Package java_cup
Class production
- java.lang.Object
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- java_cup.production
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- Direct Known Subclasses:
action_production
public class production extends java.lang.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: 7/3/96
- Author:
- Frank Flannery
- See Also:
production_part
,symbol_part
,action_part
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Field Summary
Fields Modifier and Type Field Description protected action_part
_action
An action_part containing code for the action to be performed when we reduce with this production.protected static java.util.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_assoc
protected int
_rhs_length
How much of the right hand side array we are presently using.protected int
_rhs_prec
The precedence of the ruleprotected static int
next_index
Static counter for assigning unique index numbers.
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Constructor Summary
Constructors Constructor 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, int prec_num, int prec_side)
production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, java.lang.String action_str)
Full constructor.production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, java.lang.String action_str, int prec_num, int prec_side)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description action_part
action()
An action_part containing code for the action to be performed when we reduce with this production.static java.util.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.static void
clear()
protected java.lang.String
declare_labels(production_part[] rhs, int rhs_len, java.lang.String final_action)
Declare label names as valid variables within the action stringboolean
equals(production other)
Equality comparison.boolean
equals(java.lang.Object other)
Generic equality comparison.static production
find(int indx)
Lookup a production by index.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.symbol_part
lhs()
The left hand side non-terminal.protected java.lang.String
make_declaration(java.lang.String labelname, java.lang.String stack_type, int offset)
Return label declaration codeprotected int
merge_adjacent_actions(production_part[] rhs_parts, int len)
Helper routine to merge adjacent actions in a set of RHS partsvoid
note_reduction_use()
Increment the count of reductions with this non-terminalboolean
nullable()
Nullability of the production (can it derive the empty string).boolean
nullable_known()
Is the nullability of the production known or unknown?int
num_reductions()
Count of number of reductions using this production.static int
number()
Total number of productions.int
precedence_num()
Access to the precedence of the ruleint
precedence_side()
protected void
remove_embedded_actions()
Remove all embedded actions from a production by factoring them out into individual action production using new non terminals.production_part
rhs(int indx)
Access to the collection of parts for the right hand side.int
rhs_length()
How much of the right hand side array we are presently using.void
set_precedence_num(int prec_num)
Setting the precedence of a rulevoid
set_precedence_side(int prec_side)
protected action_part
strip_trailing_action(production_part[] rhs_parts, int len)
Helper routine to strip a trailing action off rhs and return itjava.lang.String
to_simple_string()
Convert to a simpler string.java.lang.String
toString()
Convert to a string.
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Field Detail
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_all
protected static java.util.Hashtable _all
Table of all productions. Elements are stored using their index as the key.
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next_index
protected static int next_index
Static counter for assigning unique index numbers.
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_lhs
protected symbol_part _lhs
The left hand side non-terminal.
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_rhs_prec
protected int _rhs_prec
The precedence of the rule
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_rhs_assoc
protected int _rhs_assoc
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_rhs
protected production_part[] _rhs
A collection of parts for the right hand side.
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_rhs_length
protected int _rhs_length
How much of the right hand side array we are presently using.
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_action
protected action_part _action
An action_part containing code for the action to be performed when we reduce with this production.
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_index
protected int _index
Index number of the production.
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_num_reductions
protected int _num_reductions
Count of number of reductions using this production.
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_nullable_known
protected boolean _nullable_known
Is the nullability of the production known or unknown?
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_nullable
protected boolean _nullable
Nullability of the production (can it derive the empty string).
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_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.
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Constructor Detail
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production
public production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, java.lang.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
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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
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production
public production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, java.lang.String action_str, int prec_num, int prec_side) throws internal_error
- Throws:
internal_error
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production
public production(non_terminal lhs_sym, production_part[] rhs_parts, int rhs_l, int prec_num, int prec_side) throws internal_error
- Throws:
internal_error
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Method Detail
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all
public static java.util.Enumeration all()
Access to all productions.
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find
public static production find(int indx)
Lookup a production by index.
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clear
public static void clear()
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number
public static int number()
Total number of productions.
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lhs
public symbol_part lhs()
The left hand side non-terminal.
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precedence_num
public int precedence_num()
Access to the precedence of the rule
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precedence_side
public int precedence_side()
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set_precedence_num
public void set_precedence_num(int prec_num)
Setting the precedence of a rule
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set_precedence_side
public void set_precedence_side(int prec_side)
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rhs
public production_part rhs(int indx) throws internal_error
Access to the collection of parts for the right hand side.- Throws:
internal_error
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rhs_length
public int rhs_length()
How much of the right hand side array we are presently using.
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action
public action_part action()
An action_part containing code for the action to be performed when we reduce with this production.
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index
public int index()
Index number of the production.
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num_reductions
public int num_reductions()
Count of number of reductions using this production.
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note_reduction_use
public void note_reduction_use()
Increment the count of reductions with this non-terminal
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nullable_known
public boolean nullable_known()
Is the nullability of the production known or unknown?
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nullable
public boolean nullable()
Nullability of the production (can it derive the empty string).
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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.
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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.
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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.
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make_declaration
protected java.lang.String make_declaration(java.lang.String labelname, java.lang.String stack_type, int offset)
Return label declaration code- Parameters:
labelname
- the label namestack_type
- the stack type of label?
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declare_labels
protected java.lang.String declare_labels(production_part[] rhs, int rhs_len, java.lang.String final_action)
Declare label names as valid variables within the action string- 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.
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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.
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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.
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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
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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
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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
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equals
public boolean equals(production other)
Equality comparison.
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equals
public boolean equals(java.lang.Object other)
Generic equality comparison.- Overrides:
equals
in classjava.lang.Object
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hashCode
public int hashCode()
Produce a hash code.- Overrides:
hashCode
in classjava.lang.Object
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toString
public java.lang.String toString()
Convert to a string.- Overrides:
toString
in classjava.lang.Object
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to_simple_string
public java.lang.String to_simple_string() throws internal_error
Convert to a simpler string.- Throws:
internal_error
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