Start implementing parsing numbers from strings

src/bigint.rs

@@ -128,7 +128,28 @@ impl BigInt {
     /// Convert a `&str` or a `String` representing a number in the specified radix to a Bigint.
     ///
     /// For radix 10, use the `from` associated function instead.
+    ///
+    /// Radix must be between 1 and 36, inclusive, with radix higher
+    /// than 11 represented by A-Z
+    ///
+    /// Only alphanumeric characters are considered, so exponents and
+    /// other forms are not parsed
     pub fn from_str_radix<T: ToString>(s: T, radix: usize) -> BigInt {
+        let input = s.to_string();
+
+        // Convert each digit to it's decimal representation
+        let mut raw_digits: Vec<usize> = Vec::with_capacity(input.len());
+        for maybe_digit in input.chars() {
+            match maybe_digit.to_digit(radix as u32) {
+                Some(d) => raw_digits.push(d as usize),
+                None => continue,
+            }
+        }
+
+        // Calculate the decimal value by calculating the value
+        // of each place value
+
+        // In base 1, number of place values = total value
         todo!();
     }