added blockpredicate argument support

docs/scarpet/api/Overview.md

@@ -206,6 +206,20 @@ Here is a list of built-in types, with their return value formats, as well as a
   * `'pos'`: block position as a triple of coordinates. Customized with `'loaded'`, if true requiring the position 
   to be loaded.
   * `'block'`: a valid block state wrapped in a block value (including block properties and data)
+  * `'blockpredicate`': returns a 4-tuple indicating conditions of a block to match: block name, block tag,
+  map of required state properties, and tag to match. Either block name or block tag are `null` but not both.
+  Property map is always specified, but its empty for no conditions, and matching nbt tag can be `null` indicating
+  no requirements. Technically the 'all-matching' predicate would be `[null, null, {}, null]`, but 
+  block name or block tag is always specified. One can use the following routine to match a block agains this predicate:
+  ```
+    block_to_match = block(x,y,z);
+    [block_name, block_tag, properties, nbt_tag] = block_predicate;
+   
+    (block_name == null || block_name == block_to_match) &&
+    (block_tag == null || block_tags(block_to_match, block_tag)) &&
+    all(properties, block_state(block_to_match, _) == properties:_) &&
+    (!tag || tag_matches(block_data(block_to_match), tag))
+  ```
   * `'teamcolor'`: name of a team, and an integer color value of one of 16 valid team colors.
   * `'columnpos'`: a pair of x and z coordinates.
   * `'dimension'`: string representing a valid dimension in the world.

src/main/resources/assets/carpet/scripts/draw_beta.sc

@@ -20,7 +20,7 @@ __config() -> {
     'arguments'->{
         'center'->{'type'->'pos', 'loaded'->'true'},
         'radius'->{'type'->'int', 'suggest'->[], 'min'->0},//to avoid default suggestions
-        'replacement'->{'type'->'block'},
+        'replacement'->{'type'->'blockpredicate'},
         'height'->{'type'->'int', 'suggest'->[],'min'->0},
         'orientation'->{'type'->'term', 'suggest'->['x','y','z']},
         'pointing'->{'type'->'term','suggest'->['up','down']},
@@ -32,9 +32,20 @@ __config() -> {
 
 //"Boilerplate" code
 
+_block_matches(existing, block_predicate) ->
+(
+    [name, block_tag, properties, nbt] = block_predicate;
+
+    (name == null || name == existing) &&
+    (block_tag == null || block_tags(existing, block_tag)) &&
+    all(properties, block_state(existing, _) == properties:_) &&
+    (!tag || tag_matches(block_data(existing), tag))
+);
+
 set_block(x, y, z, block, replacement)-> (
-    if(block != block(x, y, z),
+    existing = block(x, y, z);
-        without_updates( if (set([x, y, z],block),
+    if(block != existing && (replacement && _block_matches(existing, replacement) ),
+        without_updates( if (set(existing,block),
             global_affected += [x, y, z];
         ));
     );