(Global) variables

[plepe]

It would be great if it would be possible to use (global) variables. Similar to less these could be prefixed by '@'. So that a variable gets global, it should first be used in global space. Example (similar to #77, but rather extending it):

/* initialize variable @list with an empty list, making it global */
@list: list();

/* process all peaks ordered by elevation downward */
node[natural=peak]:order-numerical-desc(ele) {
  /* to @list append the name of the current map feature */
  @list: append(@list, tag("name"));
}

/* print current @list to stderr, which should be the names of all peaks 
 * in current bounding box, ordered by elevation downward */
debug(@list);

The following things need to be implemented:

• variables, which are names prepended by @
• check reserved names
• statements in global space, even without destination where the result should go to (like the debug() in the last row).
• use variables inside of eval statements
• delay execution of map features if rules after a global statement use/modify a global variable

How to do?

• save block of global statements as if they are a normal rule
• compile as a function similar to check_X, execute from main loop with list of other objects