diff --git a/src/token/function.rs b/src/token/function.rs
index 20e2c0a..55b9428 100644
--- a/src/token/function.rs
+++ b/src/token/function.rs
@@ -74,6 +74,7 @@ pub mod built_in_functions {
     pub const TAN: Function = xprs_fn!("tan", f64::tan, 1);
     pub const TANH: Function = xprs_fn!("tanh", f64::tanh, 1);
     pub const ATAN: Function = xprs_fn!("atan", f64::atan, 1);
+    pub const ATAN2: Function = xprs_fn!("atan2", f64::atan2, 2);
     pub const ATANH: Function = xprs_fn!("atanh", f64::atanh, 1);
     // log
     pub const LN: Function = xprs_fn!("ln", f64::ln, 1);
@@ -94,4 +95,13 @@ pub mod built_in_functions {
     pub const MEAN: Function = xprs_fn!("mean", |args| {
         args.iter().sum::<f64>() / args.len() as f64
     });
+    pub const INVERT: Function = xprs_fn!("invert", f64::recip, 1);
+    pub const MIN: Function = xprs_fn!("min", |args| {
+        args.iter().fold(f64::INFINITY, |acc, &x| acc.min(x))
+    });
+    pub const MAX: Function = xprs_fn!("max", |args| {
+        args.iter().fold(f64::NEG_INFINITY, |acc, &x| acc.max(x))
+    });
+    pub const HYPOT: Function = xprs_fn!("hypot", f64::hypot, 2);
+    pub const FRACT: Function = xprs_fn!("fract", f64::fract, 1);
 }
diff --git a/src/token/identifier.rs b/src/token/identifier.rs
index f55df57..e29c375 100644
--- a/src/token/identifier.rs
+++ b/src/token/identifier.rs
@@ -31,6 +31,7 @@ impl<'a> From<&'a str> for Identifier<'a> {
             "tan" => built_in_functions::TAN.into(),
             "tanh" => built_in_functions::TANH.into(),
             "atan" => built_in_functions::ATAN.into(),
+            "atan2" => built_in_functions::ATAN2.into(),
             "atanh" => built_in_functions::ATANH.into(),
             // log
             "ln" => built_in_functions::LN.into(),
@@ -48,6 +49,11 @@ impl<'a> From<&'a str> for Identifier<'a> {
             "trunc" => built_in_functions::TRUNC.into(),
             "sum" => built_in_functions::SUM.into(),
             "mean" => built_in_functions::MEAN.into(),
+            "invert" => built_in_functions::INVERT.into(),
+            "min" => built_in_functions::MIN.into(),
+            "max" => built_in_functions::MAX.into(),
+            "hypot" => built_in_functions::HYPOT.into(),
+            "fract" => built_in_functions::FRACT.into(),
             /* Variables */
             _ => Identifier::Variable(value),
         }