🐐 DECIMATIO

centvrion/ast_nodes.py

@@ -957,6 +957,16 @@ class BuiltIn(Node):
           raise CentvrionError("SEMEN requires an integer seed")
         random.seed(seed)
         return vtable, ValNul()
+      case "DECIMATIO":
+        if "FORS" not in vtable["#modules"]:
+          raise CentvrionError("Cannot use 'DECIMATIO' without module 'FORS'")
+        if not isinstance(params[0], ValList):
+          raise CentvrionError("DECIMATIO requires an array")
+        arr = list(params[0].value())
+        to_remove = len(arr) // 10
+        for _ in range(to_remove):
+          arr.pop(random.randint(0, len(arr) - 1))
+        return vtable, ValList(arr)
       case "LONGITVDO":
         if isinstance(params[0], (ValList, ValStr)):
           return vtable, ValInt(len(params[0].value()))

centvrion/compiler/emit_expr.py

@@ -186,6 +186,13 @@ def _emit_builtin(node, ctx):
       else:
         lines.append(f"CentValue {tmp} = cent_fortis_electionis({param_vars[0]});")
 
+    case "DECIMATIO":
+      if not ctx.has_module("FORS"):
+        lines.append('cent_runtime_error("FORS module required for DECIMATIO");')
+        lines.append(f"CentValue {tmp} = cent_null();")
+      else:
+        lines.append(f"CentValue {tmp} = cent_decimatio({param_vars[0]});")
+
     case "SEMEN":
       if not ctx.has_module("FORS"):
         lines.append('cent_runtime_error("FORS module required for SEMEN");')

centvrion/compiler/runtime/cent_runtime.c

@@ -533,6 +533,25 @@ CentValue cent_fortis_electionis(CentValue lst) {
   return lst.lval.items[rand() % lst.lval.len];
 }
 
+CentValue cent_decimatio(CentValue lst) {
+  if (lst.type != CENT_LIST)
+    cent_type_error("'DECIMATIO' requires a list");
+  int len = lst.lval.len;
+  /* Copy the list so we can remove in-place */
+  CentValue result = cent_list_new(len);
+  for (int i = 0; i < len; i++)
+    cent_list_push(&result, lst.lval.items[i]);
+  int to_remove = result.lval.len / 10;
+  for (int i = 0; i < to_remove; i++) {
+    int idx = rand() % result.lval.len;
+    /* Shift remaining elements left */
+    for (int j = idx; j < result.lval.len - 1; j++)
+      result.lval.items[j] = result.lval.items[j + 1];
+    result.lval.len--;
+  }
+  return result;
+}
+
 void cent_semen(CentValue seed) {
   if (seed.type != CENT_INT)
     cent_type_error("'SEMEN' requires an integer seed");

centvrion/compiler/runtime/cent_runtime.h

@@ -177,6 +177,7 @@ CentValue cent_avdi_numerus(void);                    /* AVDI_NVMERVS */
 CentValue cent_longitudo(CentValue v);                  /* LONGITVDO  */
 CentValue cent_fortis_numerus(CentValue lo, CentValue hi); /* FORTIS_NVMERVS */
 CentValue cent_fortis_electionis(CentValue lst);          /* FORTIS_ELECTIONIS */
+CentValue cent_decimatio(CentValue lst);                       /* DECIMATIO */
 void      cent_semen(CentValue seed);                          /* SEMEN */
 void      cent_everro(void);                                   /* EVERRO */
 

centvrion/lexer.py

@@ -39,6 +39,7 @@ keyword_tokens = [("KEYWORD_"+i, i) for i in [
 builtin_tokens = [("BUILTIN", i) for i in [
   "AVDI_NVMERVS",
   "AVDI",
+  "DECIMATIO",
   "DICE",
   "EVERRO",
   "FORTIS_NVMERVS",