support named characters

src/port.c

@@ -33,7 +33,17 @@ write(pic_state *pic, pic_value obj)
     printf("%s", pic_symbol_name(pic, pic_sym(obj)));
     break;
   case PIC_TT_CHAR:
-    printf("#\\%c", pic_char(obj));
+    switch (pic_char(obj)) {
+    default: printf("#\\%c", pic_char(obj)); break;
+    case '\a': printf("#\\alarm"); break;
+    case '\b': printf("#\\backspace"); break;
+    case 0x7f: printf("#\\delete"); break;
+    case 0x1b: printf("#\\escape"); break;
+    case '\n': printf("#\\newline"); break;
+    case '\r': printf("#\\return"); break;
+    case ' ': printf("#\\space"); break;
+    case '\t': printf("#\\tab"); break;
+    }
     break;
   case PIC_TT_FLOAT:
     printf("%f", pic_float(obj));

src/scan.l

@@ -30,6 +30,9 @@ uinteger	{digit}+
 sign		[+-]?
 infnan		"+inf.0"|"-inf.0"|"+nan.0"|"-nan.0"
 
+  /* char */
+%x CHAR
+
   /* string */
 %x STRING
 
@@ -84,10 +87,19 @@ infnan		"+inf.0"|"-inf.0"|"+nan.0"|"-nan.0"
 			}
 }
 
-#\\.		{
-  yylvalp->c = yytext[2];
-  return tCHAR;
+#\\		{
+  BEGIN(CHAR);
 }
+<CHAR>alarm	{ yylvalp->c = '\a'; BEGIN(INITIAL); return tCHAR; }
+<CHAR>backspace	{ yylvalp->c = '\b'; BEGIN(INITIAL); return tCHAR; }
+<CHAR>delete	{ yylvalp->c = 0x7f; BEGIN(INITIAL); return tCHAR; }
+<CHAR>escape	{ yylvalp->c = '\e'; BEGIN(INITIAL); return tCHAR; }
+<CHAR>newline	{ yylvalp->c = '\n'; BEGIN(INITIAL); return tCHAR; }
+<CHAR>null	{ yylvalp->c = '\0'; BEGIN(INITIAL); return tCHAR; }
+<CHAR>return	{ yylvalp->c = '\r'; BEGIN(INITIAL); return tCHAR; }
+<CHAR>space	{ yylvalp->c = ' '; BEGIN(INITIAL); return tCHAR; }
+<CHAR>tab	{ yylvalp->c = '\t'; BEGIN(INITIAL); return tCHAR; }
+<CHAR>.		{ yylvalp->c = yytext[0]; BEGIN(INITIAL); return tCHAR; }
 
 "#u8("		{
   BEGIN(BYTEVECTOR);