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Re: Updated SRFI-110 posted.

This page is part of the web mail archives of SRFI 110 from before July 7th, 2015. The new archives for SRFI 110 contain all messages, not just those from before July 7th, 2015.

David A. Wheeler scripsit:

> Thoughts?

Below is a version with no Java cruft, which I find more readable.

// Production "collecting_content" returns a collecting list's contents.
// Precondition: After collecting start and horizontal spaces.
// Postcondition: Consumed the matching COLLECTING_END.
// FF  formfeed (\f aka \u000c), VT  vertical tab (\v aka \u000b)

  : it_expr collecting_content
  | comment_eol    collecting_content
  | (FF | VT)+ EOL collecting_content

  : COLLECTING hs collecting_content hs;

// Process line after ". hspace+" sequence.  Does not go past current line.

  : skippable post_period
    | n_expr hs skippable* (n_expr error)?
    | collecting_list skippable* (n_expr error)?
    | /*empty*/;

// Production "line_exprs" reads the 1+ n-expressions on one line; it will
// return the list of n-expressions on the line.  If there is one n-expression
// on the line, it returns a list of exactly one item.
// Precondition: At beginning of line after indent
// Postcondition: At unconsumed EOL

  : PERIOD /* Leading ".": escape following datum like an n-expression. */
      (hspace+ post_period
       | /*empty*/)
  | collecting_list
       | /*empty*/)
  | n_expr_first /* Only match n_expr_first */
      ((hspace+ (rest_of_line 
                 | /*empty*/))
       | /*empty*/);

// Production "rest_of_line" reads the rest of the expressions on a line,
// after the first expression of the line.
// Precondition: At beginning of non-first expression on line (past hspace)
// Postcondition: At unconsumed EOL

  : PERIOD hspace+ post_period /* Improper list */
  | skippable (rest_of_line | /*empty*/)
  | collecting_list
     | /*empty*/)
  | n_expr
      ((hspace+ (rest_of_line
                 | /*empty*/))
       | /*empty*/);

// Production "body" handles the sequence of 1+ child lines in an it_expr
// (e.g., after "line_expr"), each of which is itself an it_expr.
// It returns the list of expressions in the body.

  : it_expr
       (? >   it_expr DEDENT // Improper list
       |? > body    
       |? > body)
     | DEDENT);

// Production "normal_it_expr" is an it_expr without a special prefix.

normal_it_expr returns [Object v] 
  : line_exprs (
     GROUP_SPLIT hs // split
     | SUBLIST hs it_expr
     | comment_eol // Normal case, handle child lines if any:
       (INDENT body
        | /*empty*/ /* No child lines */));

// These are it_expr's with a special prefix like \\ or $:

    (it_expr | comment_eol INDENT body);

  : (GROUP_SPLIT | scomment) hs /* Initial; Interpet as group */
      (it_expr /* Ignore initial GROUP/scomment */
       | comment_eol
         (INDENT body /* Normal GROUP use */
          | /*empty*/));

sublist_line returns [Object v] // "$" first on line
  : SUBLIST hs it_expr;

  : abbrevw hs
      (comment_eol INDENT body
       | it_expr);

// Production "it_expr" (indenting sweet-expression)
// is the main production for sweet-expressions in the usual case.
// Precondition: At beginning of line after indent, NOT at an EOL char
// Postcondition: it-expr ended by consuming EOL + examining indent

  : normal_it_expr    
  | datum_comment_line
  | group_line        
  | sublist_line      
  | abbrevw_line      ;

// Production "initial_indent_expr" is for an expression starting with indent.

  : (INITIAL_INDENT | separator_initial_indent) (scomment hs)*
     | comment_eol);

// Production "t_expr_real" handles special cases, else it invokes it_expr.

  : comment_eol    r1t_expr_real // Skip initial blank lines
  | (FF | VT)+ EOL r2t_expr_real // Skip initial FF|VT lines
  | EOF                           // End of file
  | initial_indent_expr          
  | it_expr                     /* Normal case */;

// Production "t_expr" is the top-level production for sweet-expressions.

  : t_expr_real	
      ; retry if empty_value.

Is a chair finely made tragic or comic? Is the          John Cowan
portrait of Mona Lisa good if I desire to see           cowan@xxxxxxxx
it? Is the bust of Sir Philip Crampton lyrical,         http://ccil.org/~cowan
epical or dramatic?  If a man hacking in fury
at a block of wood make there an image of a cow,
is that image a work of art? If not, why not?               --Stephen Dedalus