java.lang.Object
- com.blackrook.expression.struct.Lexer

```
public class Lexer
extends Object
```
Breaks up a stream of characters into lexicographical tokens. Spaces, newlines, tabs, comments, and breaks in the stream are added if desired, otherwise, they are stripped out.
String delimiter characters take precedence over regular delimiters. Raw String delimiter characters take precedence over regular string delimiters. Delimiter characters take parsing priority over other characters. Delimiter evaluation priority goes: Comment Delimiter, Delimiter. Identifier evaluation priority goes: Keyword, CaseInsensitiveKeyword, Identifier.
Other implementations of this class may manipulate the stack as well (such as ones that do in-language stream inclusion).
If the system property com.blackrook.expression.util.Lexer.debug is set to true, this does debugging output to System.out.
Lexer functions are NOT thread-safe.

Author:

Matthew Tropiano

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`Lexer.Kernel`	This is a info kernel that tells a `Lexer` how to interpret certain characters and identifiers.
`static class`	`Lexer.Parser`	Abstract parser class.
`static class`	`Lexer.ReaderStack`	This holds a series of `Reader` streams such that the stream on top is the current active stream.
`static class`	`Lexer.Token`	Lexer token object.

Field Summary

Fields
Modifier and Type	Field	Description
`static boolean`	`DEBUG`
`static char`	`END_OF_LEXER`	Lexer end-of-stream char.
`static char`	`END_OF_STREAM`	Lexer end-of-stream char.
`static char`	`NEWLINE`	Lexer newline char.

Constructor Summary

Constructors
Constructor	Description
`Lexer(Lexer.Kernel kernel, Reader in)`	Creates a new lexer around a reader.
`Lexer(Lexer.Kernel kernel, String in)`	Creates a new lexer around a String, that will be wrapped into a StringReader.
`Lexer(Lexer.Kernel kernel, String name, Reader in)`	Creates a new lexer around a reader.
`Lexer(Lexer.Kernel kernel, String name, String in)`	Creates a new lexer around a String, that will be wrapped into a StringReader.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`clearCurrentLexeme()`	Clears the current token lexeme buffer.
`protected String`	`getCurrentLexeme()`	Gets the current token lexeme.
`int`	`getCurrentLineNumber()`	Gets the lexer's current stream's line number.
`Lexer.ReaderStack.Stream`	`getCurrentStream()`	Gets the current stream.
`String`	`getCurrentStreamName()`
`protected char`	`getRawStringEnd(char c)`	Gets the character that ends a raw String, using the starting character.
`protected int`	`getState()`
`protected char`	`getStringEnd(char c)`	Gets the character that ends a String, using the starting character.
`protected boolean`	`isCommentEndDelimiterStart(char c)`	Checks if this is a (or the start of a) block-comment-ending delimiter character.
`protected boolean`	`isDelimiterStart(char c)`	Checks if this is a (or the start of a) delimiter character.
`protected boolean`	`isDigit(char c)`	Convenience method for `Character.isDigit(char)`.
`protected boolean`	`isExponent(char c)`	Checks if char is the exponent character in a number.
`protected boolean`	`isExponentSign(char c)`	Checks if char is the exponent sign character in a number.
`protected boolean`	`isHexDigit(char c)`	Returns true if this is a hex digit (0-9, A-F, a-f).
`protected boolean`	`isLetter(char c)`	Convenience method for `Character.isLetter(char)`.
`protected boolean`	`isLexerEnd(char c)`	Checks if a char equals `END_OF_LEXER`.
`protected boolean`	`isNewline(char c)`	Checks if a char equals `NEWLINE`.
`protected boolean`	`isPoint(char c)`	Checks if a character is a decimal point (depends on locale/kernel).
`protected boolean`	`isRawStringStart(char c)`	Checks if this is a character that starts a multiline String.
`protected boolean`	`isSpace(char c)`	Checks if a char is a space.
`protected boolean`	`isStreamEnd(char c)`	Checks if a char equals `END_OF_STREAM`.
`protected boolean`	`isStringEnd(char c)`	Checks if this is a character that ends a String.
`protected boolean`	`isStringEscape(char c)`	Checks if this is a character that is a String escape character.
`protected boolean`	`isStringStart(char c)`	Checks if this is a character that starts a String.
`protected boolean`	`isTab(char c)`	Checks if a char is a tab.
`protected boolean`	`isUnderscore(char c)`	Convenience method for `c == '_'`.
`protected boolean`	`isWhitespace(char c)`	Convenience method for `Character.isWhitespace(char)`.
`protected boolean`	`modifyType(Lexer.Token token)`	Called when the lexer wants to create a token, but the lexeme of the token may cause this token to be a different type.
`Lexer.Token`	`nextToken()`	Gets the next token.
`void`	`pushStream(String name, Reader in)`	Pushes a stream onto the encapsulated reader stack.
`protected char`	`readChar()`	Reads a character from the stream.
`protected void`	`saveChar(char c)`	Saves a character for the next token.
`protected void`	`setDelimBreak(char delimChar)`	Sets if we are in a delimiter break.
`protected void`	`setMultilineStringStartAndEnd(char c)`	Sets the end character for a string.
`protected void`	`setState(int state)`	Sets the current state.
`protected void`	`setStringStartAndEnd(char c)`	Sets the end character for a string.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - DEBUG
```
public static boolean DEBUG
```
  - END_OF_LEXER
```
public static final char END_OF_LEXER
```
    Lexer end-of-stream char.
    
