New range type, distinct from cons cell.

* eval.c (eval_init): Register intrinsic functions rcons,
rangep from and to.
(eval_init): Register rangep intrinsic.

* gc.c (mark_obj): Traverse RNG objects.
(finalize): Handle RNG in switch.

* hash.c (equal_hash, eql_hash): Hashing for for RNG objects.

* lib.c (range_s, rcons_s): New symbol variables.
(code2type): Handle RNG type.
(eql, equal): Equality for ranges.
(less_tab_init): Table extended to cover RNG.
(less): Semantics defined for ranges.
(rcons, rangep, from, to): New functions.
(obj_init): range_s and rcons_s variables initialized.
(obj_print_impl): Produce #R notation for ranges.
(generic_funcall, dwim_set): Recognize range objects for indexing

* lib.h (enum type): New enum member, RNG.  MAXTYPE redefined
to RNG value.
(TYPE_SHIFT): Increased to 5 since there are now 16 type
codes.
(struct range): New struct type.
(union obj): New member rn, of type struct range.
(range_s, rcons_s, rcons, rangep, from, to): Declared.
(range_bind): New macro.

* parser.l (grammar): New rule for recognizing
the #R sequence as HASH_R token.

* parser.y (HASH_R): New terminal symbol.
(range): New nonterminal symbol.
(n_expr): Derives the new range symbol.
The n_expr DOTDOT n_expr rule produces rcons expression rather
than const.

* match.c (format_field): Recognize rcons syntax in fields
which is now what ranges translate to.  Also recognize range
object.

* tests/013/maze.tl (neigh): Fix code which destructures
range as a cons. That can't be done any more.

* txr.1: Document ranges.

1 files changed, 14 insertions, 3 deletions

diff --git a/parser.y b/parser.y
index 0208386d..d63eba4f 100644
--- a/parser.y
+++ b/parser.y
@@ -100,7 +100,7 @@ int yyparse(scanner_t *, parser_t *);
 %token <lineno> UNTIL COLL OUTPUT REPEAT REP SINGLE FIRST LAST EMPTY
 %token <lineno> MOD MODLAST DEFINE TRY CATCH FINALLY
 %token <lineno> ERRTOK /* deliberately not used in grammar */
-%token <lineno> HASH_BACKSLASH HASH_SLASH DOTDOT HASH_H HASH_S
+%token <lineno> HASH_BACKSLASH HASH_SLASH DOTDOT HASH_H HASH_S HASH_R
 %token <lineno> WORDS WSPLICE QWORDS QWSPLICE
 %token <lineno> SECRET_ESCAPE_R SECRET_ESCAPE_E
 
@@ -116,7 +116,7 @@ int yyparse(scanner_t *, parser_t *);
 %type <val> output_clause define_clause try_clause catch_clauses_opt
 %type <val> if_clause elif_clauses_opt else_clause_opt
 %type <val> line elems_opt elems clause_parts_h additional_parts_h
-%type <val> text texts elem var var_op modifiers vector hash struct
+%type <val> text texts elem var var_op modifiers vector hash struct range
 %type <val> list exprs exprs_opt expr n_exprs r_exprs n_expr n_exprs_opt
 %type <val> out_clauses out_clauses_opt out_clause
 %type <val> repeat_clause repeat_parts_opt o_line
@@ -737,6 +737,16 @@ struct : HASH_S list            { if (unquotes_occur($2, 0))
                                     $$ = rlcp(strct, num($1)); } }
        ;
 
+range : HASH_R list             { if (length($2) != two)
+                                    yyerr("range literal needs two elements");
+
+                                  if (unquotes_occur($2, 0))
+                                    $$ = rlcp(cons(rcons_s, $2), num($1));
+                                  else
+                                  { val range = rcons(first($2), second($2));
+                                    $$ = rlcp(range, num($1)); } }
+       ;
+
 list : '(' n_exprs ')'          { $$ = rl($2, num($1)); }
      | '(' ')'                  { $$ = nil; }
      | '(' LAMBDOT n_expr ')'   { $$ = $3; }
@@ -818,6 +828,7 @@ n_expr : SYMTOK                 { $$ = symhlpr($1, t); }
        | vector                 { $$ = $1; }
        | hash                   { $$ = $1; }
        | struct                 { $$ = $1; }
+       | range                  { $$ = $1; }
        | lisp_regex             { $$ = $1; }
        | chrlit                 { $$ = $1; }
        | strlit                 { $$ = $1; }
@@ -833,7 +844,7 @@ n_expr : SYMTOK                 { $$ = symhlpr($1, t); }
        | SPLICE n_expr          { $$ = rl(rlcp(list(sys_splice_s, $2, nao), $2),
                                           num(parser->lineno)); }
        | n_expr DOTDOT n_expr   { uses_or2;
-                                  $$ = rlcp(list(cons_s, $1, $3, nao),
+                                  $$ = rlcp(list(rcons_s, $1, $3, nao),
                                             or2($1, $3)); }
        | n_expr '.' n_expr      { uses_or2;
                                   if (consp($3) && car($3) == qref_s) {