1 files changed, 60 insertions, 0 deletions
diff --git a/src/expression_function.rs b/src/expression_function.rs
new file mode 100644
index 0000000..35eba5f
--- /dev/null
+++ b/src/expression_function.rs
@@ -0,0 +1,60 @@
+use std::{collections::HashMap, iter::zip};
+
+use crate::{
+    commonsense_functions, commonsense_operations, functions,
+    complex::Complex,
+    context::Context,
+    expression::Expression,
+    operation::Operation,
+    function::{Function, FunctionArgument}
+};
+
+pub struct ExpressionFunction {
+    expr: Expression,
+    name: String,
+    args: Vec<String>,
+}
+
+impl ExpressionFunction {
+    pub fn from_string(str: String) -> Self {
+        let str = str.replace(' ', "");
+        let (lhs, expr) = str.split_once('=').unwrap();
+        let (name, a) = lhs.split_once('(').unwrap();
+        let args: Vec<String> = a[0..a.len() - 1]
+            .split(',')
+            .into_iter()
+            .map(|s| s.to_string())
+            .collect();
+        Self {
+            expr: Expression::from_string(expr),
+            name: name.to_string(),
+            args,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+}
+
+impl Function for ExpressionFunction {
+    fn eval(&self, args: FunctionArgument) -> Result<Complex, String> {
+        if args.len() == self.args.len() {
+            let mut vars = HashMap::new();
+            for (n, v) in zip(self.args.iter(), args.data().iter()) {
+                vars.insert(n.to_string(), v.clone());
+            }
+            let ctx = Context::new()
+                .with_variables(vars)
+                .with_functions(commonsense_functions! {})
+                .with_operations(commonsense_operations! {});
+            self.expr.evaluate(&ctx)
+        } else {
+            Err(format!(
+                "{} takes {} parameters",
+                self.name,
+                self.args.len()
+            ))
+        }
+    }
+}