basic filter and error display

src/bin/ccc/mod.rs

@@ -129,6 +129,13 @@ fn main() {
 
     debug!("exporssion: {}", expr);
     let r = Calculator::oneshot(expr);
-    println!("{}", r.unwrap());
+    match r {
+        Ok(r) => {
+            println!("{r}");
+        }
+        Err(err) => {
+            error!("Could not compute: {err}");
+        }
+    }
 }
 ////////////////////////////////////////////////////////////////////////////////////////////////////

src/math/calculator/base.rs

@@ -72,7 +72,7 @@ pub enum Function {
 #[non_exhaustive]
 #[derive(Debug)]
 pub enum Error {
-    SyntaxError
+    SyntaxError(String)
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -120,6 +120,17 @@ impl<T: num_traits::PrimInt> From<T> for NumVal where
         }
     }
 }
+////////////////////////////////////////////////////////////////////////////////////////////////////
+/// Display Errors with a nice little reason
+impl Display for Error {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::SyntaxError(reason) => {
+                write!(f, "Syntax Error: {}", reason)
+            }
+        }
+    }
+}
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 impl<T: PrimInt> From<T> for Value where

src/math/calculator/mod.rs

@@ -40,6 +40,7 @@ use crate::logger::{trace, debug, info, warn, error};
 /// This struct does not do anything at the moment, but aims to be the target for high level
 /// control. Instead of using the [`Calculator`], you could just use the [`Term`] struct for
 /// lower level control.
+#[derive(Debug)]
 pub struct Calculator;
 
 //// IMPLEMENTATION ////////////////////////////////////////////////////////////////////////////////
@@ -65,8 +66,9 @@ impl Calculator {
         t.prepare()?;
         t.process()?;
         if t.result.is_none() {
-            error!("Term was processed but no result was assigned.");
-            return Err(Error::SyntaxError)
+            let reason = format!("Term was processed but no result was assigned.");
+            // FIXME: unfitting error type
+            return Err(Error::SyntaxError(reason))
         }
         return t.result.unwrap()
     }

src/math/calculator/term.rs

@@ -58,6 +58,8 @@ enum Token {
 pub struct Term {
     /// the original expression to calculate
     pub original: String,
+    /// the filtered text of the expression, only with relevant information
+    pub text: String,
     /// the calculated result, may be of diffrent types, see [`crate::math::calculator::result`].
     pub result: Option<Result<Value>>,
     /////////////////////////////////////
@@ -76,6 +78,7 @@ impl Term {
         return Ok(
             Term {
                 original: orig,
+                text: String::new(), // will be initialized in `prepare()`
                 result: None,
                 operator_stack: Vec::new(),
                 output_queue: VecDeque::new()
@@ -85,22 +88,20 @@ impl Term {
 
     /// Prepare the term for the processing.
     pub fn prepare(&mut self) -> Result<()> {
-        // TODO: shunting yard
+        trace!("preparing term: {:#?}", self);
+        self.text = Self::filter(&self.original)?;
 
         // Storage for unfinished tokens
         let mut unfinished_chars: Vec<char> = Vec::new();
 
         for (index, c) in self.original.chars().enumerate() {
-            if !c.is_alphanumeric() {
-                // TODO: allow any unicode char to be a variable
-                warn!("'{c}' is not a valid character, only alphanumeric input is allowed.");
-                return Err(Error::SyntaxError);
-            }
             // this will be a mess, but it has to be before i can sort the mess.
             match c {
+                // TODO: make function to check if character is an operator, use it
                 _ => {
-                    warn!("The meaning of '{c}' could not be identified.");
-                    return Err(Error::SyntaxError);
+                    let reason = format!("The meaning of '{c}' could not be identified.");
+                    warn!(reason);
+                    return Err(Error::SyntaxError(reason));
                 }
             }
         }
@@ -125,14 +126,54 @@ impl Term {
     }
 
     /// only leave relevant chars for calculation
-    fn filter(s: String) -> String {
+    // TODO: make function to check if character is an operator, use it
+    fn filter(s: &str) -> Result<String> {
+        // pre checks
+        // NOTE: Apperently, "alphanumeric" in Rust is a pretty broad term.
+        // Even CJK characters or Japanese Kana are allowed:
+        // - 'さ' alphanumeric
+        // - '数' alphanumeric
+        // - '学' alphanumeric
+        // - '+'  not alphanumeric
+        for c in s.chars() {
+            #[cfg(debug_assertions)] {
+                debug!("filter checks for '{c}':
+                alphanumeric:       {}
+                allowed special:    {}
+                EXCEPT IF
+                ascii control:      {}
+                ",
+                !c.is_alphanumeric(),
+                !Self::is_allowed_special_c(&c),
+                c.is_ascii_control(),
+            )
+            }
+            if
+                (
+                    !c.is_alphanumeric()                    ||
+                    !Self::is_allowed_special_c(&c)
+                )
+                &&
+                (
+                    c.is_ascii_control()
+                )
+            {
+                // TODO: allow any unicode char to be a variable
+                let reason = format!("'{c}' is not a valid character, only alphanumeric, punctuation, operators are allowed.");
+                warn!(reason);
+                return Err(Error::SyntaxError(reason));
+            }
+        }
+
+        // filter out single chars
         let mut filtered = String::new();
         for c in s.chars() {
             if !Self::is_ignore(&c) {
                 filtered.push(c);
             }
         }
-        return filtered
+
+        return Ok(filtered)
     }
 
     /// check if we should ignore this character
@@ -142,6 +183,14 @@ impl Term {
             _ => false
         }
     }
+
+    /// allowed special chars
+    fn is_allowed_special_c(c: &char) -> bool {
+        match *c {
+            '+' | '-' | '*' | '/' | '%' => true,
+            _ => false
+        }
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////