production (Java CUP Parser Generator 0.9e API)

java.lang.Object
- java_cup.production

Direct Known Subclasses:

action_production
```
public class production
extends Object
```
This class represents a production in the grammar. It contains a LHS non terminal, and an array of RHS symbols. As various transformations are done on the RHS of the production, it may shrink. As a result a separate length is always maintained to indicate how much of the RHS array is still valid.
I addition to construction and manipulation operations, productions provide methods for factoring out actions (see remove_embedded_actions()), for computing the nullability of the production (i.e., can it derive the empty string, see check_nullable()), and operations for computing its first set (i.e., the set of terminals that could appear at the beginning of some string derived from the production, see check_first_set()).

Version:

last updated: 11/25/95

Author:

Scott Hudson

See Also:
production_part, symbol_part, action_part

Field Summary

Fields
Modifier and Type	Field and Description
`protected action_part`	`_action` An action_part containing code for the action to be performed when we reduce with this production.
`protected static Hashtable`	`_all` Table of all productions.
`protected terminal_set`	`_first_set` First set of the production.
`protected int`	`_index` Index number of the production.
`protected symbol_part`	`_lhs` The left hand side non-terminal.
`protected boolean`	`_nullable` Nullability of the production (can it derive the empty string).
`protected boolean`	`_nullable_known` Is the nullability of the production known or unknown?
`protected int`	`_num_reductions` Count of number of reductions using this production.
`protected production_part[]`	`_rhs` A collection of parts for the right hand side.
`protected int`	`_rhs_length` How much of the right hand side array we are presently using.
`protected static int`	`next_index` Static counter for assigning unique index numbers.

Constructor Summary

Constructors
Constructor and Description
`production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l)` Constructor with no action string.
`production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, String action_str)` Full constructor.

Method Summary

Methods
Modifier and Type	Method and Description
`protected String`	`action_translate(String act_string, int act_pos, Hashtable label_map, Hashtable label_types)` Translate all the label names within an action string to appropriate code.
`action_part`	`action()` An action_part containing code for the action to be performed when we reduce with this production.
`static Enumeration`	`all()` Access to all productions.
`terminal_set`	`check_first_set()` Update (and return) the first set based on current NT firsts.
`boolean`	`check_nullable()` Check to see if the production (now) appears to be nullable.
`boolean`	`equals(Object other)` Generic equality comparison.
`boolean`	`equals(production other)` Equality comparison.
`terminal_set`	`first_set()` First set of the production.
`int`	`hashCode()` Produce a hash code.
`int`	`index()` Index number of the production.
`protected static boolean`	`is_id_char(char c)` Determine if a character can be in a label id.
`protected static boolean`	`is_id_start(char c)` Determine if a given character can be a label id starter.
`protected String`	`label_translate(String id_str, int act_pos, Hashtable label_map, Hashtable label_types)` Determine the translation for one label id found within a code_string.
`symbol_part`	`lhs()` The left hand side non-terminal.
`protected int`	`merge_adjacent_actions(production_part[] rhs_parts, int len)` Helper routine to merge adjacent actions in a set of RHS parts
`void`	`note_reduction_use()` Increment the count of reductions with this non-terminal
`boolean`	`nullable_known()` Is the nullability of the production known or unknown?
`boolean`	`nullable()` Nullability of the production (can it derive the empty string).
`int`	`num_reductions()` Count of number of reductions using this production.
`static int`	`number()` Total number of productions.
`protected void`	`remove_embedded_actions()` Remove all embedded actions from a production by factoring them out into individual action production using new non terminals.
`int`	`rhs_length()` How much of the right hand side array we are presently using.
`production_part`	`rhs(int indx)` Access to the collection of parts for the right hand side.
`protected action_part`	`strip_trailing_action(production_part[] rhs_parts, int len)` Helper routine to strip a trailing action off rhs and return it
`String`	`to_simple_string()` Convert to a simpler string.
`String`	`toString()` Convert to a string.
`protected String`	`translate_labels(production_part[] rhs, int rhs_len, String final_action, String lhs_type)` Translate label names to appropriate code within all action strings.

