JPH01187635A - Analysis system for reduction contention - Google Patents

Abstract

PURPOSE:To facilitate determinations of the cause of contention and resolution thereof in an SLR(1) syntactic analysis system by displaying detailed information related to reduction contention at the time when the reduction contention occurs. CONSTITUTION:A syntactic regulation analyzing part 1 to perform SLR(1) analysis according to an inputted syntactic regulation, a contention recognizing part 2 to recognize the state of the contention to occur in a case that the syntactic regulation is not SLR(1) grammar, and a reduction contention analyzing part 3 to analyze the reduction contention and display the example of syntactic structure in which the reduction contention occurs and its structure, are constituted. Then, when a non-terminal symbol and a terminal symbol in its follow set are given, a path from an ancestor common to the non-terminal symbol and the terminal symbol is retrieved on a syntactic tree, and as the result, in a case that the syntactic regulation is not the SLR(1) grammar, the example of the syntactic structure in which the reduction contention occurs is displayed. Thus, the determination of the cause of the contention or the analysis of the contention can be easily performed.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to BNF (Baek
(us -Nour form) Based on input syntax rules given in the form Among structural analysis methods, an analysis method called LIL syntax analysis is famous.LR syntax analysis is
First, the state in the middle of parsing the structure of a given input syntax rule is called the LR(0) term, and the LR parsing state, which is a set of L)L(01 terms, is divided into several core L-terms. (0)
This is a method of parsing by generating a table that is generated from a term and transitions to the next L-level parsing state depending on the next input symbol read when in a certain L-level parsing state. In this L parsing, the input syntax symbol read next causes the next transition to Ll (parsing state A state that does not overlap is an inconvenient state, and such an inconvenient state is a state where a conflict occurs. Follow (fol) is a set of symbols that can follow a certain symbol in a syntax rule.
1ow ) is a set of symbols that can be the beginning of a symbol string in a syntactic rule.
The syntax analysis method that uses the follow set to resolve the inconvenient state is SLR (1) syntax analysis, which is a method that is often used among the LR syntax analysis methods (compiler). Ikuo Nakata, Industrial Books 100
(pages 126 to 126), when a conflict occurs in such L8 syntax analysis, the analysis of the conflict state is to search for the L1%(0) term causing the conflict in the state where the conflict is occurring, and then It only displayed the syntax rules corresponding to the L(0) term and the input symbols in that case. For example, when a syntax rule such as that shown in FIG. 3 is input, an example of the display is shown in FIG. 6.

[Problem that the invention seeks to solve]

In the conflict analysis mentioned above, in the state where a conflict is occurring, search for the L (term 01) that is causing the conflict and calculate its LR
Since the syntax rule corresponding to the fO1 term and the input symbol in that case are only displayed, it is difficult to determine the cause of the conflict. An object of the present invention is to perform a conflict analysis that displays more detailed information during a conflict, which is called a reduction conflict.

[Means for solving problems]

In the reduced conflict analysis method of the present invention, syntax rules given in BNF format are input, and among the L8 syntax analysis methods based on the syntax rules, especially S1. R(1) In a data structure analysis method that performs syntactic analysis, non-terminal symbols and their follo
Given a terminal symbol included in the w collection, a path from the common ancestor of the non-terminal symbol and the terminal symbol is searched on the syntax tree, and as a result, the syntax rule is S L R (
1) Display examples of syntactic structures in which reduction conflicts occur when they are not grammars.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the reduction competition analysis method of the present invention. In FIG. 1, 1 is a syntax rule analysis unit that performs S L R (1) analysis as described in [Prior Art] based on an input syntax rule, and 2 is a syntax rule analysis unit that performs S L R (1) analysis based on an input syntax rule.
R(1) is a conflict recognition unit that recognizes the state of conflict that occurs when it is not a grammar, and 3 is a reduction conflict analysis unit that analyzes reduction conflicts and displays examples of syntactic structures in which reduction conflicts occur and their structures.

Figure 2 shows an example of a syntactic structure by searching for a path from the common ancestor of a non-terminal symbol and a terminal symbol on a syntax tree as a means of performing the reduced conflict analysis and display of reduced conflict information in Figure 1 and 3. This is a processing flow that displays the structure.

Figure 3 is an example of an input syntax rule that is not an SLR (1) grammar, Figure 4 +1), +2) is an example of a syntax tree that causes reduction conflicts in the syntax rules of Figure 3, and Figure 5 is Figure 6.2. This is an example of displaying the analysis information of the reduced state of the syntax rule "Nl:T4 T5°" in line 1.

First, the outline of the reduction competition analysis process of the present invention will be explained with reference to FIG. The input syntax rules are passed to the syntax rule analysis unit 1 and subjected to SLR(1) syntax analysis. If the syntax rule is not a 5L)L(1) grammar, the conflict recognition unit 2 recognizes the conflict state that occurs.

