digitalmars.D - problem with declaration grammar?
- jerry quinn <jlquinn optonline.net> Feb 18 2009
- Christopher Wright <dhasenan gmail.com> Feb 18 2009
- jerry quinn <jlquinn optonline.net> Feb 18 2009
- Christopher Wright <dhasenan gmail.com> Feb 19 2009
- Sergey Gromov <snake.scaly gmail.com> Feb 19 2009
- Ellery Newcomer <ellery-newcomer utulsa.edu> Feb 19 2009
- jerry quinn <jlquinn optonline.net> Feb 19 2009
- Ellery Newcomer <ellery-newcomer utulsa.edu> Feb 19 2009
Hi there, I'm not sure if I'm missing something, but I'm having trouble seeing that a simple declaration will parse correctly with the D grammar. If we take a declaration statment like: int x = 3; we have (my best guess): DeclarationStatement -> Declaration Declaration -> Decl Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator = Initializer Declarator -> BasicType2 Identifier BasicType2 -> ???? I'm thinking that BasicType2 is optional here, rather than required as the grammar shows. Is that correct? Thanks Jerry
Feb 18 2009
jerry quinn wrote:Hi there, I'm not sure if I'm missing something, but I'm having trouble seeing that a simple declaration will parse correctly with the D grammar. If we take a declaration statment like: int x = 3; we have (my best guess): DeclarationStatement -> Declaration Declaration -> Decl Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator = Initializer Declarator -> BasicType2 Identifier BasicType2 -> ???? I'm thinking that BasicType2 is optional here, rather than required as the grammar shows. Is that correct? Thanks Jerry
. Declaration -> Decl . Decl -> BasicType Declarators . BasicType -> "int" . Declarators -> DeclaratorInitializer . DeclaratorInitializer -> Declarator "=" Initializer We agree up to here. . Declarator -> Identifier Here, you don't need BasicType2, and if you use it, you recurse, so using the rule Declarator -> BasicType2 Declarator here is useless. . Identifier -> "x" . Initializer -> ... -> "3"
Feb 18 2009
Christopher Wright Wrote:jerry quinn wrote:Hi there, I'm not sure if I'm missing something, but I'm having trouble seeing that a simple declaration will parse correctly with the D grammar. If we take a declaration statment like: int x = 3; we have (my best guess): DeclarationStatement -> Declaration Declaration -> Decl Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator = Initializer Declarator -> BasicType2 Identifier BasicType2 -> ???? I'm thinking that BasicType2 is optional here, rather than required as the grammar shows. Is that correct? Thanks Jerry
. Declaration -> Decl . Decl -> BasicType Declarators . BasicType -> "int" . Declarators -> DeclaratorInitializer . DeclaratorInitializer -> Declarator "=" Initializer We agree up to here. . Declarator -> Identifier Here, you don't need BasicType2, and if you use it, you recurse, so using the rule Declarator -> BasicType2 Declarator here is useless.
What you describe sounds like what I'd expect. Maybe I'm missing something. The grammar shown in http://www.digitalmars.com/d/2.0/declaration.html has the following rules: BasicType2: * [ ] [ Expression ] [ Expression .. Expression ] [ Type ] delegate Parameters FunctionAttributesopt function Parameters FunctionAttributesopt Declarator: BasicType2 Declarator DeclaratorSuffixesopt BasicType2 Identifier DeclaratorSuffixesopt With this definition, I don't see how you can get Declarator->Identifier. Jerry
Feb 18 2009
Christopher Wright <dhasenan gmail.com> jerry quinn wrote:Christopher Wright Wrote:jerry quinn wrote:Hi there, I'm not sure if I'm missing something, but I'm having trouble seeing that a simple declaration will parse correctly with the D grammar. If we take a declaration statment like: int x = 3; we have (my best guess): DeclarationStatement -> Declaration Declaration -> Decl Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator = Initializer Declarator -> BasicType2 Identifier BasicType2 -> ???? I'm thinking that BasicType2 is optional here, rather than required as the grammar shows. Is that correct? Thanks Jerry
. Decl -> BasicType Declarators . BasicType -> "int" . Declarators -> DeclaratorInitializer . DeclaratorInitializer -> Declarator "=" Initializer We agree up to here. . Declarator -> Identifier Here, you don't need BasicType2, and if you use it, you recurse, so using the rule Declarator -> BasicType2 Declarator here is useless.
What you describe sounds like what I'd expect.
It's from the 1.0 grammar.Maybe I'm missing something. The grammar shown in http://www.digitalmars.com/d/2.0/declaration.html has the following rules:
That looks to be in error.
Feb 19 2009
Thu, 19 Feb 2009 01:30:36 -0500, jerry quinn wrote:Christopher Wright Wrote:jerry quinn wrote:Hi there, I'm not sure if I'm missing something, but I'm having trouble seeing that a simple declaration will parse correctly with the D grammar. If we take a declaration statment like: int x = 3; we have (my best guess): DeclarationStatement -> Declaration Declaration -> Decl Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator = Initializer Declarator -> BasicType2 Identifier BasicType2 -> ???? I'm thinking that BasicType2 is optional here, rather than required as the grammar shows. Is that correct? Thanks Jerry
. Declaration -> Decl . Decl -> BasicType Declarators . BasicType -> "int" . Declarators -> DeclaratorInitializer . DeclaratorInitializer -> Declarator "=" Initializer We agree up to here. . Declarator -> Identifier Here, you don't need BasicType2, and if you use it, you recurse, so using the rule Declarator -> BasicType2 Declarator here is useless.
