1 files changed, 60 insertions, 0 deletions
diff --git a/src/math/expression_function.rs b/src/math/expression_function.rs
new file mode 100644
index 0000000..20f4816
--- /dev/null
+++ b/src/math/expression_function.rs
@@ -0,0 +1,60 @@
+use std::iter::zip;
+use std::sync::Arc;
+
+use crate::math::{
+    complex::Complex,
+    context::Context,
+    expression::Expression,
+    function::{Function, FunctionArgument, EmptyFunction}
+};
+
+#[derive(Default)]
+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(',')
+            .map(|s| s.to_string())
+            .collect();
+        Self {
+            expr: Expression::from_string(expr),
+            name: name.to_string(),
+            args,
+        }
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn content(&self) -> &str {
+        &self.expr.content()
+    }
+}
+
+impl Function for ExpressionFunction {
+    fn eval(&self, args: FunctionArgument, ctx: &Context) -> Result<Complex, String> {
+        if args.len() == self.args.len() {
+            let mut nctx = ctx.clone();
+            for (n, v) in zip(self.args.iter(), args.data().iter()) {
+                nctx.set_variable(n, *v)
+            }
+            nctx.set_function(self.name(), Arc::new(EmptyFunction {}));
+            self.expr.evaluate(&nctx)
+        } else {
+            Err(format!(
+                "{} takes {} parameters",
+                self.name,
+                self.args.len()
+            ))
+        }
+    }
+}