1 files changed, 15 insertions, 0 deletions

diff --git a/src/lisp/prelude.rs b/src/lisp/prelude.rs
index 336dbaf..aebff98 100644
--- a/src/lisp/prelude.rs
+++ b/src/lisp/prelude.rs
@@ -1,6 +1,7 @@
 use crate::{
     bitmap::MapPoint,
     brush::Brush,
+    guide::Guide,
     lisp::{
         error::{EvalError, LispError},
         expr::{Arity, LispExpr},
@@ -413,5 +414,19 @@ pub fn new_env() -> Result<Environment, LispError> {
         return Ok(LispExpr::Unit);
     });
 
+    primitive!(env, Arity::Exact(2), "add-guide!", |args, app| {
+        match args {
+            [axis, LispExpr::Number(LispNumber::Integer(offset))] => {
+                let guide = Guide {
+                    axis: axis.try_into()?,
+                    offset: *offset as u32,
+                };
+                app.guides.insert(guide, true);
+                return Ok(LispExpr::Unit);
+            }
+            _ => return Err(EvalError::TypeMismatch.into()),
+        }
+    });
+
     Ok(env)
 }