exercises(grains): remove test for negative input (#210)

Author: ee7

exercises/practice/grains/.meta/config.json

@@ -2,6 +2,9 @@
   "authors": [
     "massivelivefun"
   ],
+  "contributors": [
+    "ee7"
+  ],
   "files": {
     "solution": [
       "grains.zig"

exercises/practice/grains/.meta/example.zig

@@ -5,11 +5,11 @@ pub const ChessboardError = error{IndexOutOfBounds};
 
 const number_of_chess_squares = 64;
 
-pub fn square(index: isize) ChessboardError!u64 {
-    if (index > number_of_chess_squares or index <= 0) {
+pub fn square(index: usize) ChessboardError!u64 {
+    if (index > number_of_chess_squares or index == 0) {
         return ChessboardError.IndexOutOfBounds;
     }
-    return @as(u64, 1) << @truncate(u6, @bitCast(usize, index) - 1);
+    return @as(u64, 1) << @truncate(u6, index - 1);
 }
 
 pub fn total() u64 {

exercises/practice/grains/.meta/tests.toml

@@ -35,6 +35,7 @@ description = "returns the number of grains on the square -> square 0 raises an
 
 [61974483-eeb2-465e-be54-ca5dde366453]
 description = "returns the number of grains on the square -> negative square raises an exception"
+include = false
 
 [a95e4374-f32c-45a7-a10d-ffec475c012f]
 description = "returns the number of grains on the square -> square greater than 64 raises an exception"

exercises/practice/grains/grains.zig

@@ -1,4 +1,4 @@
-pub fn square(index: isize) ChessboardError!u64 {
+pub fn square(index: usize) ChessboardError!u64 {
     _ = index;
     @compileError("please implement the square function");
 }

exercises/practice/grains/test_grains.zig

@@ -52,12 +52,6 @@ test "square 0 produces an error" {
     try testing.expectError(expected, actual);
 }
 
-test "negative square produces an error" {
-    const expected = ChessboardError.IndexOutOfBounds;
-    const actual = comptime grains.square(-1);
-    try testing.expectError(expected, actual);
-}
-
 test "square greater than 64 produces an error" {
     const expected = ChessboardError.IndexOutOfBounds;
     const actual = comptime grains.square(65);