tests in the steel decimal crate with serious issue fixed

steel_decimal/src/functions.rs

@@ -75,23 +75,32 @@ fn parse_scientific_notation(s: &str) -> Result<Decimal, String> {
     Ok(result)
 }
 
-// Basic arithmetic operations (now precision-aware)
+// Basic arithmetic operations
 pub fn decimal_add(a: String, b: String) -> Result<String, String> {
     let a_dec = parse_decimal(&a)?;
     let b_dec = parse_decimal(&b)?;
-    Ok(format_result(a_dec + b_dec))
+
+    a_dec.checked_add(b_dec)
+        .map(|result| format_result(result))
+        .ok_or_else(|| "Addition overflowed".to_string())
 }
 
 pub fn decimal_sub(a: String, b: String) -> Result<String, String> {
     let a_dec = parse_decimal(&a)?;
     let b_dec = parse_decimal(&b)?;
-    Ok(format_result(a_dec - b_dec))
+
+    a_dec.checked_sub(b_dec)
+        .map(|result| format_result(result))
+        .ok_or_else(|| "Subtraction overflowed".to_string())
 }
 
 pub fn decimal_mul(a: String, b: String) -> Result<String, String> {
     let a_dec = parse_decimal(&a)?;
     let b_dec = parse_decimal(&b)?;
-    Ok(format_result(a_dec * b_dec))
+
+    a_dec.checked_mul(b_dec)
+        .map(|result| format_result(result))
+        .ok_or_else(|| "Multiplication overflowed".to_string())
 }
 
 pub fn decimal_div(a: String, b: String) -> Result<String, String> {
@@ -102,7 +111,9 @@ pub fn decimal_div(a: String, b: String) -> Result<String, String> {
         return Err("Division by zero".to_string());
     }
 
-    Ok(format_result(a_dec / b_dec))
+    a_dec.checked_div(b_dec)
+        .map(|result| format_result(result))
+        .ok_or_else(|| "Division overflowed".to_string())
 }
 
 // Precision control functions