		/**
 		 * Returns the number of formal parameters.
 		 *
 		 * @return formal parameter count
 		 */
 		public long getNumFormalParams() {
 			return numFormalParams;
 		}
 
 		/**
 		 * Returns the number of actual parameters at this call site.
 		 *
 		 * @return actual parameter count
 		 */
 		public long getNumActualParams() {
 			return numActualParams;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name()
 					+ ", "
 					+ getAddress()
 					+ stringArgument(functionName)
 					+ ", "
 					+ numFormalParams
 					+ ", "
 					+ numActualParams;
 		}
 	}
 
 	/**
 	 * Runtime target metadata for a user-defined indirect function call.
 	 */
 	public static final class IndirectFunctionTarget implements Serializable {
 		private static final long serialVersionUID = 1L;
 		private transient Supplier<Address> addressSupplier;
 		private Address address;
 		private final long numFormalParams;
 		private final Set<Integer> arrayParameterIndexes;
 
 		/**
 		 * Creates target metadata whose address is resolved during tuple
 		 * post-processing.
 		 *
 		 * @param addressSupplierParam function entry-point supplier
 		 * @param numFormalParamsParam formal parameter count
 		 * @param arrayParameterIndexesParam zero-based array parameter indexes
 		 */
 		public IndirectFunctionTarget(
 				Supplier<Address> addressSupplierParam,
 				long numFormalParamsParam,
 				Set<Integer> arrayParameterIndexesParam) {
 			addressSupplier = addressSupplierParam;
 			numFormalParams = numFormalParamsParam;
 			arrayParameterIndexes = Collections.unmodifiableSet(new HashSet<Integer>(arrayParameterIndexesParam));
 		}
 
 		private void resolve() {
 			if (address == null && addressSupplier != null) {
 				address = addressSupplier.get();
 				addressSupplier = null;
 			}
 		}
 
 		/**
 		 * Returns the resolved function entry point.
 		 *
 		 * @return function address
 		 */
 		public Address getAddress() {
 			resolve();
 			return address;
 		}
 
 		/**
 		 * Returns the function's formal parameter count.
 		 *
 		 * @return formal parameter count
 		 */
 		public long getNumFormalParams() {
 			return numFormalParams;
 		}
 
 		/**
 		 * Returns whether the parameter at the supplied index is an array.
 		 *
 		 * @param index zero-based formal parameter index
 		 * @return {@code true} when the formal parameter is an array
 		 */
 		public boolean isArrayParameter(int index) {
 			return arrayParameterIndexes.contains(Integer.valueOf(index));
 		}
 	}
 
 	/**
 	 * Tuple for a function call whose target name is evaluated at runtime.
 	 */
 	public static final class IndirectCallTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final Map<String, IndirectFunctionTarget> userFunctions;
 		private final Map<String, ExtensionFunction> extensionFunctions;
 		private final long numActualParams;
 		private final String sourceName;
 		private final int sourceLine;
 
 		IndirectCallTuple(
 				Map<String, IndirectFunctionTarget> userFunctionsParam,
 				Map<String, ExtensionFunction> extensionFunctionsParam,
 				long numActualParamsParam,
 				String sourceNameParam,
 				int sourceLineParam) {
 			super(Opcode.INDIRECT_CALL);
 			userFunctions = userFunctionsParam;
 			extensionFunctions = extensionFunctionsParam;
 			numActualParams = numActualParamsParam;
 			sourceName = sourceNameParam;
 			sourceLine = sourceLineParam;
 		}
 
 		@Override
 		public void touch(List<Tuple> queue) {
 			for (IndirectFunctionTarget target : userFunctions.values()) {
 				target.resolve();
 			}
 			super.touch(queue);
 		}
 
 		@Override
 		public List<Address> getAddresses() {
 			List<Address> addresses = new ArrayList<Address>(userFunctions.size());
 			for (IndirectFunctionTarget target : userFunctions.values()) {
 				addresses.add(target.getAddress());
 			}
 			return addresses;
 		}
 
 		/**
 		 * Returns the user-defined functions available to the call site.
 		 *
 		 * @return function target map
 		 */
 		@SuppressFBWarnings(value = "EI_EXPOSE_REP", justification = "The map is an immutable metadata snapshot shared by every indirect call tuple")
 		public Map<String, IndirectFunctionTarget> getUserFunctions() {
 			return userFunctions;
 		}
 
 		/**
 		 * Returns the extension functions available to the call site.
 		 *
 		 * @return extension function map
 		 */
 		@SuppressFBWarnings(value = "EI_EXPOSE_REP", justification = "The map is an immutable metadata snapshot shared by every indirect call tuple")
 		public Map<String, ExtensionFunction> getExtensionFunctions() {
 			return extensionFunctions;
 		}
 
 		/**
 		 * Returns the number of actual parameters evaluated by the call site.
 		 *
 		 * @return actual parameter count
 		 */
 		public long getNumActualParams() {
 			return numActualParams;
 		}
 
 		/**
 		 * Returns the source name for runtime diagnostics.
 		 *
 		 * @return source name
 		 */
 		public String getSourceName() {
 			return sourceName;
 		}
 
 		/**
 		 * Returns the source line for runtime diagnostics.
 		 *
 		 * @return source line
 		 */
 		public int getSourceLine() {
 			return sourceLine;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + ", " + numActualParams;
 		}
 	}
 
 	/**
 	 * Tuple for extension function invocations.
 	 */
 	public static final class ExtensionTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final ExtensionFunction function;
 		private final long argCount;
 		private final boolean initial;
 
 		ExtensionTuple(ExtensionFunction function, long argCount, boolean initial) {
 			super(Opcode.EXTENSION);
 			this.function = function;
 			this.argCount = argCount;
 			this.initial = initial;
 		}
 
 		/**
 		 * Returns the extension function metadata.
 		 *
 		 * @return extension function
 		 */
 		public ExtensionFunction getFunction() {
 			return function;
 		}
 
 		/**
 		 * Returns the number of extension arguments.
 		 *
 		 * @return argument count
 		 */
 		public long getArgCount() {
 			return argCount;
 		}
 
 		/**
 		 * Indicates whether this tuple starts an extension call sequence.
 		 *
 		 * @return {@code true} for the initial extension call tuple
 		 */
 		public boolean isInitial() {
 			return initial;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name()
 					+ ", "
 					+ function.getKeyword()
 					+ ", "
 					+ argCount
 					+ ", "
 					+ initial;
 		}
 	}
 
 	/**
 	 * Tuple carrying a diagnostic message that the interpreter prints to the
 	 * warning stream when executed. The parser plants these before the
 	 * instruction they describe, so warnings appear in runtime order, exactly
 	 * where gawk would emit them.
 	 */
 	public static final class WarningTuple extends Tuple {
 		private static final long serialVersionUID = 1L;
 		private final String message;
 
 		WarningTuple(String message) {
 			super(Opcode.WARNING);
 			this.message = message;
 		}
 
 		/**
 		 * Returns the warning message to print.
 		 *
 		 * @return warning text
 		 */
 		public String getMessage() {
 			return message;
 		}
 
 		@Override
 		public String toString() {
 			return getOpcode().name() + stringArgument(message);
 		}
 	}
 }