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[RFC] Minor edits to the text.

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Alessandro Coglio 2021-10-05 21:01:47 -07:00
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11
docs/rfc/004-integer-type-casts.md
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@ -72,9 +72,7 @@ exponential-expression = cast-expression
``` ```
There is no need to modify the `keyword` rule There is no need to modify the `keyword` rule
because it already includes `as` as one of the keywords. because it already includes `as` as one of the keywords.
Note the use of `integer-type` in the `cast-expression` rule; Note the use of `integer-type` in the `cast-expression` rule.
an alternative is to use `type` there
and check post-parsing that the type is in fact an integer one.
The above grammar rules imply that casts bind The above grammar rules imply that casts bind
tighter than binary operators and looser than unary operators. tighter than binary operators and looser than unary operators.
@ -111,8 +109,7 @@ but cause errors when values are not representable in the new types;
and _values-changing casts_, and _values-changing casts_,
which never cause errors but may change the mathematical values. which never cause errors but may change the mathematical values.
Based on discussion and consensus within the Leo team, This RFC proposes value-preserving casts;
this RFC proposes value-preserving casts;
value-changing casts are discussed in the 'Alternatives' section, value-changing casts are discussed in the 'Alternatives' section,
for completeness. for completeness.
@ -129,7 +126,7 @@ When values are to be changed, separate (built-in) functions can be used,
e.g. to mask bits and achieve the same effect as e.g. to mask bits and achieve the same effect as
the value-changing casts discussed below. the value-changing casts discussed below.
This approach Leo's treatment of potentially erroneous situations like integer overflows. This approach is consistent with Leo's treatment of potentially erroneous situations like integer overflows.
The principle is that developers should explicitly use The principle is that developers should explicitly use
operations that may overflow if that is their intention, operations that may overflow if that is their intention,
rather than having those situation possibly occur unexpectedly. rather than having those situation possibly occur unexpectedly.
@ -201,7 +198,7 @@ As mentioned above, an alternative semantics for casts is value-changing:
10. `iN` to `uN`: re-interpret as unsigned 10. `iN` to `uN`: re-interpret as unsigned
Except for the 1st and 3rd cases, the value may change. Except for the 1st and 3rd cases, the value may change.
This approach is common in other programming languages. This value-changing approach is common in other programming languages.
However, it should be noted that other programming languages However, it should be noted that other programming languages
typically do not check for overflow in integer operations either typically do not check for overflow in integer operations either
(at least, not for production code). (at least, not for production code).