Merge pull request #80 from olback/math-consts-context

Add math consts context

src/lib.rs

@@ -523,6 +523,7 @@ mod feature_serde;
 mod function;
 mod interface;
 mod operator;
+mod predefined;
 mod token;
 mod tree;
 mod value;

src/predefined/mod.rs

@@ -0,0 +1,37 @@
+/// Context with all f64::consts available by default.
+/// Alternatively, specifiy constants with `math_consts_context!(E, PI, TAU, ...)`
+/// Available constants can be found in the [`core::f64::consts module`](https://doc.rust-lang.org/nightly/core/f64/consts/index.html).
+#[macro_export]
+macro_rules! math_consts_context {
+    () => {
+        $crate::math_consts_context!(
+            PI,
+            TAU,
+            FRAC_PI_2,
+            FRAC_PI_3,
+            FRAC_PI_4,
+            FRAC_PI_6,
+            FRAC_PI_8,
+            FRAC_1_PI,
+            FRAC_2_PI,
+            FRAC_2_SQRT_PI,
+            SQRT_2,
+            FRAC_1_SQRT_2,
+            E,
+            LOG2_10,
+            LOG2_E,
+            LOG10_2,
+            LOG10_E,
+            LN_2,
+            LN_10
+        )
+    };
+    ($($name:ident),*) => {{
+        use $crate::ContextWithMutableVariables;
+        $crate::context_map! {
+            $(
+                stringify!($name) => core::f64::consts::$name,
+            )*
+        }
+    }};
+}