Dot (Syntax Compiler-Compiler 4.2.0 API)

java.lang.Object
- me.jaimegarza.syntax.model.parser.Dot

```
public class Dot
extends Object
```
~pojo class

During the table creation process an algorithm is performed to obtain a state machine (turing machine) with the shifts and reduces needed at all states of the system. To do that, we analyze every possible state of the grammar by the using the concept of a dot.
The algorithm is as follows:
1. Locate the initial symbol, and place a dot at the first element of the rules where the initial symbol is on the left hand. For example:
```
  S -> . E
```
2. Compute the closure of a state on every non terminal symbol. The closure is the set of rules that have the non terminal in the left hand side, for each non terminal with a dot at its left. A dot is assigned at the first position on the closure rules. For example:
```
  S -> .E
  closure:
  E -> .E + T
  E -> .E - T
```
  Closure rules are identical when the two rules are the same, and the dot positions are also the same.
3. After the state (set of rules and dots) is known, it is checked for uniqueness.
4. We iterate through each of the states moving dots to the right of non terminals and terminals, and finding the destination state. For instance:
```
  state 0
  S -> .E
  closure:
  E -> .E + T   closure on E
  E -> .E - T   closure on E
  E -> .T       closure on E
  T -> .T * F   closure on T
  T -> .T / F   closure on T
  T -> .F       closure on T
  F -> .number  closure on F
  F -> .- F     closure on F
  F -> .( F )   closure on F
 
  state 1 (with its closure, transition of state 0 with E)
  S -> E .
  E -> E .+ T
  E -> E .- T
  
  state 2 (with its closure, transition of state 1 with +)
  E -> E + .T
  closure:
  T -> .T * F   closure on T
  T -> .T / F   closure on T
  T -> .F       closure on T
  F -> .number  closure on F
  F -> .- F     closure on F
  F -> .( F )   closure on F
  
  etc...
```
Out of this dot traversal, all states are known, and all its transition to other states are also known.
As such, a dot is a positional element that defines a rule, and the position the observed rule item.
Author:

jaimegarza@gmail.com

Constructor Summary

Constructors
Constructor and Description

Dot(State state, Rule rule, RuleItem item)
Construct a dot

Constructors
Constructor and Description
`Dot(State state, Rule rule, RuleItem item)` Construct a dot

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`addAllLookaheads(Set<Integer> symbolIds)` merge lookaheads into this dot
`void`	`addLookahead(int symbolId)` Adds a non terminal to the dot
`static boolean`	`equals(Dot a, Dot b)` Utility method to compare two dots, accounting for nulls
`boolean`	`equals(Object obj)`
`RuleItem`	`getItem()`
`Set<Integer>`	`getLookahead()`
`Rule`	`getRule()`
`State`	`getState()`
`Dot`	`next()` State dots are linked.
`RuleItem`	`nextItem()` Given a dot, move the dot to the right of the pointed symbol It does this by going to the rule and finding the rule item i+1 from the rule item i.
`void`	`setItem(RuleItem item)`
`void`	`setRule(Rule rule)`
`void`	`setState(State state)`
`String`	`toString()` Returns a "dotted" representation of the rule items in the rule

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

- Constructor Detail
  - Dot
```
public Dot(State state,
           Rule rule,
           RuleItem item)
```
    Construct a dot
    
    Parameters:
    
    state - is the vertical parent State of this dot
    
    rule - is the Rule where this dot points.
    
    item - is the RuleItem to the right of the dot. It can be null.
- Method Detail
  - nextItem
```
public RuleItem nextItem()
```
    Given a dot, move the dot to the right of the pointed symbol
    It does this by going to the rule and finding the rule item i+1 from the rule item i.
    
    Returns:
    
    the next rule item, or null
  - next
```
public Dot next()
```
    State dots are linked. Get the next dot in the state.
    
    Returns:
    
    the next dot, or null.
    
    See Also:
    
    for a "state view" of its dots.
  - addLookahead
```
public void addLookahead(int symbolId)
```
    Adds a non terminal to the dot
    
    Parameters:
    
    symbolId - is the id of the non terminal
  - addAllLookaheads
```
public void addAllLookaheads(Set<Integer> symbolIds)
```
    merge lookaheads into this dot
    
    Parameters:
    
    symbolIds - is the set of symbols that make up the lookahead
  - getLookahead
```
public Set<Integer> getLookahead()
```
    Returns:
    
    the lookahead
  - getState
```
public State getState()
```
    Returns:
    
    the state
  - setState
```
public void setState(State state)
```
    Parameters:
    
    state - the state to set
  - getItem
```
public RuleItem getItem()
```
    Returns:
    
    the item
  - setItem
```
public void setItem(RuleItem item)
```
    Parameters:
    
    item - the item to set
  - getRule
```
public Rule getRule()
```
    Returns:
    
    the rule
  - setRule
```
public void setRule(Rule rule)
```
    Parameters:
    
    rule - the rule to set
  - equals
```
public boolean equals(Object obj)
```
    Overrides:
    
    equals in class Object
    
    See Also:
    
    Object.equals(java.lang.Object)
  - equals
```
public static boolean equals(Dot a,
                             Dot b)
```
    Utility method to compare two dots, accounting for nulls
    
    Parameters:
    
    a - the first element. Can be null.
    
    b - the second element. Can be null.
    
    Returns:
    
    true if both are null, otherwise the result of a.equals(b)
  - toString
```
public String toString()
```
    Returns a "dotted" representation of the rule items in the rule
    
    Overrides:
    
    toString in class Object
    
    See Also:
    
    Object.toString()

Class Dot

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Dot

Method Detail

nextItem

next

addLookahead

addAllLookaheads

getLookahead

getState

setState

getItem

setItem

getRule

setRule

equals

equals

toString