What you describe sounds like what I'd expect. Maybe I'm missing something. The grammar shown in http://www.digitalmars.com/d/2.0/declaration.html has the following rules: BasicType2: * [ ] [ Expression ] [ Expression .. Expression ] [ Type ] delegate Parameters FunctionAttributesopt function Parameters FunctionAttributesopt Declarator: BasicType2 Declarator DeclaratorSuffixesopt BasicType2 Identifier DeclaratorSuffixesopt With this definition, I don't see how you can get Declarator->Identifier. Jerry
The grammar works the other way around: int x = 3 ; int -> BasicType(int) // this is either Decl or Type, need more tokens, expect Declarators, // Declarator, or Declarator2 ----- x -> Identifier(x) // either DeclaratorInitializer (Declarators), Declarator, // IdentifierList (not expecting), StructMemberInitializer (not // expecting), or PrimaryExpression (not expecting) // therefore expecting '=' or DeclaratorSuffixes ----- = -> = // token // Identifier(x) = -> definitely DeclaratorInitializer, expecting // Initializer, that is , either void, AssignExpression, // ArrayInitializer, or StructInitializer ----- 3 -> IntegerLiteral(3) -> PrimaryExpression(3) // may be some sort of other expression, need more tokens ----- ; -> ; // token // not a part of an expression ----- PrimaryExpression(3) -> AssignExpression(3) Identifier(x) = AssignExpression(3) -> DeclaratorInitializer(x=3) // DeclaratorInitializer(x=3) is Declarators, expect ',' but actually // have ';' next, so DeclaratorInitializer(x=3) -> Declarators(x=3) ----- BasicType(int) DeclaratorInitializer(x=3) ; -> Decl(int x=3;) Finita la comedia.
Feb 19 2009
jerry quinn wrote:Christopher Wright Wrote:jerry quinn wrote:Hi there, I'm not sure if I'm missing something, but I'm having trouble seeing that a simple declaration will parse correctly with the D grammar. If we take a declaration statment like: int x = 3; we have (my best guess): DeclarationStatement -> Declaration Declaration -> Decl Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator = Initializer Declarator -> BasicType2 Identifier BasicType2 -> ???? I'm thinking that BasicType2 is optional here, rather than required as the grammar shows. Is that correct? Thanks Jerry
. Decl -> BasicType Declarators . BasicType -> "int" . Declarators -> DeclaratorInitializer . DeclaratorInitializer -> Declarator "=" Initializer We agree up to here. . Declarator -> Identifier Here, you don't need BasicType2, and if you use it, you recurse, so using the rule Declarator -> BasicType2 Declarator here is useless.
What you describe sounds like what I'd expect. Maybe I'm missing something. The grammar shown in http://www.digitalmars.com/d/2.0/declaration.html has the following rules: BasicType2: * [ ] [ Expression ] [ Expression .. Expression ] [ Type ] delegate Parameters FunctionAttributesopt function Parameters FunctionAttributesopt Declarator: BasicType2 Declarator DeclaratorSuffixesopt BasicType2 Identifier DeclaratorSuffixesopt With this definition, I don't see how you can get Declarator->Identifier. Jerry
You are correct. BasicType2 can match nothing. It should also be able to match what it does above multiple times.
Feb 19 2009
Ellery Newcomer Wrote:Maybe I'm missing something. The grammar shown in http://www.digitalmars.com/d/2.0/declaration.html has the following rules: BasicType2: * [ ] [ Expression ] [ Expression .. Expression ] [ Type ] delegate Parameters FunctionAttributesopt function Parameters FunctionAttributesopt Declarator: BasicType2 Declarator DeclaratorSuffixesopt BasicType2 Identifier DeclaratorSuffixesopt With this definition, I don't see how you can get Declarator->Identifier. Jerry
You are correct. BasicType2 can match nothing. It should also be able to match what it does above multiple times.
As I'm looking at this further, there seems to be more issues. In particular, I don't think the grammar can parse: int (*x)(char); as specified. Doing so gives (my best attempt) Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator Declarator -> BasicType2 Identifier DeclaratorSuffixes BasicType2 -> NULL (assuming that the grammar should be revised like this) Identifier -> BAD PARSE
Feb 19 2009
jerry quinn wrote:Ellery Newcomer Wrote:Maybe I'm missing something. The grammar shown in http://www.digitalmars.com/d/2.0/declaration.html has the following rules: BasicType2: * [ ] [ Expression ] [ Expression .. Expression ] [ Type ] delegate Parameters FunctionAttributesopt function Parameters FunctionAttributesopt Declarator: BasicType2 Declarator DeclaratorSuffixesopt BasicType2 Identifier DeclaratorSuffixesopt With this definition, I don't see how you can get Declarator->Identifier. Jerry
match what it does above multiple times.
As I'm looking at this further, there seems to be more issues. In particular, I don't think the grammar can parse: int (*x)(char); as specified. Doing so gives (my best attempt) Decl -> BasicType Declarators ; BasicType -> int Declarators -> DeclaratorInitializer DeclaratorInitializer -> Declarator Declarator -> BasicType2 Identifier DeclaratorSuffixes BasicType2 -> NULL (assuming that the grammar should be revised like this) Identifier -> BAD PARSE
yeah, if you haven't figured out by now, the grammar is a bunch of hooey. I spent like a month building an ANTLR grammar based on the above, and then realized much of it was garbage. Then I spent two months going through the source code and rewriting most of the rules. Just got done with it a week or two ago :) That was all version 1, but it looks the same, so if memory serves the above rules should look something like this: BasicType2_x: * [ ] [ Expression ] [ Expression .. Expression ] [ Type ] delegate Parameters FunctionAttributesopt function Paramters FunctionAttributesopt BasicType2: BasicType2_x BasicType2 BasicType2_x epsilon Declarator: BasicType2 Identifier DeclaratorSuffixesopt BasicType2 ( Declarator ) DeclaratorSuffixesopt Apologies for any BNF misuse
Feb 19 2009