Fix function body literal mutation: make examples pass

Two bugs combined to break uber.fy and any function called more than once:

1. Scanner split identifiers at '_' boundaries (e.g. arr_sum → arr + _sum).
   Fixed by adding d != '_' to the token-splitting guard condition so
   underscores are treated as part of identifiers.

2. Dead keyword TT_ARR reserved the name 'arr' as a keyword token,
   preventing its use as a function parameter.  Removed TT_ARR from the
   enum, keyword table, and name table.

3. (Root cause of the assert failure) _var_assign stored the symbol for a
   newly declared variable pointing directly at the literal token from the
   function body token list.  incr/decr modify tokens in place via
   stack_top, so a loop like `my i = 0; while i < n { incr i; }` would
   corrupt the body's '0' literal — on the next call i starts at 10 instead
   of 0.  Fixed by allocating a fresh token_new_integer / token_new_dummy
   for TT_INTEGER and TT_DOUBLE initialisers so body literals are never
   mutated.  Arrays and strings retain reference semantics unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

9 files changed, 18 insertions, 9 deletions

diff --git a/docs/help.txt b/docs/help.txt
index 4c3ded3..204cbd3 100644
--- a/docs/help.txt
+++ b/docs/help.txt
@@ -1,4 +1,4 @@
-Fype Superalpha Build 9705
+Fype Superalpha Build 9720
 (c) Paul C. Buetow (2005 - 2008) <fype@dev.buetow.org>
 	-e	Executes given code string (see synopses)
 	-h	Prints this help
diff --git a/docs/stats.txt b/docs/stats.txt
index e4a2d10..09e90e9 100644
--- a/docs/stats.txt
+++ b/docs/stats.txt
@@ -1,6 +1,6 @@
 make[1]: Entering directory '/home/paul/git/fype'
 ===> Num of C source files		: 46
-===> Num of C source lines		:   8744 
+===> Num of C source lines		:   8753 
 ===> Num of Fype source examples	: 19
 ===> Num of Fype source lines		:   883 
 make[1]: Leaving directory '/home/paul/git/fype'
diff --git a/docs/version.txt b/docs/version.txt
index baab03e..646d854 100644
--- a/docs/version.txt
+++ b/docs/version.txt
@@ -1 +1 @@
-Fype Superalpha Build 9705
+Fype Superalpha Build 9720
diff --git a/fype b/fype
index edcafc8..d6e0e8f 100755
--- a/fype
+++ b/fype
diff --git a/src/build.h b/src/build.h
index cd6ed73..7e13941 100644
--- a/src/build.h
+++ b/src/build.h
@@ -36,7 +36,7 @@
 #ifndef BUILD_H
 #define BUILD_H
 
-#define BUILDNR 9709
+#define BUILDNR 9731
 #define OS_LINUX
 
 #endif
diff --git a/src/core/interpret.c b/src/core/interpret.c
index 7fc9334..38464f8 100644
--- a/src/core/interpret.c
+++ b/src/core/interpret.c
@@ -267,7 +267,19 @@ _var_assign(Interpret *p_interpret) {
                p_interpret->p_stack = p_stack;
 
                p_token = stack_top(p_interpret->p_stack);
-               Symbol *p_symbol = symbol_new(SYM_VARIABLE, p_token);
+               /* For scalar types, own a fresh token so that in-place
+                * mutations (incr/decr) don't corrupt the function body's
+                * literal tokens across repeated calls. Arrays and strings
+                * keep reference semantics as-is. */
+               Token *p_own = p_token;
+               if (token_get_tt(p_token) == TT_INTEGER) {
+                  p_own = token_new_integer(token_get_ival(p_token));
+               } else if (token_get_tt(p_token) == TT_DOUBLE) {
+                  p_own = token_new_dummy();
+                  token_set_tt(p_own, TT_DOUBLE);
+                  token_set_dval(p_own, token_get_dval(p_token));
+               }
+               Symbol *p_symbol = symbol_new(SYM_VARIABLE, p_own);
                scope_newset(p_interpret->p_scope, c_name, p_symbol);
             } else {
                return (0);
diff --git a/src/core/scanner.c b/src/core/scanner.c
index 87fc624..7eecb01 100644
--- a/src/core/scanner.c
+++ b/src/core/scanner.c
@@ -287,7 +287,7 @@ scanner_run(List *p_list_token, Tupel *p_tupel_argv,
                _add_semicolon_to_list(p_scanner);
 
             char d = c_token[i_token_len-1];
-            if ((!isalpha(d) && !isdigit(d) /*&& d != '-'*/) &&
+            if ((!isalpha(d) && !isdigit(d) && d != '_' /*&& d != '-'*/) &&
                   (isalpha(c) || isdigit(c))) {
 
                scanner_add_token(p_scanner, &c_token, &i_token_len,
diff --git a/src/core/token.c b/src/core/token.c
index f7cc745..b31bed9 100644
--- a/src/core/token.c
+++ b/src/core/token.c
@@ -61,7 +61,6 @@ get_tt(char *c_token) {
    CHECK("proc") TT_PROC;
    CHECK("fun") TT_FUNC;
    CHECK("my") TT_MY;
-   CHECK("arr") TT_ARR;
    CHECK("!") TT_NOT;
    CHECK("!=") TT_NEQ;
    CHECK("=~") TT_RE;
@@ -127,7 +126,6 @@ tt_get_name(TokenType tt_cur) {
       CASE(TT_PROC,"TT_PROC")
       CASE(TT_FUNC,"TT_FUNC")
       CASE(TT_MY,"TT_MY")
-      CASE(TT_ARR,"TT_ARR")
       CASE(TT_WHILE,"TT_WHILE")
       CASE(TT_UNTIL,"TT_UNTIL")
       CASE(TT_NEXT,"TT_NEXT")
diff --git a/src/core/token.h b/src/core/token.h
index 497dc78..b7e77a9 100644
--- a/src/core/token.h
+++ b/src/core/token.h
@@ -101,7 +101,6 @@ typedef enum {
    TT_PROC,
    TT_FUNC,
    TT_MY,
-   TT_ARR,
    TT_WHILE,
    TT_UNTIL,
    TT_NEXT,