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

- Field Detail
  - _all
```
protected static Hashtable _all
```
    Table of all productions. Elements are stored using their index as the key.
  - next_index
```
protected static int next_index
```
    Static counter for assigning unique index numbers.
  - _lhs
```
protected symbol_part _lhs
```
    The left hand side non-terminal.
  - _rhs
```
protected production_part[] _rhs
```
    A collection of parts for the right hand side.
  - _rhs_length
```
protected int _rhs_length
```
    How much of the right hand side array we are presently using.
  - _action
```
protected action_part _action
```
    An action_part containing code for the action to be performed when we reduce with this production.
  - _index
```
protected int _index
```
    Index number of the production.
  - _num_reductions
```
protected int _num_reductions
```
    Count of number of reductions using this production.
  - _nullable_known
```
protected boolean _nullable_known
```
    Is the nullability of the production known or unknown?
  - _nullable
```
protected boolean _nullable
```
    Nullability of the production (can it derive the empty string).
  - _first_set
```
protected terminal_set _first_set
```
    First set of the production. This is the set of terminals that could appear at the front of some string derived from this production.
- Constructor Detail
  - production
```
public production(non_terminal lhs_sym,
          production_part[] rhs_parts,
          int rhs_l,
          String action_str)
           throws internal_error
```
    Full constructor. This constructor accepts a LHS non terminal, an array of RHS parts (including terminals, non terminals, and actions), and a string for a final reduce action. It does several manipulations in the process of creating a production object. After some validity checking it translates labels that appear in actions into code for accessing objects on the runtime parse stack. It them merges adjacent actions if they appear and moves any trailing action into the final reduce actions string. Next it removes any embedded actions by factoring them out with new action productions. Finally it assigns a unique index to the production.
    Factoring out of actions is accomplished by creating new "hidden" non terminals. For example if the production was originally:
```
    A ::= B {action} C D
  
```
    then it is factored into two productions:
```
    A ::= B X C D
    X ::= {action}
  
```
    (where X is a unique new non terminal). This has the effect of placing all actions at the end where they can be handled as part of a reduce by the parser.
    Throws:
    
    internal_error
  - production
```
public production(non_terminal lhs_sym,
          production_part[] rhs_parts,
          int rhs_l)
           throws internal_error
```
    Constructor with no action string.
    
    Throws:
    
    internal_error
- Method Detail
  - all
```
public static Enumeration all()
```
    Access to all productions.
  - number
```
public static int number()
```
    Total number of productions.
  - lhs
```
public symbol_part lhs()
```
    The left hand side non-terminal.
  - rhs
```
public production_part rhs(int indx)
                    throws internal_error
```
    Access to the collection of parts for the right hand side.
    
    Throws:
    
    internal_error
  - rhs_length
```
public int rhs_length()
```
    How much of the right hand side array we are presently using.
  - action
```
public action_part action()
```
    An action_part containing code for the action to be performed when we reduce with this production.
  - index
```
public int index()
```
    Index number of the production.
  - num_reductions
```
public int num_reductions()
```
    Count of number of reductions using this production.
  - note_reduction_use
```
public void note_reduction_use()
```
    Increment the count of reductions with this non-terminal
  - nullable_known
```
public boolean nullable_known()
```
    Is the nullability of the production known or unknown?
  - nullable
```
public boolean nullable()
```
    Nullability of the production (can it derive the empty string).
  - first_set
```
public terminal_set first_set()
```
    First set of the production. This is the set of terminals that could appear at the front of some string derived from this production.
  - is_id_start
```
protected static boolean is_id_start(char c)
```
    Determine if a given character can be a label id starter.
    
    Parameters:
    c - the character in question.
  - is_id_char
```
protected static boolean is_id_char(char c)
```
    Determine if a character can be in a label id.
    
