Xiaodi Wu
June 17, 2017
The design, re-design, and implementation of [SE-0104][1], a proposal to revise integer protocols in Swift, is now largely complete in shipping previews of Swift 4. As an exercise, I have used the new APIs to develop a [set of additional numeric facilities][2]. Here are some insights gained from that experience--and from two unpublished exercises to implement a BigInt type (one from scratch, one wrapping GMP)--as well as suggestions for improvement.
Extracted from UTN28
"The following table gives the default math keywords, their target characters and codes along with spacing and linear-format build-up properties."
Omitted from the original table are operands, enclosures, spaces, big/long variants, and non-NFKC characters. Three characters that default to their emoji variants on iOS, and one related character, are excised.
| Keyword | Glyph | Code | Spacing | LF Property |
|---|---|---|---|---|
| pm | ± | U+00B1 | unary/binary | unary/binary |
| times | × | U+00D7 | binarynsp | normal |
| Glyph | Code | Description |
|---|---|---|
| ! | U+0021 | EXCLAMATION MARK |
| % | U+0025 | PERCENT SIGN |
| & | U+0026 | AMPERSAND |
| * | U+002A | ASTERISK |
| + | U+002B | PLUS SIGN |
| - | U+002D | HYPHEN-MINUS |
| / | U+002F | SOLIDUS |
| < | U+003C | LESS-THAN SIGN |
During the review process, add the following fields as needed:
| import argparse | |
| import sys | |
| from functools import reduce | |
| from typing import Iterator | |
| def encode(raw: str) -> int: | |
| return reduce(lambda x, y: x * 8 + y, | |
| map(lambda x: x % 32 % 5 + 3, raw.encode())) | |
| def _decode(cooked: int) -> Iterator[int]: |