new function: random()

random() returns a random number between 0 and 1

Cargo.toml

@@ -26,6 +26,7 @@ path = "src/lib.rs"
 regex = { version = "1.5.5", optional = true}
 serde = { version = "1.0.133", optional = true}
 serde_derive = { version = "1.0.133", optional = true}
+rand = { version = "0.8", optional = true}
 
 [features]
 serde_support = ["serde", "serde_derive"]
@@ -33,5 +34,5 @@ regex_support = ["regex"]
 
 [dev-dependencies]
 ron = "0.7.0"
-rand = "0.8.4"
+rand = "0.8.5"
 rand_pcg = "0.3.1"

README.md

@@ -380,6 +380,7 @@ This crate offers a set of builtin functions.
 | `bitnot`             | 1               | Int                    | Computes the bitwise not of the given integer |
 | `shl`                | 2               | Int                    | Computes the given integer bitwise shifted left by the other given integer |
 | `shr`                | 2               | Int                    | Computes the given integer bitwise shifted right by the other given integer |
+| `random`             | 0               | Empty                  | Return a random float between 0 and 1. Requires the `rand` feature flag. |
 
 The `min` and `max` functions can deal with a mixture of integer and floating point arguments.
 If the maximum or minimum is an integer, then an integer is returned.

src/function/builtin.rs

@@ -185,6 +185,11 @@ pub fn builtin_function(identifier: &str) -> Option<Function> {
         "str::from" => Some(Function::new(|argument| {
             Ok(Value::String(argument.to_string()))
         })),
+        #[cfg(feature = "rand")]
+        "random" => Some(Function::new(|argument| {
+            argument.as_empty()?;
+            Ok(Value::Float(rand::random()))
+        })),
         // Bitwise operators
         "bitand" => int_function!(bitand, 2),
         "bitor" => int_function!(bitor, 2),

src/lib.rs

@@ -363,6 +363,7 @@
 //! | `bitnot`             | 1               | Int                    | Computes the bitwise not of the given integer |
 //! | `shl`                | 2               | Int                    | Computes the given integer bitwise shifted left by the other given integer |
 //! | `shr`                | 2               | Int                    | Computes the given integer bitwise shifted right by the other given integer |
+//! | `random`             | 0               | Empty                  | Return a random float between 0 and 1. Requires the `rand` feature flag. |
 //!
 //! The `min` and `max` functions can deal with a mixture of integer and floating point arguments.
 //! If the maximum or minimum is an integer, then an integer is returned.

tests/rand.rs

@@ -0,0 +1,22 @@
+#![cfg(feature = "rand")]
+
+use evalexpr::*;
+
+fn assert_expr(expr: &str) {
+    assert_eq!(eval(expr), Ok(Value::Boolean(true)))
+}
+
+#[test]
+fn test_random() {
+    for _ in 0..100 {
+        assert_expr("random() != random()");
+        assert_expr("0 <= random()");
+        assert_expr("random() <= 1");
+    }
+}
+
+#[test]
+fn test_random_errors() {
+    assert!(eval("random(9)").is_err());
+    assert!(eval("random(\"a\", \"b\")").is_err());
+}