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yhirose 2021-01-21 14:29:55 -05:00
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@ -523,8 +523,9 @@ The custom message supports `%t` which is a place holder for the unexpected toke
Here is an example of Java-like grammar:
```peg
# java.peg
Prog ← 'public' 'class' NAME '{' 'public' 'static' 'void' 'main' '(' 'String' '[' ']' NAME ')' BlockStmt '}'
BlockStmt ← '{' (!'}' Stmt^stmtb)* '}'^rcblk # Annotated with `stmtb` and `rcblk`
BlockStmt ← '{' (!'}' Stmt^stmtb)* '}' # Annotated with `stmtb`
Stmt ← IfStmt / WhileStmt / PrintStmt / DecStmt / AssignStmt / BlockStmt
IfStmt ← 'if' '(' Exp ')' Stmt ('else' Stmt)?
WhileStmt ← 'while' '(' Exp^condw ')' Stmt # Annotated with `condw`
@ -544,13 +545,9 @@ NAME ← < [a-zA-Z_][a-zA-Z_0-9]* >
%word ← NAME
# Recovery operator labels
rcblk ← SkipToRCUR { message "missing end of block." }
semia ← '' { message "missing simicolon in assignment." }
stmtb ← (!(Stmt / 'else' / '}') .)* { message "invalid statement" }
condw ← &'==' ('==' RelExp)* / &'<' ('<' AddExp)* / (!')' .)*
# Recovery expressions
SkipToRCUR ← (!'}' ('{' SkipToRCUR / .))* '}'
```
For instance, `';'^semi` is a syntactic sugar for `(';' / %recovery(semi))`. `%recover` operator tries to recover the error at ';' by skipping input text with the recovery expression `semi`. Also `semi` is assosiated with a custom message "missing simicolon in assignment.".
@ -558,6 +555,7 @@ For instance, `';'^semi` is a syntactic sugar for `(';' / %recovery(semi))`. `%r
Here is the result:
```java
> cat sample.java
public class Example {
public static void main(String[] args) {
int n = 5;
@ -569,10 +567,8 @@ public class Example {
System.out.println(f);
}
}
```
```
> peglint sample_java.peg sample.java
> peglint java.peg sample.java
sample.java:5:12: syntax error, unexpected '<', expecting <NAME>, <NUMBER>, <WhileStmt>.
sample.java:8:5: missing simicolon in assignment.
sample.java:8:6: invalid statement