C# Group.GetRange方法代码示例

        /// <summary>
        /// Parses an if statement.
        /// </summary>
        /// <param name="group">The group to parse.</param>
        /// <returns>
        /// If a statement or block of code is executed, then the result of that code is returned, otherwise the
        /// boolean result of the logical expression is returned. A TException is returned when there is an error.
        /// </returns>
        TType ParseIfGroup(Group group)
        {
            /* BNF for if statement:
             *      <if-statement> ::= 'if' <condition> ',' ( <statements> | <block-no-end> 'else' <statements> )
             *      <block-no-end> ::= <new-line> (<statement> <new-line>)*
             * The 'if' is assumed to have already been checked for
             */
            if (group.Count < 2)
                return new TException(this, "Statement could not be evaluated",
                    "if statement must be given a condition");

            int commaIndex = group.IndexOf(",");
            if (commaIndex < 0)
                return new TException(this, "if statment invalid", "comma required after condition");

            Group conditionGroup = new Group(null);
            conditionGroup.AddRange(group.GetRange(1, commaIndex - 1));
            TType value = ParseGroup(conditionGroup);
            if (value is TException) return value;

            TBoolean result = value as TBoolean;
            if (result == null)
            {
                bool success = false;
                TVariable variable = value as TVariable;
                if (variable != null)
                {
                    result = variable.Value as TBoolean;
                    if (result != null) success = true;
                }
                if (!success)
                    return new TException(this, "Condition does not evaluate to a boolean value", "yes or no");
            }

            if (group.Count > commaIndex + 1) // If there is no block after the 'if' <condition> ','
            {
                // If there is an else and it's at the end of the line, get a block for the else
                int elseIndex = group.IndexOf("else", commaIndex + 1);
                TBlock elseBlock = null;
                if (elseIndex == group.Count - 1)
                {
                    TException exception;
                    elseBlock = new TBlock(this, out exception, false);
                    if (exception != null) return exception;
                }

                if (result.Value)
                {
                    // Execute the code between the comma and the end of the statement or the else (if any).
                    // If there isn't anything to execute, then a block is created (near the end of this method)
                    Group statementGroup = new Group(null);
                    if (elseIndex < 0)
                        statementGroup.AddRange(group.GetRange(commaIndex + 1, group.Count - (commaIndex + 1)));
                    else
                        statementGroup.AddRange(group.GetRange(commaIndex + 1, elseIndex - (commaIndex + 1)));

                    if (statementGroup.Count > 0) return ParseGroup(statementGroup);
                }
                else if (elseIndex >= 0)
                {
                    if (elseBlock == null)
                    {
                        Group statementGroup = new Group(null);
                        statementGroup.AddRange(group.GetRange(elseIndex + 1, group.Count - (elseIndex + 1)));
                        if (statementGroup.Count > 0) return ParseGroup(statementGroup);
                    }
                    else
                    {
                        bool exitFromFunction, breakUsed;
                        return elseBlock.Execute(this, out exitFromFunction, out breakUsed);
                    }
                }
                else return result;
            }

            { // This code is executed if there is a block after the 'if' <condition> ',' instead of a single statement
                TException exception;
                TBlock block = new TBlock(this, out exception, true);
                if (exception != null) return exception;

                bool exitFromFunction, breakUsed;
                if (result.Value) return block.Execute(this, out exitFromFunction, out breakUsed, true);
                if (block.HasElse()) return block.Execute(this, out exitFromFunction, out breakUsed, false);
            }

            return result;
        }

        /// <summary>
        /// Parses an assignment operation.
        /// </summary>
        /// <param name="group">The group to parse.</param>
        /// <returns>The assigned variable or function on success, otherwise a TException.</returns>
        TType ParseAssignmentGroup(Group group)
        {
            /* BNF for assignment:
             *      <assignment>       ::= 'let' ( <variable-assignment> | <function-declaration> )
             *      <var-assignment>   ::= <identifier> '=' <expression>
             *      <func-declaration> ::= <identifier> '(' { <parameters> } ')' '=' <statements>
             *      <parameters>       ::= <identifier> { ',' <identifier> }*
             *      <statements>       ::= <block> | <statement>
             *      <block>            ::= <new-line> (<statement> <new-line>)* 'end'
             * You can probably guess what <identifier>, <statement> and <new-line> are
             * The 'let' is assumed to have already been checked for
             */
            int equalsIndex = group.IndexOf("=");
            if (equalsIndex < 0) return new TException(this, "Variable or function could not be assigned a value");

            // Could be assigning a dereferenced variable
            TException exception = ParseReferencesOfGroup(group, equalsIndex);
            if (exception != null) return exception;

            if (group.Count == 1) return new TException(this, "Could not assign variable", "no variable name given");

            string variableName = group[1] as string;
            TVariable existingVariable = null;

            if (variableName == null)
            {
                exception = new TException(this, "Could not assign variable", "invalid variable name given");

                // Check if an existing variable or function is being assigned
                Group groupToParse = group[1] as Group;
                TType value = group[1] as TType;
                if (groupToParse != null) value = ParseGroup(groupToParse);
                if (value == null) return exception;

                TVariable variable = value as TVariable;
                if (variable != null) existingVariable = variable;
                else
                {
                    TFunction function = value as TFunction;
                    if (function != null) variableName = function.Name;
                    else return exception;
                }
            }

            if (group.Count == 2) return new TException(this, "Variable could not be assigned a value");
            string assignmentOperator = group[2] as string;
            if (assignmentOperator == null) // Now we assume that we're dealing with a function declaration
            {
                Group paramGroup = group[2] as Group;
                if (paramGroup == null) // The user probably just wanted to assign a variable but made a typo
                    return new TException(this, "Variable could not be assigned a value",
                        "value to assign to variable must be given");

