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[Bug 14861] LCB: Add "reverse _" syntax for sequence types (String, List, Data) #5328
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This is useful when `MCAutoValueRefBase`-derived managed pointers are used in the implementation of libfoundation. `t_string->chars` is a lot clearer than `(*t_string)->chars`.
Add a private template that provides in-place reverse for an array. The algorithm works from the middle of the array, working outwards and swapping elements between the front and the back. It can only be used for types that are suitable for use with `std::swap()`; either trivially copyable, or with an implementation of `T::swap(T& other)`.
Add a function that reverses a mutable list instance in place.
Add a function that reverses the order of bytes in a mutable `MCData` instance in-place.
Strings cannot be reversed in-place in the general case. There is no upper limit on the number of codeunits in a grapheme, which means that a temporary buffer of at the same length of the string is required for general correctness. This patch adds a "reversed copy" function which performs a deep copy of the source string, and then constructs the reversed form in the copy by re-reading from the source string via a grapheme break iterator. In practice, the "trivial" flag is not getting set for trivial strings, so all strings that use UTF-16 internal representatino go through the slow grapheme break iterator path.
Add the ability to reverse a binary string in an LCB program with a new `reverse tData` statement.
Add the ability to reverse the order of bytes in a list with the `reverse tList` statement.
Add a new function to reverse an LCB string in-place using the `reverse tString` statement.
Now that there is a `reverse` statement, provide an alternative example of looping over the contents of a string.
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@peter-b, thanks for your PR! By analyzing the history of the files in this pull request, we identified @livecodeian, @runrevmark and @livecodesebastien to be potential reviewers. |
The newly-introduced `MCInplaceReverse()` function requires `<utility>` to get `std::swap()`.
livecodeali
reviewed
Apr 5, 2017
| * unichar_t codeunits items per grapheme. In this case, we | ||
| * reverse by iterating over the contents of the original | ||
| * string, copying the graphemes into the new string. */ | ||
| MCStringRef t_original = __MCStringIsIndirect(self) ? self->string : self; |
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Please avoid using the ternary conditional operator
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@livecode-vulcan review ok de86d30 |
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💙 review by @livecodeali ok de86d30 |
livecode-vulcan
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Apr 5, 2017
[Bug 14861] LCB: Add "reverse _" syntax for sequence types (String, List, Data) This patch adds in-place `reverse _` syntax to LCB for sequence types (`List`, `String` and `Data`). ``` variable tList put [1, 2, 3] into tList reverse tList expect that tList is [3, 2, 1] ``` There are several components: - An `MCInplaceReverse()` template function for libfoundation internal use that supports any type that has a `swap()` operation - In-place `MCProperListReverse()` and `MCDataReverse()` functions which operate on mutable values - `MCStringCopyReverse()`, which creates a copy of a string with the order of its _graphemes_ reversed - LCB syntax definitions, documentation, examples and unit tests
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😎 test success de86d30
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This patch adds in-place
reverse _syntax to LCB for sequence types (List,StringandData).There are several components:
MCInplaceReverse()template function for libfoundation internal use that supports any type that has aswap()operationMCProperListReverse()andMCDataReverse()functions which operate on mutable valuesMCStringCopyReverse(), which creates a copy of a string with the order of its graphemes reversed