    See Also:
    
    Constant Field Values
  - END_OF_STREAM
```
public static final char END_OF_STREAM
```
    Lexer end-of-stream char.
    
    See Also:
    
    Constant Field Values
  - NEWLINE
```
public static final char NEWLINE
```
    Lexer newline char.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - Lexer
```
public Lexer(Lexer.Kernel kernel,
             String in)
```
    Creates a new lexer around a String, that will be wrapped into a StringReader. This will also assign this lexer a default name.
    
    Parameters:
    
    kernel - the lexer kernel to use for defining how to parse the input text.
    
    in - the string to read from.
  - Lexer
```
public Lexer(Lexer.Kernel kernel,
             String name,
             String in)
```
    Creates a new lexer around a String, that will be wrapped into a StringReader.
    
    Parameters:
    
    kernel - the lexer kernel to use for defining how to parse the input text.
    
    name - the name of this lexer.
    
    in - the reader to read from.
  - Lexer
```
public Lexer(Lexer.Kernel kernel,
             Reader in)
```
    Creates a new lexer around a reader. This will also assign this lexer a default name.
    
    Parameters:
    
    kernel - the kernel to use for this lexer.
    
    in - the reader to read from.
  - Lexer
```
public Lexer(Lexer.Kernel kernel,
             String name,
             Reader in)
```
    Creates a new lexer around a reader.
    
    Parameters:
    
    kernel - the kernel to use for this lexer.
    
    name - the name of this lexer.
    
    in - the reader to read from.
- Method Detail
  - getCurrentStreamName
```
public String getCurrentStreamName()
```
    Returns:
    
    the lexer's current stream name.
  - getCurrentLineNumber
```
public int getCurrentLineNumber()
```
    Gets the lexer's current stream's line number.
    
    Returns:
    
    the lexer's current stream's line number, or -1 if at Lexer end.
  - getCurrentStream
```
public Lexer.ReaderStack.Stream getCurrentStream()
```
    Gets the current stream.
    
    Returns:
    
    the name of the current stream.
  - pushStream
```
public void pushStream(String name,
                       Reader in)
```
    Pushes a stream onto the encapsulated reader stack.
    
    Parameters:
    
    name - the name of the stream.
    
    in - the reader reader.
  - nextToken
```
public Lexer.Token nextToken()
                      throws IOException
```
    Gets the next token. If there are no tokens left to read, this will return null. This method is NOT thread-safe!
    
    Returns:
    
    the next token, or null if no more tokens to read.
    
    Throws:
    
    IOException - if a token cannot be read by the underlying Reader.
  - modifyType
```
protected boolean modifyType(Lexer.Token token)
```
    Called when the lexer wants to create a token, but the lexeme of the token may cause this token to be a different type.
    By default, this handles space, tab, newline, delimiter, and identifier.
    If this method is overridden, this should have
    if (super.modifyType(token)) return true;
    right at the beginning.
    Parameters:
    
    token - the original token.
    
    Returns:
    
    true if the token's contents were changed, false if not.
  - readChar
```
protected char readChar()
                 throws IOException
```
    Reads a character from the stream.
    
    Returns:
    
    the character read, or END_OF_LEXER if no more characters, or END_OF_STREAM if end of current stream.
    
    Throws:
    
    IOException - if a character cannot be read.
  - getState
```
protected int getState()
```
    Returns:
    
    the current state.
  - setState
```
protected void setState(int state)
```
    Sets the current state.
    
    Parameters:
    
    state - the new state.
  - setDelimBreak
```
protected void setDelimBreak(char delimChar)
```
    Sets if we are in a delimiter break.
    
    Parameters:
    
    delimChar - the delimiter character that starts the break.
  - saveChar
```
protected void saveChar(char c)
```
    Saves a character for the next token.
    
    Parameters:
    
    c - the character to save into the current token.
  - setStringStartAndEnd
```
protected void setStringStartAndEnd(char c)
```
    Sets the end character for a string.
    
