[test] Add separate testing files for __int__, __float__, __str__ (#34)

This pull request includes several changes to the `DeciMojo` library,
focusing on code cleanup, new test additions, and minor optimizations.
The most important changes include the addition of a new test case, a
fix in the `Decimal` struct, and the removal of unnecessary comment
lines.

### New test additions:
*
[`mojoproject.toml`](diffhunk://#diff-1b0ef62120bccf4c05a76e60e13fe686f33eb92d5897b3f05e0c3f8d737fc5c0R43):
Added a new test case `test_to_float` to the test suite.

### Test removal:
*
[`tests/test_conversions.mojo`](diffhunk://#diff-d43bab99eda0af629ae4f094121805ed00644a6fa4ff98de5d068111ff7e7738L1-L129):
Removed the entire file containing tests for Decimal conversion methods
and split it into `test_to_string` and `test_to_int`.

### Code optimizations:
*
[`src/decimojo/decimal.mojo`](diffhunk://#diff-c2178e6e0bbbbb0d3379f1513412224309d1232c444654e77abb5ce36b3a854fL970-R968):
Fixed the `to_float` method in the `Decimal` struct to correctly use
`Float64(10)` for division, ensuring proper floating-point arithmetic.

### Documentation updates:
*
[`docs/todo.md`](diffhunk://#diff-d84697334acf64fe5d67dfd34f6370dca462f602aa3a720711eae12bf8dd153dL5-R5):
Marked the optimization task for the `exp()` function as completed.

Author: forfudan

docs/todo.md

@@ -2,4 +2,4 @@
 
 This is a to-do list for Yuhao's personal use.
 
-- The `exp()` function performs slower than Python's counterpart in specific cases. Detailed investigation reveals the bottleneck stems from multiplication operations between decimals with significant fractional components. These operations currently rely on UInt256 arithmetic, which introduces performance overhead. Optimization of the `multiply()` function is required to address these performance bottlenecks, particularly for high-precision decimal multiplication with many digits after the decimal point.
+- [x] (#31) The `exp()` function performs slower than Python's counterpart in specific cases. Detailed investigation reveals the bottleneck stems from multiplication operations between decimals with significant fractional components. These operations currently rely on UInt256 arithmetic, which introduces performance overhead. Optimization of the `multiply()` function is required to address these performance bottlenecks, particularly for high-precision decimal multiplication with many digits after the decimal point.

mojoproject.toml

@@ -40,6 +40,7 @@ test_round = "magic run package && magic run mojo test tests/test_round.mojo &&
 test_creation = "magic run package && magic run mojo test tests/test_creation.mojo && magic run delete_package"
 test_from_float = "magic run package && magic run mojo test tests/test_from_float.mojo && magic run delete_package"
 test_from_string = "magic run package && magic run mojo test tests/test_from_string.mojo && magic run delete_package"
+test_to_float = "magic run package && magic run mojo test tests/test_to_float.mojo && magic run delete_package"
 test_comparison = "magic run package && magic run mojo test tests/test_comparison.mojo && magic run delete_package"
 test_factorial = "magic run package && magic run mojo test tests/test_factorial.mojo && magic run delete_package"
 test_exp = "magic run package && magic run mojo test tests/test_exp.mojo && magic run delete_package"

src/decimojo/__init__.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #
 
 """

src/decimojo/arithmetics.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #
 #
 # Implements basic arithmetic functions for the Decimal type

src/decimojo/comparison.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #
 #
 # Implements comparison operations for the Decimal type

src/decimojo/decimal.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #
 #
 # Implements basic object methods for the Decimal type
@@ -967,7 +965,7 @@ struct Decimal(
             The floating-point representation of this Decimal.
         """
 
-        var result = Float64(self.coefficient()) / (10 ** self.scale())
+        var result = Float64(self.coefficient()) / (Float64(10) ** self.scale())
         result = -result if self.is_negative() else result
 
         return result

src/decimojo/exponential.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #
 #
 # Implements exponential functions for the Decimal type

src/decimojo/prelude.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #
 
 """

src/decimojo/rounding.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #
 #
 # Implements basic object methods for the Decimal type

src/decimojo/rounding_mode.mojo

@@ -1,5 +1,4 @@
 # ===----------------------------------------------------------------------=== #
-#
 # DeciMojo: A fixed-point decimal arithmetic library in Mojo
 # https://github.com/forFudan/DeciMojo
 #
@@ -16,7 +15,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-#
 # ===----------------------------------------------------------------------=== #