使用BNFC确定命题逻辑的基本语言(语法错误) [英] Using BNFC to determine a basic language for propositional logic (syntax error)
问题描述
我想使用BNFC解析命题逻辑中的句子.我编写了以下BNF语法来简化此操作:
I would like to parse sentences in propositional logic using BNFC. I wrote the following BNF grammar to facilitate this:
Negation. N ::= "(" "-" L")";
Conjuction. C ::= "(" L "&" L ")";
Disjuction. D ::= "(" L "|" L ")";
Implication. I ::= "(" L "=>" L ")";
Equivalence. E ::= "(" L "<=>" L ")";
Atom. L ::= Ident | N | C | D | I | E ;
但是，通过这种构造，我得到以下错误:
However, with this construction I get the following error:
syntax error at line 6, column 27 before `|'
我提供的规范在语法上有何不正确?
What is syntactically incorrect about the specification I provided?
好，所以看起来bnfc真的不喜欢使用符号|进行联合的想法.然后，如果不通过联合，如何将多个生产分配给单个规则?我不想定义Atom1. L ::= Ident ;，Atom2. L ::= N ;等，但是如果我想使它起作用，这是否有必要?
Ok, so it looks like bnfc really does not like the idea of using the symbol | for union. How do I then assign multiple productions to a single rule, if not via a union? I do not want to have to define Atom1. L ::= Ident ;, Atom2. L ::= N ; and so forth, but is this necessary if I want this to work?
好，所以给每个L产品赋予不同的标签，如
Ok, so giving different labels to each L-production, as in
Negation. N ::= "(" "-" L")";
Conjuction. C ::= "(" L "&" L ")";
Disjuction. D ::= "(" L "|" L ")";
Implication. I ::= "(" L "=>" L ")";
Equivalence. E ::= "(" L "<=>" L ")";
Atom1. L ::= Ident ;
Atom2. L ::= N ;
Atom3. L ::= C ;
Atom4. L ::= D ;
Atom5. L ::= I ;
Atom6. L ::= E ;
允许文件logic.cf通过bnfc而没有任何错误.但是，使用命令编译文件时
allowed the file logic.cf to pass through bnfc without any errors. However, when the file is compiled using the command
bnfc -m -c file.cf
然后我尝试运行make，当Make尝试在bnfc生成的文件Printer.c上运行gcc时，出现以下错误:
and I then try running make, I get the following error when Make tries to run gcc on the bnfc-generated file Printer.c:
gcc -g -W -Wall -c Absyn.c
flex -Plogic -oLexer.c logic.l
gcc -g -W -Wall -c Lexer.c
Lexer.c:1477:16: warning: ‘input’ defined but not used [-Wunused-function]
static int input (void)
^~~~~
Lexer.c:1434:17: warning: ‘yyunput’ defined but not used [-Wunused-function]
static void yyunput (int c, char * yy_bp )
^~~~~~~
bison -t -plogic logic.y -o Parser.c
gcc -g -W -Wall -c Parser.c
gcc -g -W -Wall -c Printer.c
Printer.c: In function ‘ppL’:
Printer.c:289:20: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
ppIdent(_p_->u.atom_.ident_, 0);
^~~~~
atom1_
Printer.c:296:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
ppN(_p_->u.atom_.n_, 0);
^~~~~
atom1_
Printer.c:303:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
ppC(_p_->u.atom_.c_, 0);
^~~~~
atom1_
Printer.c:310:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
ppD(_p_->u.atom_.d_, 0);
^~~~~
atom1_
Printer.c:317:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
ppI(_p_->u.atom_.i_, 0);
^~~~~
atom1_
Printer.c:324:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
ppE(_p_->u.atom_.e_, 0);
^~~~~
atom1_
Printer.c: In function ‘ppInteger’:
Printer.c:336:31: warning: unused parameter ‘i’ [-Wunused-parameter]
void ppInteger(Integer n, int i)
^
Printer.c: In function ‘ppDouble’:
