hints

src/egui_app.rs

@@ -1,6 +1,6 @@
 use crate::function::{FunctionEntry, Riemann, DEFAULT_FUNCTION_ENTRY};
 use crate::misc::{dyn_mut_iter, option_vec_printer, JsonFileOutput, SerdeValueHelper};
-use crate::parsing::{process_func_str, test_func};
+use crate::parsing::{generate_hint, process_func_str, test_func};
 
 use crate::consts::*;
 use eframe::{egui, epi};
@@ -446,8 +446,6 @@ impl MathApp {
 
 				let functions_len = self.functions.len();
 				let mut remove_i: Option<usize> = None;
-
-				let mut gave_hint: bool = false;
 				for (i, function) in self.functions.iter_mut().enumerate() {
 					let mut integral_enabled = function.integral;
 					let mut derivative_enabled = function.derivative;
@@ -493,13 +491,11 @@ impl MathApp {
 							.clicked();
 
 						// Contains the function string in a text box that the user can edit
-						TextEdit::singleline(&mut self.func_strs[i])
-							.hint_text(if gave_hint { "" } else { "x^2" })
-							.ui(ui);
+						let hint = generate_hint(&self.func_strs[i]);
 
-						if self.func_strs[i].is_empty() {
-							gave_hint = true;
-						}
+						TextEdit::singleline(&mut self.func_strs[i])
+							.hint_text(hint, true)
+							.ui(ui);
 					});
 
 					let proc_func_str = process_func_str(&self.func_strs[i]);

src/parsing.rs

@@ -204,6 +204,23 @@ pub fn test_func(function_string: &str) -> Option<String> {
 	}
 }
 
+pub fn generate_hint(input: &str) -> String {
+	if input.is_empty() {
+		return "x^2".to_owned();
+	}
+
+	let chars: Vec<char> = input.chars().collect();
+
+	let open_parens = chars.iter().filter(|c| **c == '(').count();
+	let closed_parents = chars.iter().filter(|c| **c == ')').count();
+
+	if open_parens > closed_parents {
+		return ")".to_owned();
+	}
+
+	String::new()
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;