    Parameters:
    c - the character in question.
  - label_translate
```
protected String label_translate(String id_str,
                     int act_pos,
                     Hashtable label_map,
                     Hashtable label_types)
```
    Determine the translation for one label id found within a code_string. Symbols appearing in the RHS correspond to objects found on the parse stack at runtime. The code to access them, becomes code to access an object at the appropriate offset from the top of the stack, and then cast that to the proper type.
    
    Parameters:
    id_str - the name of the id to be translated.
    act_pos - the original position of the action it appears in.
    label_map - a hash table mapping labels to positions in the RHS.
    type_map - a hash table mapping labels to declared symbol types.
  - action_translate
```
protected String action_translate(String act_string,
                      int act_pos,
                      Hashtable label_map,
                      Hashtable label_types)
```
    Translate all the label names within an action string to appropriate code.
    
    Parameters:
    act_string - the string to be translated
    act_pos - the position that the action originally held in the production.
    label_map - a hash table mapping labels to positions in the RHS.
    type_map - a hash table mapping labels to declared symbol types.
  - translate_labels
```
protected String translate_labels(production_part[] rhs,
                      int rhs_len,
                      String final_action,
                      String lhs_type)
```
    Translate label names to appropriate code within all action strings.
    
    Parameters:
    rhs - array of RHS parts.
    rhs_len - how much of rhs to consider valid.
    final_action - the final action string of the production.
    lhs_type - the object type associated with the LHS symbol.
  - merge_adjacent_actions
```
protected int merge_adjacent_actions(production_part[] rhs_parts,
                         int len)
```
    Helper routine to merge adjacent actions in a set of RHS parts
    
    Parameters:
    rhs_parts - array of RHS parts.
    len - amount of that array that is valid.
    
    Returns:
    remaining valid length.
  - strip_trailing_action
```
protected action_part strip_trailing_action(production_part[] rhs_parts,
                                int len)
```
    Helper routine to strip a trailing action off rhs and return it
    
    Parameters:
    rhs_parts - array of RHS parts.
    len - how many of those are valid.
    
    Returns:
    the removed action part.
  - remove_embedded_actions
```
protected void remove_embedded_actions()
                                throws internal_error
```
    Remove all embedded actions from a production by factoring them out into individual action production using new non terminals. if the original production was:
```
    A ::= B {action1} C {action2} D 
  
```
    then it will be factored into:
```
    A ::= B NT$1 C NT$2 D
    NT$1 ::= {action1}
    NT$2 ::= {action2}
  
```
    where NT$1 and NT$2 are new system created non terminals.
    Throws:
    
    internal_error
  - check_nullable
```
public boolean check_nullable()
                       throws internal_error
```
    Check to see if the production (now) appears to be nullable. A production is nullable if its RHS could derive the empty string. This results when the RHS is empty or contains only non terminals which themselves are nullable.
    
    Throws:
    
    internal_error
  - check_first_set
```
public terminal_set check_first_set()
                             throws internal_error
```
    Update (and return) the first set based on current NT firsts. This assumes that nullability has already been computed for all non terminals and productions.
    
    Throws:
    
    internal_error
  - equals
```
public boolean equals(production other)
```
    Equality comparison.
  - equals
```
public boolean equals(Object other)
```
    Generic equality comparison.
    
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Produce a hash code.
    
    Overrides:
    
    hashCode in class Object
  - toString
```
public String toString()
```
    Convert to a string.
    
    Overrides:
    
    toString in class Object
  - to_simple_string
```
public String to_simple_string()
                        throws internal_error
```
    Convert to a simpler string.
    
    Throws:
    
    internal_error

Class production

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

_all

next_index

_lhs

_rhs

_rhs_length

_action

_index

_num_reductions

_nullable_known

_nullable

_first_set

Constructor Detail

production

production

Method Detail

all

number

lhs

rhs

rhs_length

action

index

num_reductions

note_reduction_use

nullable_known

nullable

first_set

is_id_start

is_id_char

label_translate

action_translate

translate_labels

merge_adjacent_actions

strip_trailing_action

remove_embedded_actions

check_nullable

check_first_set

equals

equals

hashCode

toString

to_simple_string