From b31c9587bc598ab038d70d1cf4f6daec8c16d989 Mon Sep 17 00:00:00 2001
From: ConnorSkees <39542938+ConnorSkees@users.noreply.github.com>
Date: Fri, 14 Feb 2020 10:10:51 -0500
Subject: [PATCH] Implement builtin function `length()`

---
 src/builtin/list.rs | 14 ++++++++++++++
 src/builtin/mod.rs  |  1 +
 2 files changed, 15 insertions(+)

diff --git a/src/builtin/list.rs b/src/builtin/list.rs
index 8b13789..58acc76 100644
--- a/src/builtin/list.rs
+++ b/src/builtin/list.rs
@@ -1 +1,15 @@
+use std::collections::BTreeMap;
 
+use super::Builtin;
+use crate::units::Unit;
+use crate::value::{Number, Value};
+
+pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
+    decl!(f "length", |args, _| {
+        let len = match arg!(args, 0, "list").eval() {
+            Value::List(v, _) => Number::from(v.len()),
+            _ => Number::from(1)
+        };
+        Some(Value::Dimension(len, Unit::None))
+    });
+}
diff --git a/src/builtin/mod.rs b/src/builtin/mod.rs
index eed9302..3cb388f 100644
--- a/src/builtin/mod.rs
+++ b/src/builtin/mod.rs
@@ -22,6 +22,7 @@ lazy_static! {
     pub(crate) static ref GLOBAL_FUNCTIONS: BTreeMap<String, Builtin> = {
         let mut m = BTreeMap::new();
         color::register(&mut m);
+        list::register(&mut m);
         math::register(&mut m);
         meta::register(&mut m);
         string::register(&mut m);