Joseph Ferano
4fe2f36d98
Finishing the text family the previous lane started. All three are over [u8] and none of them allocates, which is what decides their shapes. trim answers a slice of its input. That is the only shape available without an allocator, and it is also the better one: there is no new storage, only a narrower view of the caller's, so the result dies with its owner and trimming modifies nothing. Both loops test (< lo hi), because an all-whitespace input otherwise walks lo past hi and (slice s lo hi) traps on a reversed range - the same trap the bounds table already asserts on. That input is in the case list. index-of-bytes is naive and stays naive. Boyer-Moore wants a skip table sized by the needle, which is an array, which is an allocation. The empty needle answers Some 0 so that index-of-bytes and starts-with? agree on every needle, and the length test returns before the loop so a needle longer than the haystack cannot build a window off the end. parse-f64 splits the work where the two halves actually differ: the grammar is Flan's and the rounding is libc's. parse-i64 is entirely Flan because strtoll's answers are wrong for a caller - 0 for "", 0 for "abc", 12 for "12x" - and not because decimal-to-binary conversion is suspect. Reimplementing correctly rounded conversion is a different and much larger problem than rejecting junk, and IEEE-754 already guarantees strtod gives the same bits everywhere. So this validates the whole slice and only a slice that is entirely a number reaches bytes->f64. Every refusal in the table - "", "abc", "1x", ".", "1e", " 1", "1 ", "0x10", "nan" - is a plausible number out of strtod. Two caveats, both written into the source rather than discovered later. The locale worry that keeps parse-i64 in Flan does apply to strtod's decimal point, and is moot only because nothing in the runtime calls setlocale; if that stops being true this is what breaks. And the length is capped at 511 because flan_bytes_to_f64 truncates there - a validator that approved 600 digits would be approving a different number than the one strtod reads. digit? and space? exist because parse-f64 and trim need them, and calc-me loses its own byte-identical digit?. One top-level namespace makes the second definition an error rather than a shadow, which is the rule doing its job: two copies that later drift apart is exactly what it prevents.
