diff --git a/src/function/builtin.rs b/src/function/builtin.rs
index fa776d4..5ea0aac 100644
--- a/src/function/builtin.rs
+++ b/src/function/builtin.rs
@@ -6,8 +6,49 @@ use crate::{
     EvalexprError, Function, Value, ValueType,
 };
 
+macro_rules! simple_math {
+    ($func:ident) => {
+        Some(Function::new(|argument| {
+            let num = argument.as_number()?;
+            Ok(Value::Float(num.$func()))
+        }))
+    };
+}
+
 pub fn builtin_function(identifier: &str) -> Option<Function> {
     match identifier {
+        // Log
+        "ln" => simple_math!(ln),
+        "log" => Some(Function::new(|argument| {
+            let tuple = argument.as_fixed_len_tuple(2)?;
+            let (a, b) = (tuple[0].as_number()?, tuple[1].as_number()?);
+            Ok(Value::Float(a.log(b)))
+        })),
+        "log2" => simple_math!(log2),
+        "log10" => simple_math!(log10),
+        // Cos
+        "cos" => simple_math!(cos),
+        "acos" => simple_math!(acos),
+        "cosh" => simple_math!(cosh),
+        "acosh" => simple_math!(acosh),
+        // Sin
+        "sin" => simple_math!(sin),
+        "asin" => simple_math!(asin),
+        "sinh" => simple_math!(sinh),
+        "asinh" => simple_math!(asinh),
+        // Tan
+        "tan" => simple_math!(tan),
+        "atan" => simple_math!(atan),
+        "tanh" => simple_math!(tanh),
+        "atanh" => simple_math!(atanh),
+        // Root
+        "sqrt" => simple_math!(sqrt),
+        "cbrt" => simple_math!(cbrt),
+        // Rounding
+        "floor" => simple_math!(floor),
+        "round" => simple_math!(round),
+        "ceil" => simple_math!(ceil),
+        // Other
         "min" => Some(Function::new(|argument| {
             let arguments = argument.as_tuple()?;
             let mut min_int = IntType::max_value();
@@ -52,7 +93,6 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
                 Ok(Value::Float(max_float))
             }
         })),
-
         "len" => Some(Function::new(|argument| {
             if let Ok(subject) = argument.as_string() {
                 Ok(Value::from(subject.len() as i64))
@@ -65,8 +105,7 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
                 ))
             }
         })),
-
-        // string functions
+        // String functions
         #[cfg(feature = "regex_support")]
         "str::regex_matches" => Some(Function::new(|argument| {
             let arguments = argument.as_tuple()?;
@@ -110,6 +149,9 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
             let subject = argument.as_string()?;
             Ok(Value::from(subject.trim()))
         })),
+        "str::from" => Some(Function::new(|argument| {
+            Ok(Value::String(argument.to_string()))
+        })),
         _ => None,
     }
 }
diff --git a/tests/integration.rs b/tests/integration.rs
index 1bdede7..972c0ac 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -271,10 +271,44 @@ fn test_n_ary_functions() {
 
 #[test]
 fn test_builtin_functions() {
+    // Log
+    assert_eq!(eval("ln(2.718281828459045)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("log(9, 9)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("log2(2)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("log10(10)"), Ok(Value::Float(1.0)));
+    // Cos
+    assert_eq!(eval("cos(0)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("acos(1)"), Ok(Value::Float(0.0)));
+    assert_eq!(eval("cosh(0)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("acosh(1)"), Ok(Value::Float(0.0)));
+    // Sin
+    assert_eq!(eval("sin(0)"), Ok(Value::Float(0.0)));
+    assert_eq!(eval("asin(0)"), Ok(Value::Float(0.0)));
+    assert_eq!(eval("sinh(0)"), Ok(Value::Float(0.0)));
+    assert_eq!(eval("asinh(0)"), Ok(Value::Float(0.0)));
+    // Tan
+    assert_eq!(eval("tan(0)"), Ok(Value::Float(0.0)));
+    assert_eq!(eval("atan(0)"), Ok(Value::Float(0.0)));
+    assert_eq!(eval("tanh(0)"), Ok(Value::Float(0.0)));
+    assert_eq!(eval("atanh(0)"), Ok(Value::Float(0.0)));
+    // Root
+    assert_eq!(eval("sqrt(25)"), Ok(Value::Float(5.0)));
+    assert_eq!(eval("cbrt(8)"), Ok(Value::Float(2.0)));
+    // Rounding
+    assert_eq!(eval("floor(1.1)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("floor(1.9)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("round(1.1)"), Ok(Value::Float(1.0)));
+    assert_eq!(eval("round(1.5)"), Ok(Value::Float(2.0)));
+    assert_eq!(eval("round(2.5)"), Ok(Value::Float(3.0)));
+    assert_eq!(eval("round(1.9)"), Ok(Value::Float(2.0)));
+    assert_eq!(eval("ceil(1.1)"), Ok(Value::Float(2.0)));
+    assert_eq!(eval("ceil(1.9)"), Ok(Value::Float(2.0)));
+    // Other
     assert_eq!(eval("min(4.0, 3)"), Ok(Value::Int(3)));
     assert_eq!(eval("max(4.0, 3)"), Ok(Value::Float(4.0)));
     assert_eq!(eval("len(\"foobar\")"), Ok(Value::Int(6)));
     assert_eq!(eval("len(\"a\", \"b\")"), Ok(Value::Int(2)));
+    // String
     assert_eq!(
         eval("str::to_lowercase(\"FOOBAR\")"),
         Ok(Value::from("foobar"))
@@ -287,6 +321,12 @@ fn test_builtin_functions() {
         eval("str::trim(\"  foo  bar \")"),
         Ok(Value::from("foo  bar"))
     );
+    assert_eq!(eval("str::from(\"a\")"), Ok(Value::String(String::from("\"a\""))));
+    assert_eq!(eval("str::from(1.0)"), Ok(Value::String(String::from("1"))));
+    assert_eq!(eval("str::from(1)"), Ok(Value::String(String::from("1"))));
+    assert_eq!(eval("str::from(true)"), Ok(Value::String(String::from("true"))));
+    assert_eq!(eval("str::from(1, 2, 3)"), Ok(Value::String(String::from("(1, 2, 3)"))));
+    assert_eq!(eval("str::from()"), Ok(Value::String(String::from("()"))));
 }
 
 #[test]