fix: comparison; cairo syntax (#135)

Author: tserg

not-so-smart-contracts/cairo/incorrect_felt_comparison/README.md

@@ -1,40 +1,40 @@
 # Incorrect Felt Comparison
 
-In cairo, there are two methods for comparison, in particular for the less than or equal to operator we have the methods `assert_le` and `assert_nn_le`. `assert_le` asserts that a number a is less than or equal to b, regardless of the size of a, while `assert_nn_le` will also assert that a is non-negative, ie not greater than the `RANGE_CHECK_BOUND` value of `2^128`: https://github.com/starkware-libs/cairo-lang/blob/master/src/starkware/cairo/common/math.cairo#L66-L67
+In Cairo, there are two builtin methods for the less than or equal to comparison operator: `assert_le` and `assert_nn_le`. `assert_le` asserts that a number `a` is less than or equal to `b`, regardless of the size of `a`, while `assert_nn_le` additionally asserts that `a` is non-negative, i.e. not greater than or equal to the `RANGE_CHECK_BOUND` value of `2^128`: https://github.com/starkware-libs/cairo-lang/blob/master/src/starkware/cairo/common/math.cairo#L66-L67
 
 # Example
 
-Suppose that a codebase uses the following checks regarding a hypothetical ERC20 token. In the first function, it may be possible that `value` is in fact greater than `max_supply`, yet because the function does not verify `value <0` the assertion will incorrectly pass. The second function, however, asserts that `0 < value < max_supply`, which will correctly not let an incorrect `value` go through the assertion.
+Suppose that a codebase uses the following checks regarding a hypothetical ERC20 token. In the first function, it may be possible that `value` is in fact greater than `max_supply`, yet because the function does not verify `value >= 0` the assertion will incorrectly pass. The second function, however, asserts that `0 <= value <= max_supply`, which will correctly not let an incorrect `value` go through the assertion.
 
 ```cairo
 @storage_var
-func max_supply() -> (res: felt):
-end
+func max_supply() -> (res: felt) {
+}
 
 @external
-func bad_comparison{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}():
-    let (value: felt) = ERC20.total_supply()
-    assert_le{range_check_ptr=range_check_ptr}(value, max_supply.read())
+func bad_comparison{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}() {
+    let (value: felt) = ERC20.total_supply();
+    assert_le{range_check_ptr=range_check_ptr}(value, max_supply.read());
 
-   # do something...
+    // do something...
 
-    return ()
-end
+    return ();
+}
 
 @external
-func better_comparison{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}():
-    let (value: felt) = ERC20.total_supply()
-    assert_nn_le{range_check_ptr=range_check_ptr}(value, max_supply.read())
+func better_comparison{syscall_ptr : felt*, pedersen_ptr : HashBuiltin*, range_check_ptr}() {
+    let (value: felt) = ERC20.total_supply();
+    assert_nn_le{range_check_ptr=range_check_ptr}(value, max_supply.read());
 
-   # do something...
+    // do something...
 
-    return ()
+    return ();
 
     
-end
+}
 ```
 
 
 
 # Mitigations
-Review all felt comparisons closely. Determine what sort of behavior the comparison should have, and if `assert_nn_le` is more appropriate.
+Review all felt comparisons closely. Determine what sort of behavior the comparison should have, and if `assert_nn_le` is more appropriate.