                // Get the identifiers of all the parameters within the brackets, keeping strict watch on comma usage
                TParameterList paramList = new TParameterList();
                bool commaExpected = false;
                for (int i = 0; i < paramGroup.Count; ++i)
                {
                    if (commaExpected && (i == paramGroup.Count - 1))
                        return new TException(this, "Parameters could not be parsed", "last parameter missing");

                    string paramName = paramGroup[i] as string;

                    if (commaExpected && (paramName != ",")) paramName = null;

                    if (paramName == null) return new TException(this, "Parameters could not be parsed",
                        "invalid parameter name given");

                    if (!commaExpected) paramList.Add(paramName);
                    commaExpected = !commaExpected;
                }

                exception = new TException(this, "Function could not be given a body", "function body must be given");
                if (group.Count == 3) return exception;
                assignmentOperator = group[3] as string;
                if (assignmentOperator == null) return exception;
                else if (assignmentOperator != "=") return exception;

                TFunction function;
                if (group.Count == 4) // statement is just 'let <i><params> =', so get a block
                {
                    TBlock block = new TBlock(this, out exception, false);
                    if (exception != null) return exception;
                    function = new TFunction(variableName ?? existingVariable.Identifier, block,
                        paramList.ParameterNames, null);
                }
                else // Create a single line function
                {
                    Group funcBody = new Group(null);
                    funcBody.AddRange(group.GetRange(4, group.Count - 4));
                    function = new TFunction(variableName ?? existingVariable.Identifier, funcBody.ToString(),
                        paramList.ParameterNames, null);
                }

                exception = TFunction.AddFunction(this, function);
//.........这里部分代码省略.........

        /// <summary>
        /// Parses and puts into effect an interpreter directive.
        /// </summary>
        /// <param name="group">The group containing the directive.</param>
        /// <returns>TNil on success, otherwise a TException.</returns>
        TType ParseDirectiveGroup(Group group)
        {
            if (group.Count < 2) return new TException(this, "No directive given");

            string directive = group[1] as string;
            if (directive == null) return new TException(this, "No directive given");

            switch (directive)
            {
                case "STRICT": // Toggles strict mode. Usage: '#STRICT yes', '#STRICT no' or '#STRICT <condition>'
                    if (group.Count > 2)
                    {
                        Group conditionGroup = new Group(null);
                        conditionGroup.AddRange(group.GetRange(2, group.Count - 2));
                        TType value = ParseGroup(conditionGroup);
                        if (value is TException) return value;

                        TBoolean result = value as TBoolean;
                        if (result == null) return new TException(this, "Directive 'STRICT' could not be used",
                            "invalid argument; use yes, no or a condition");

                        Strict = result.Value;
                        if (Strict) System.Console.WriteLine("Interpreter running in strict mode");
                        else System.Console.WriteLine("Interpreter not running in strict mode");

                        return TNil.Instance;
                    }
                    else return new TException(this, "Directive 'STRICT' could not be used",
                        "invalid argument (none given); use yes, no or a condition");
            }

            return new TException(this, "Could not use directive", "directive '" + directive + "' not recognised");
        }

        /// <summary>
        /// Parses a while loop statement.
        /// </summary>
        /// <param name="group">The group to parse.</param>
        /// <returns>TNil on success, otherwise a TException.</returns>
        TType ParseWhileGroup(Group group)
        {
            /* BNF for while loop:
             *      <while-loop> ::= 'while' <condition> ',' ( <statement> | <block> )
             * The 'while' is assumed to have already been checked for
             */
            if (group.Count == 1) return new TException(this, "Statement could not be evaluated",
                "while loop must be given a condition");

            int commaIndex = group.IndexOf(",");
            if (commaIndex < 0) return new TException(this, "while loop invalid", "comma required after condition");

            if (group.Count == 1)
                return new TException(this,
                    "Statement could not be evaluated", "while loop must be given a condition");

            Group conditionGroup = new Group(null);
            conditionGroup.AddRange(group.GetRange(1, commaIndex - 1));

            Group statementGroup = null;
            TBlock block = null;
            if (group.Count > commaIndex + 1) // If there is a statement after the comma, use that statement
            {
                statementGroup = new Group(null);
                statementGroup.AddRange(group.GetRange(commaIndex + 1, group.Count - (commaIndex + 1)));
            }
            else // Otherwise get a block
            {
                TException exception;
                block = new TBlock(this, out exception, false);
                if (exception != null) return exception;
            }

            TType returnValue = TNil.Instance;
            while (true)
            {
                // Parse the condition, and if it's true run the block or single statement, otherwise return MNil
                TType value = ParseGroup((Group)conditionGroup.Clone());
                if (value is TException) return value;

                TBoolean result = value as TBoolean;
                if (result == null)
                {
                    bool success = false;
                    TVariable variable = value as TVariable;
                    if (variable != null)
                    {
                        result = variable.Value as TBoolean;
                        if (result != null) success = true;
                    }
                    if (!success)
                        return new TException(this, "Condition does not evaluate to a boolean value", "yes or no");
                }

                if (result.Value)
                {
                    bool breakUsed = false;
                    if (statementGroup != null) returnValue = ParseGroup((Group)statementGroup.Clone());
                    else
                    {
                        bool exitFromFunction;
                        returnValue = block.Execute(this, out exitFromFunction, out breakUsed);
                        if (exitFromFunction) return returnValue;
                    }
                    if ((returnValue is TException) || breakUsed) return returnValue;
                }
                else return returnValue;

                if (!alive) return TNil.Instance;
            }
        }