If the conflict recognition unit 2 includes a reduction state in the state in which a conflict has occurred, the reduction conflict analysis unit 3 analyzes the reduction conflict,
Display an example of a rule with a reduction conflict and its structure.

Next, with reference to FIG. 2, a description will be given of the main processing flow of the analysis and display method of information regarding the rules of the return state when a return conflict occurs. Let the left-hand side symbol of the above rule be NT,
Let T be the input symbol when a conflict occurs. First, in step 1, a rule with NT on the right side is searched for, and that rule is defined as a rule. If in step 2 NT is the rightmost of the right hand side of the regular ratio, then in step 3 we check whether this rule is already pushed onto the stack, and if so, in step 4 we pop the stack, Return to step 2. If in step 2 NT is not at the rightmost position on the right side of the regular ratio, then in step 5 the symbol immediately to the right of NT on the right side of the regular ratio is set to NTN. In step 6, it is checked whether NTN is the symbol T or whether T is included in the first set of NTN, and when the condition is met, in step 7, the rules pushed onto the stack are displayed and reduced. As competitive analysis information, N from the common ancestor of NTN and T
Displays the path on the syntax tree up to TN. And N.T.
If the symbol T is included in the first set of N,
The path from NTN to symbol T on the syntax tree is also displayed. N
TN is not the symbol T, and T is in the first set of NTN.
If not included, return to step 1. Step 3
If the rule is not pushed onto the stack in step 8, push the current symbol NT and rule R onto the stack, where NT becomes the current general left-hand symbol, and step 1
Return to Here, when searching for a rule having NT on the right side in step l, the already selected rule is not selected.

Next, the flow for the input syntax rule of FIG. 3 will be explained with reference to FIG. The rules generated by the syntax rule analyzer in Figure 3 are 'Nl:T4T5' on the fourth line and 'N2:T4T5' on the fifth line.
:T4 T5", the input symbol where the conflict occurs is T
It is. "Nl:'I'4T5" will be explained. NT in step 1 of FIG. 2 becomes N1 in this case. First, in step 1, a rule having NT on the right side is searched for, and that rule is defined as a rule.几 is @Yl:TINI” on the 2nd line of Figure 3.
becomes. In the check in step 2, in this case, NT(N
l) is the rightmost right-hand side of the rule ("Yl:TlN1'), so it is checked in step 3 whether it is pushed to the stack, and in this case it is not pushed to the stack, so it is checked in step 8. Push N$, I( onto the stack and return to step 1. At this time, N
T is Yl, and in step 1, "x:" in the first line of FIG.
yl y2' is set to 几. In step 2, NT(
Since Yl) is not the rightmost of the right-hand side of R(ゝX:YI Y2'), the NTN in step 5 is 7 to display the path. The displayed result is K as shown in FIG. The first line in Figure 5 is the syntax rule that caused the conflict, the third line is the rule that was pushed onto the stack, the fifth line is the rule that was selected at the start of the display, and the seventh line is the second rule. In figure step 7? By displaying the path from TN to T, the rule is displayed.

〔Effect of the invention〕

As explained above, by using the reduction competition analysis method of the present invention, it becomes possible to display detailed information regarding the reduction competition when a reduction competition occurs, and the 5LRfl
) In the syntax analysis method, it becomes easy to determine the cause of conflict and resolve it.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an embodiment of the reduction conflict analysis method of the present invention, Figure 2 is a diagram showing the processing flow of reduction conflict analysis and reduction conflict information display, and Figure 3 is an input that is not a 5LR (0) grammar. Figures showing examples of syntactic rules. Figure 4 fl) and +2) are diagrams showing examples of syntax trees that cause reductive conflicts in the syntax rules of Figure 3. Figure 5 shows the syntax rules in line 2 of Figure 6. 'Nl:T
A diagram showing an example of analysis information display of the reduction state of 4'l"5',
FIG. 6 is a diagram showing an example of the output of reduction competition information according to the conventional method when the syntax rule as shown in FIG. 3 is input. 1 is a syntax rule analysis section, 2 is a conflict recognition section, and 3 is a reduction conflict analysis section. Agent Patent Attorney Susumu Uchihara Figure 1 BNF Format Syntax Rules Reduction Competitive Information Figure 3 D5 YI TI N1 ↓ X: YI Y2 No. Y2: TI2 Figure 6 reduce/reduc & C0nfliCt OI
L TN1゛N1T5 N2:N4゛5 (2) × / \

Claims (1)

[Claims] In a data structure analysis method that takes a syntax rule given in BNF format as input and performs SLR (1) syntax analysis based on the syntax rule, non-terminal symbols are An example of a syntactic structure in which, when a terminal symbol included in the non-terminal symbol and its follow set is given, a path from the common ancestor of the non-terminal symbol and the terminal symbol is searched on the syntax tree, and a reduction conflict occurs. A reduction competition analysis method characterized by displaying the following.