A string interpolation syntax that I don't hate. Also tests.

You can interpolate values into strings using \(this syntax), e.g.

    "best \("str" + "ing") ever"

lexer.l

@@ -61,45 +61,31 @@
 }
 
 
-\"(\\.|[^\\\"])*\" |
 -?[0-9.]+([eE][+-]?[0-9]+)? { 
    yylval->literal = jv_parse_sized(yytext, yyleng); return LITERAL; 
 }
 
-\"(\\.|[^\\\"])* { 
-  yylval->literal = jv_invalid_with_msg(jv_string("Unterminated string"));
-  return LITERAL;
-}
-
-"@(" {
+"\"" {
   yy_push_state(IN_QQSTRING, yyscanner);
   return QQSTRING_START;
 }
 
 <IN_QQSTRING>{
-  "%(" {
+  "\\(" {
     return enter(QQSTRING_INTERP_START, YY_START, yyscanner);
   }
-  "%"[^(] {
-    return INVALID_CHARACTER;
-  }
-  ")" {
+  "\"" {
     yy_pop_state(yyscanner);
     return QQSTRING_END;
   }
-  "\\"[)%] {
-    char text[2] = {yytext[1], 0};
-    yylval->literal = jv_string(text);
-    return QQSTRING_TEXT;
-  }
-  (\\[^u)%]|\\u[a-zA-Z0-9]{0,4})+ {
+  (\\[^u(]|\\u[a-zA-Z0-9]{0,4})+ {
     /* pass escapes to the json parser */
     jv escapes = jv_string_fmt("\"%.*s\"", yyleng, yytext);
     yylval->literal = jv_parse_sized(jv_string_value(escapes), jv_string_length(jv_copy(escapes)));
     jv_free(escapes);
     return QQSTRING_TEXT;
   }
-  [^\\)%]+ {
+  [^\\\"]+ {
     yylval->literal = jv_string_sized(yytext, yyleng);
     return QQSTRING_TEXT;
   }