xtext中的终端/数据类型/解析器规则 [英] terminal/datatype/parser rules in xtext

问题描述

我正在使用xtext 2.4. 我想做的是一种类似SQL的语法. 让我感到困惑的是，我不确定应该将哪些东西视为终端/数据类型/解析器规则.到目前为止，我与MyTerm相关的语法是:

I'm using xtext 2.4. What I want to do is a SQL-like syntax. The things confuse me are I'm not sure which things should be treated as terminal/datatype/parser rules. So far my grammar related to MyTerm is:

Model:
    (terms += MyTerm ';')*
;

MyTerm:
    constant=MyConstant | variable?='?'| collection_literal=CollectionLiteral 
;

MyConstant
    : string=STRING 
    | number=MyNumber
    | date=MYDATE 
    | uuid=UUID 
    | boolean=MYBOOLEAN
    | hex=BLOB
;

MyNumber:
    int=SIGNINT | float=SIGNFLOAT
;


SIGNINT returns ecore::EInt:
    '-'? INT
;


SIGNFLOAT returns ecore::EFloat:
    '-'? INT '.' INT;
;

CollectionLiteral:
    => MapLiteral | SetLiteral | ListLiteral
;

MapLiteral:
    '{' {MapLiteral} (entries+=MapEntry (',' entries+=MapEntry)* )? '}'
;

MapEntry:
    key=MyTerm ':' value=MyTerm
;

SetLiteral:
    '{' {SetLiteral} (values+=MyTerm (',' values+=MyTerm)* )+ '}'
;

ListLiteral:
    '[' {ListLiteral} ( values+=MyTerm (',' values+=MyTerm)* )? ']'
;

terminal MYDATE:
  '0'..'9' '0'..'9' '0'..'9' '0'..'9' '-'
  '0'..'9' '0'..'9' '-'
  '0'..'9' '0'..'9'
;

terminal HEX:
    'a'..'h'|'A'..'H'|'0'..'9'
;   

terminal UUID:
    HEX HEX HEX HEX HEX HEX HEX HEX '-'
    HEX HEX HEX HEX '-'
    HEX HEX HEX HEX '-'
    HEX HEX HEX HEX '-'
    HEX HEX HEX HEX HEX HEX HEX HEX HEX HEX HEX HEX
;

terminal BLOB:
    '0' ('x'|'X') HEX+
;

terminal MYBOOLEAN returns ecore::EBoolean:
    'true' | 'false' | 'TRUE' | 'FALSE'
;

几个问题:

• 如何用符号定义整数?如果我定义另一个终端规则terminal SIGNINT: '-'? '0'..'9'+;，则antlr将抱怨INT无法访问.因此，我将其定义为数据类型规则SIGNINT: '-'? INT;这是正确的方法吗?

• How to define integer with sign? If I define another terminal rule terminal SIGNINT: '-'? '0'..'9'+;, antlr will complain about INT becoming unreachable. Therefore I define it as a datatype rule SIGNINT: '-'? INT; Is this the correct way to do it?

如何用符号定义浮点数?我做的和定义带符号SIGNFLOAT: '-'? INT '.' INT;的整数完全一样，不确定这是否正确.

How to define float with sign? I did exactly the same as define integer with sign, SIGNFLOAT: '-'? INT '.' INT;, not sure if this is correct as well.

如何定义日期规则?我想使用解析器规则在字段中存储年/月/日信息，但将其定义为MyDate: year=INT '-' month=INT '-' date=INT; antlr会抱怨Decision can match input such as "RULE_INT '-' RULE_INT '-' RULE_INT" using multiple alternatives: 2, 3 As a result, alternative(s) 3 were disabled for that input

How to define a date rule? I want to use a parser rule to store year/month/day info in fields, but define it as MyDate: year=INT '-' month=INT '-' date=INT; antlr will complain Decision can match input such as "RULE_INT '-' RULE_INT '-' RULE_INT" using multiple alternatives: 2, 3 As a result, alternative(s) 3 were disabled for that input

我还有其他一些规则，例如

I also have some other rules like

以下

RelationCompare:
    name=ID compare=COMPARE term=MyTerm
;

，但a=4将不是有效的RelationCompare，因为a和4将被视为HEX.我发现这是因为，如果我将关系更改为j=44，那么它将起作用.在此帖子中说终端规则定义的eariler将遮盖以后定义的规则.但是，如果我在语法中重新定义terminal ID，无论将其放在terminal HEX的前面还是后面，antlr都会表示The following token definitions can never be matched because prior tokens match the same input: RULE_HEX,RULE_MYBOOLEAN. k=0x00b中也会发生此问题. k=0xaab有效，但k=0x00b无效.

but a=4 won't be a valid RelationCompare because a and 4 will be treat as HEXs. I found this because if I change the relation to j=44 then it works. In this post it said terminal rule defined eariler will shadow those defined later. However, if I redefine terminal ID in my grammar, whether put it in front or after of terminal HEX, antlr will conplain The following token definitions can never be matched because prior tokens match the same input: RULE_HEX,RULE_MYBOOLEAN. This problem happens in k=0x00b as well. k=0xaab is valid but k=0x00b is not.

有什么建议吗?

推荐答案

稍后，我找到了想要的原始antlr语法，因此我只是将antlr语法转换为xtext语法.这是我定义这些基本类型的方法:

Later I found the original antlr grammar for what I want to do therefore I simply translate the antlr grammar to xtext grammar. Here is how I defining those basic types:

terminal fragment A: 'a'|'A';  
   ... 
terminal fragment Z: 'z'|'Z';

terminal fragment DIGIT: '0'..'9';
terminal fragment LETTER: ('a'..'z'|'A'..'Z');
terminal fragment HEX: ('a'..'f'|'A'..'F'|'0'..'9'); 

terminal fragment EXPONENT: E ('+'|'-')? DIGIT+;
terminal INTEGER returns ecore::EInt: '-'? DIGIT+;
terminal FLOAT returns ecore::EFloat: INTEGER EXPONENT | INTEGER '.' DIGIT* EXPONENT?;

terminal BOOLEAN: T R U E | F A L S E;

原始语法中的日期规则被视为字符串.

The Date rule in original grammar is treated as a string.

关于规则名称(规则:Antlr语法=> xtext语法)

About rules name (Rules: Antlr Grammar => xtext Grammar)

• 解析器规则:以小写字母开头=>以大写字母开头的规则(每个都是Java类)
• 终端规则:以大写字母=>开头，并使用所有带有terminal前缀的大写字母
• 片段终端规则:fragment ID => terminal fragment ID

• parser rule: starting with lowercase => rules starting with uppercase (each will be a Java Class)
• terminal rule: starting with uppercase => using all uppercase with terminal prefix
• fragment terminal rule: fragment ID => terminal fragment ID

在antlr中，这样定义参数列表:

In antlr a list of arguments is defined like this:

functionArgs
  : '(' ')'
  | '(' t1=term ( ',' tn=term )* ')'
;

相应的xtext语法为:

The corresponding xtext grammar is:

FunctionArgs
 : '(' ')'
 | '(' ts+=Term  (',' ts+=Term )* ')'
;

对于带有[ ]

properties[PropertyDefinitions props]
  : property[props] (K_AND property[props])*
;

大多数情况下，它们可以移动到左侧

Most of the time they could be moved to the left hand side

Properties
  : props+=Property (K_AND props+=Property)*
;

现在它可以正常工作了.

Now it's working as expected.

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