Printer.c:342:29: warning: unused parameter ‘i’ [-Wunused-parameter]
void ppDouble(Double d, int i)
^
Printer.c: In function ‘ppChar’:
Printer.c:348:25: warning: unused parameter ‘i’ [-Wunused-parameter]
void ppChar(Char c, int i)
^
Printer.c: In function ‘ppString’:
Printer.c:354:29: warning: unused parameter ‘i’ [-Wunused-parameter]
void ppString(String s, int i)
^
Printer.c: In function ‘ppIdent’:
Printer.c:360:28: warning: unused parameter ‘i’ [-Wunused-parameter]
void ppIdent(String s, int i)
^
Printer.c: In function ‘shL’:
Printer.c:507:20: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
shIdent(_p_->u.atom_.ident_);
^~~~~
atom1_
Printer.c:522:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
shN(_p_->u.atom_.n_);
^~~~~
atom1_
Printer.c:537:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
shC(_p_->u.atom_.c_);
^~~~~
atom1_
Printer.c:552:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
shD(_p_->u.atom_.d_);
^~~~~
atom1_
Printer.c:567:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
shI(_p_->u.atom_.i_);
^~~~~
atom1_
Printer.c:582:16: error: ‘union <anonymous>’ has no member named ‘atom_’; did you mean ‘atom1_’?
shE(_p_->u.atom_.e_);
^~~~~
atom1_
Makefile:42: recipe for target 'Printer.o' failed
make: *** [Printer.o] Error 1
我不知道这意味着什么.为什么在我未在logic.cf中指定此类内容的情况下尝试找到atom_，如果有人对bnfc的内部知识有更深入的了解，我不会介意您的来信.
I have no idea what this means. Why is it trying to find atom_, when I've not specified such a thing in logic.cf If there are any people more experienced with the internals of bnfc, I wouldn't mind hearing from you.
好，所以将标签写为
Negation. N ::= "(" "-" L ")";
Conjuction. C ::= "(" L "&" L ")";
Disjuction. D ::= "(" L "|" L ")";
Implication. I ::= "(" L "=>" L ")";
Equivalence. E ::= "(" L "<=>" L ")";
Atom. L ::= Ident;
AtomN. L ::= N ;
AtomC. L ::= C ;
AtomD. L ::= D ;
AtomI. L ::= I ;
AtomE. L ::= E ;
以某种方式神奇地允许make通过.但是，我的解析器不能完全正常工作，就像这样简单
somehow magically allowed make to pass. However, my parser isn't exactly working, as something as simple as
echo "p" | ./Testlogic
返回
error: line 1: syntax error at p
p不是有效的标识符，因此生产版本Atom. L ::= Ident;应该允许它通过吗?为什么不是这种情况?
Isn't p a valid identifier, and so the production Atom. L ::= Ident; should allow it to pass? Why is this not the case?
推荐答案
事实证明，就制作顺序而言，BNFC有点挑剔.我不得不写
It turns out BNFC is a bit picky, when it comes to the order of the productions. I had to write
Atom. L ::= Ident;
AtomN. L ::= N ;
AtomC. L ::= C ;
AtomD. L ::= D ;
AtomI. L ::= I ;
AtomE. L ::= E ;
Negation. N ::= "(" "-" L ")";
Conjuction. C ::= "(" L "&" L ")";
Disjuction. D ::= "(" L "|" L ")";
Implication. I ::= "(" L "=>" L ")";
Equivalence. E ::= "(" L "<=>" L ")";
除了去除标签末尾的数字以使其起作用外.我现在可以用谓词逻辑解析简单的句子:
in addition to getting rid of the numbers at the ends of the labels to make it work. I am now able to parse simple sentences in predicate logic:
$ echo "(a&(a<=>b))" | ./Testlogic
Parse Succesful!
[Abstract Syntax]
(AtomC [(Conjuction (Atom ["a"]) (AtomE [(Equivalence (Atom ["a"]) (Atom ["b"]))]))])
[Linearized Tree]
(a & (a <=> b))
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