Re: [PATCH olang v1 2/2] docs: spec: add variables and constants specification

["Carlos Maniero" <carlos@maniero.me>]

On Wed Mar 27, 2024 at 6:37 PM -03, Johnny Richard wrote:
> On Wed, Mar 27, 2024 at 12:21:28AM -0300, Carlos Maniero wrote:
> > This commit introduces the specification for variables and constants. A
> > valid program under this specification is as follows:
> > 
> >   var x: u32 = 1
>
> Since this patch adds support to assignments, lets also add support to
> all assignment operators like "-=" "+=" "<<=" and so on.
>
> >   const y: u32 = 2
>
> This patch lacks support to the following valid assignment expression
> (which I think adds flexibility to the language):
>
>     var x: u32 = a = b = c = 1
>     var y: u32
>     y = a = b = c = 1
>
> > -<global-statements>   ::= <function-definition>
> > +<global-statements>   ::= <function-definition> | <variable-definition> | <variable-reassign> | <const-definition>
>
> nitpick: maybe _external-declaration_ sounds better since definitions are
> not statements?

What do you think about *file-declarations* a file declaration? Does not
mean that it is external. At least while we try to define a file.

>
> > +
> > +(* Variables *)
> > +<variable-definition> ::= 'var' <ws> <variable-name> <ows> ':' <ows> <type> <ows> <variable-assign>?
> > +<const-definition>    ::= 'const' <ws> <variable-name> <ows> ':' <ows> <type> <ows> <variable-assign>
>
> We don't need to define twice the variable-definition for "var" and
> "const", let's combine both in a single rule.

I don't know if you noticed, but variables has an optional assignment
while const has required assignment.
>
> > +<variable-name>       ::= <identifier>
> > +<variable-assign>     ::= '=' <ows> <expression>
> > +<variable-reassign>   ::= <variable-name> <ows> <variable-assign> <end-of-statement>
> >  
> >  (* Functions *)
> >  <function-definition> ::= 'fn' <ws> <function-name> <ows>
> > @@ -38,11 +46,11 @@ language.
> >  <block>               ::= '{' <ows> <statement> <ows> (<end-of-statement>
> >  <ows> <statement> <ows>)* <end-of-statement>? <ows> '}'
> >  <end-of-statement>    ::= ';' | <line-break> | <end-of-file>
> > -<statement>           ::= <return-statement>
> > +<statement>           ::= <return-statement> | <variable-definition> | <variable-reassign> | <const-definition>
> >  <return-statement>    ::= 'return' <ws> <expression>
> >  
> >  (* Expressions *)
> > -<expression>          ::= <integer>
> > +<expression>          ::= <integer> | <identifier>
> >  
> >  (* Identifiers *)
> >  <type>                ::= 'u32'
> > -- 
> > 2.34.1
> > 
>
> I have done few adjustments according to my feedback (I also fix the
> unnecessary line breaks on function and block).  Let me know what you
> think about it.
>
> ---->8----
> Subject: [PATCH olang] fixup! docs: spec: add variables and constants specification
>
>
> diff --git a/docs/pages/language-specification.md b/docs/pages/language-specification.md
> index 708b679..2650dd9 100644
> --- a/docs/pages/language-specification.md
> +++ b/docs/pages/language-specification.md
> @@ -22,35 +22,45 @@ language.
>  
>  ```
>  (* Entry Point *)
> -<translation-unit>    ::= <ows> (<global-statements> <end-of-statement>)*
> +<translation-unit>     ::= (<ows> <external-declaration> <ows> (<end-of-statement> | <end-of-file>))*
Way more elegant! Thanks.
>  
> -<global-statements>   ::= <function-definition> | <variable-definition> | <variable-reassign> | <const-definition>
> +<external-declaration> ::= <function-definition> 
> +                         | <variable-definition>
> +                         | <assign-expression>
>  
>  (* Variables *)
> -<variable-definition> ::= 'var' <ws> <variable-name> <ows> ':' <ows> <type> <ows> <variable-assign>?
> -<const-definition>    ::= 'const' <ws> <variable-name> <ows> ':' <ows> <type> <ows> <variable-assign>
> -
> -<variable-name>       ::= <identifier>
> -<variable-assign>     ::= '=' <ows> <expression>
> -<variable-reassign>   ::= <variable-name> <ows> <variable-assign> <end-of-statement>
> +<variable-definition>  ::= <variable-qualifier> <ws> <variable-name> <ows> ':' <ows> <type> (<ows> <assign-operator> <ows> <expression>)?
This is invalid for const unless we want to allow unassigned constants.
It also can be interpreted as a semantic error, in that case I believe
the spec should not check for semantics.
> +<variable-qualifier>   ::= 'var'
> +                         | 'const'
> +<variable-name>        ::= <identifier>
>  
>  (* Functions *)
> -<function-definition> ::= 'fn' <ws> <function-name> <ows>
> -<function-parameters> <ows> ':' <ows> <return-type> <ows> <function-body>
> +<function-definition> ::= 'fn' <ws> <function-name> <ows> <function-parameters> <ows> ':' <ows> <return-type> <ows> <function-body>
>  <function-name>       ::= <identifier>
>  <function-parameters> ::= '(' <ows> ')'
>  <return-type>         ::= <type>
>  <function-body>       ::= <block>
>  
>  (* Statements *)
> -<block>               ::= '{' <ows> <statement> <ows> (<end-of-statement>
> -<ows> <statement> <ows>)* <end-of-statement>? <ows> '}'
> -<end-of-statement>    ::= ';' | <line-break> | <end-of-file>
> -<statement>           ::= <return-statement> | <variable-definition> | <variable-reassign> | <const-definition>
> +<block>               ::= '{' <ows> <statement> <ows> (<end-of-statement> <ows> <statement> <ows>)* <end-of-statement>? <ows> '}'
> +<end-of-statement>    ::= ';' | <line-break>
> +<statement>           ::= <return-statement> | <variable-definition> | <assign-expression>
>  <return-statement>    ::= 'return' <ws> <expression>
>  
>  (* Expressions *)
> -<expression>          ::= <integer> | <identifier>
> +<expression>          ::= <integer> | <identifier> | <assign-expression>
> +<assign-expression>   ::= <variable-name> <ows> <assign-operator> <ows> <expression>
> +<assign-operator>     ::= '='
> +                        | '*='
> +                        | '/='
> +                        | '%='
> +                        | '+='
> +                        | '-='
> +                        | '<<='
> +                        | '>>='
> +                        | '&='
> +                        | '^='
> +                        | '|='
>  
>  (* Identifiers *)
>  <type>                ::= 'u32'