implement list-length

1 files changed, 8 insertions, 0 deletions

diff --git a/interpreter.py b/interpreter.py
index 03b5c00..c491150 100644
--- a/interpreter.py
+++ b/interpreter.py
@@ -357,6 +357,14 @@ GLOBALS.register("strip", Builtin(interpretStrip, 1))
 #  - string->int and string->float
 #  - split a string by a given field
 #  - get the length of a list
+def interpretListLength(symbol, args, env):
+    ev = evaluate(args[0], env)
+    if not isinstance(ev, List):
+        raise Exception("'first' expects a List")
+    return len(ev.args)
+
+GLOBALS.register("list-length", Builtin(interpretListLength, 1))
+    
 #  - first/rest of list
 def interpretFirst(symbol, args, env):
     ev = evaluate(args[0], env)