Change digits from isize to i8

src/number.rs

@@ -15,7 +15,7 @@ pub enum Sign {
 
 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 pub struct Number {
-    pub digits: Vec<isize>,
+    pub digits: Vec<i8>,
     pub sign: Sign,
 }
 
@@ -26,9 +26,9 @@ impl Number {
         (n % modulo) / divisor
     }
 
-    pub const fn byte_to_digit(b: u8) -> isize {
+    pub const fn byte_to_digit(b: u8) -> i8 {
         // wrapping_sub('0' as u32) same as - 48 but less magical
-        (b as isize).wrapping_sub('0' as isize)
+        (b as i8).wrapping_sub('0' as i8)
     }
 
     pub fn pow(self, n: u32) -> Self {
@@ -48,6 +48,13 @@ impl Number {
         }
     }
 
+    pub fn ten_pow(self, n: u32) -> Self {
+        Number {
+            digits: [vec![0; n as usize], self.digits].concat(),
+            sign: self.sign,
+        }
+    }
+
     pub fn fact(self) -> Self {
         let mut fact = Number::from(1);
         if ((self.digits.len() * 8) as u32) < isize::BITS {
@@ -107,4 +114,28 @@ mod number_tests {
         assert_eq!(digit_4, 2);
         assert_eq!(digit_5, 1);
     }
+
+    #[test]
+    fn test_pow() {
+        let num = Number::from(2);
+        assert_eq!(Number::from(16), num.pow(4));
+    }
+
+    #[test]
+    fn test_ten_pow_zero() {
+        let num = Number::from(2);
+        assert_eq!(Number::from(2), num.ten_pow(0));
+    }
+
+    #[test]
+    fn test_ten_pow_one() {
+        let num = Number::from(2);
+        assert_eq!(Number::from(20), num.ten_pow(1));
+    }
+
+    #[test]
+    fn test_ten_pow_two() {
+        let num = Number::from(2);
+        assert_eq!(Number::from(200), num.ten_pow(2));
+    }
 }

src/number/add.rs

@@ -16,7 +16,7 @@ impl Add for Number {
         let mut rhs_digits = rhs.digits.clone();
         if self_len != rhs_len {
             let difference = (self_len).abs_diff(rhs_len);
-            let pad = vec![0isize; difference];
+            let pad = vec![0i8; difference];
             if min(self_len, rhs_len) == self_len {
                 self_digits = [self.digits, pad].concat();
             } else {

src/number/from.rs

@@ -8,7 +8,7 @@ impl TryFrom<Number> for isize {
     fn try_from(value: Number) -> Result<Self, Self::Error> {
         let mut num = 0;
         for (pos, &digit) in value.digits.iter().enumerate() {
-            let mul = digit.checked_mul(10isize.pow(pos as u32));
+            let mul = (digit as isize).checked_mul(10isize.pow(pos as u32));
             if mul.is_none() {
                 return Err(Box::from("Cannot convert Number to isize. Too big."));
             }
@@ -62,7 +62,7 @@ impl From<isize> for Number {
         let num_len = (value as f64 + 1.0).log10().ceil() as usize;
         let mut digits = vec![];
         for digit_idx in 0..num_len {
-            let digit = Self::get_digit(value, digit_idx);
+            let digit = Self::get_digit(value, digit_idx) as i8;
             digits.push(digit);
         }
         let digits = digits.to_vec();

src/number/sub.rs

@@ -16,7 +16,7 @@ impl Sub for Number {
         let mut rhs_digits = rhs.digits.clone();
         if self_len != rhs_len {
             let difference = (self_len).abs_diff(rhs_len);
-            let pad = vec![0isize; difference];
+            let pad = vec![0i8; difference];
             if min(self_len, rhs_len) == self_len {
                 self_digits = [self.digits, pad].concat();
             } else {