    Parameters:
    
    c - the character to set.
  - setMultilineStringStartAndEnd
```
protected void setMultilineStringStartAndEnd(char c)
```
    Sets the end character for a string.
    
    Parameters:
    
    c - the character to set.
  - getCurrentLexeme
```
protected String getCurrentLexeme()
```
    Gets the current token lexeme.
    
    Returns:
    
    the current contents of the token lexeme builder buffer.
  - clearCurrentLexeme
```
protected void clearCurrentLexeme()
```
    Clears the current token lexeme buffer.
  - isUnderscore
```
protected boolean isUnderscore(char c)
```
    Convenience method for c == '_'.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isLetter
```
protected boolean isLetter(char c)
```
    Convenience method for Character.isLetter(char).
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isDigit
```
protected boolean isDigit(char c)
```
    Convenience method for Character.isDigit(char).
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isHexDigit
```
protected boolean isHexDigit(char c)
```
    Returns true if this is a hex digit (0-9, A-F, a-f).
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isWhitespace
```
protected boolean isWhitespace(char c)
```
    Convenience method for Character.isWhitespace(char).
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isPoint
```
protected boolean isPoint(char c)
```
    Checks if a character is a decimal point (depends on locale/kernel).
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isExponent
```
protected boolean isExponent(char c)
```
    Checks if char is the exponent character in a number.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isExponentSign
```
protected boolean isExponentSign(char c)
```
    Checks if char is the exponent sign character in a number.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isSpace
```
protected boolean isSpace(char c)
```
    Checks if a char is a space.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isTab
```
protected boolean isTab(char c)
```
    Checks if a char is a tab.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isStringEscape
```
protected boolean isStringEscape(char c)
```
    Checks if this is a character that is a String escape character.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isStringStart
```
protected boolean isStringStart(char c)
```
    Checks if this is a character that starts a String.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isRawStringStart
```
protected boolean isRawStringStart(char c)
```
    Checks if this is a character that starts a multiline String.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - isStringEnd
```
protected boolean isStringEnd(char c)
```
    Checks if this is a character that ends a String.
    
    Parameters:
    
    c - the character to test.
    
    Returns:
    
    true if so, false if not.
  - getStringEnd
```
protected char getStringEnd(char c)
```
    Gets the character that ends a String, using the starting character.
    
    Parameters:
    
    c - the starting character.
    
    Returns:
    
    the corresponding end character, or the null character ('\0') if this does not end a string.
  - getRawStringEnd
```
protected char getRawStringEnd(char c)
```
    Gets the character that ends a raw String, using the starting character.
    
    Parameters:
    
    c - the starting character.
    
    Returns:
    
    the corresponding end character, or the null character ('\0') if this does not end a multi-line string.
  - isDelimiterStart
```
protected boolean isDelimiterStart(char c)
```
    Checks if this is a (or the start of a) delimiter character.
    
    Parameters:
    
    c - the character input.
    
    Returns:
    
    true if so, false if not.
  - isCommentEndDelimiterStart
```
protected boolean isCommentEndDelimiterStart(char c)
```
    Checks if this is a (or the start of a) block-comment-ending delimiter character.
    
    Parameters:
    
    c - the character input.
    
    Returns:
    
    true if so, false if not.
  - isStreamEnd
```
protected boolean isStreamEnd(char c)
```
    Checks if a char equals END_OF_STREAM.
    
    Parameters:
    
    c - the character input.
    
    Returns:
    
    true if so, false if not.
  - isLexerEnd
```
protected boolean isLexerEnd(char c)
```
    Checks if a char equals END_OF_LEXER.
    
    Parameters:
    
    c - the character input.
    
    Returns:
    
    true if so, false if not.
  - isNewline
```
protected boolean isNewline(char c)
```
    Checks if a char equals NEWLINE.
    
    Parameters:
    
    c - the character input.
    
    Returns:
    
    true if so, false if not.

Class Lexer

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DEBUG

END_OF_LEXER

END_OF_STREAM

NEWLINE

Constructor Detail

Lexer

Lexer

Lexer

Lexer

Method Detail

getCurrentStreamName

getCurrentLineNumber

getCurrentStream

pushStream

nextToken

modifyType

readChar

getState

setState

setDelimBreak

saveChar

setStringStartAndEnd

setMultilineStringStartAndEnd

getCurrentLexeme

clearCurrentLexeme

isUnderscore

isLetter

isDigit

isHexDigit

isWhitespace

isPoint

isExponent

isExponentSign

isSpace

isTab

isStringEscape

isStringStart

isRawStringStart

isStringEnd

getStringEnd

getRawStringEnd

isDelimiterStart

isCommentEndDelimiterStart

isStreamEnd

isLexerEnd

isNewline