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Text formatting: a leading zero on the minimum width should really mean leading zero #39997
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Seems reasonable to me, as documented:
The precise definition of "sign aware" isn't really specified and this seems like a great interpretation to me (changing the first example above to |
Now it always implies right-alignment, so that padding zeroes are placed after the sign (if any) and before the digits. In other words, it always takes precedence over explicitly specified `[[fill]align]`. This also affects the '#' flag: zeroes are placed after the prefix (0b, 0o, 0x) and before the digits. :05 :<05 :>05 :^05 before |-0001| |-1000| |-0001| |-0100| after |-0001| |-0001| |-0001| |-0001| :#05x :<#05x :>#05x :^#05x before |0x001| |0x100| |000x1| |0x010| after |0x001| |0x001| |0x001| |0x001| Fixes rust-lang#39997 [breaking-change]
Change how the `0` flag works in format! Now it always implies right-alignment, so that padding zeroes are placed after the sign (if any) and before the digits. In other words, it always takes precedence over explicitly specified `[[fill]align]`. This also affects the '#' flag: zeroes are placed after the prefix (0b, 0o, 0x) and before the digits. Here's a short summary of how similar format strings work in Python and Rust: ``` :05 :<05 :>05 :^05 Python 3.6 |-0001| |-1000| |000-1| |0-100| Rust before |-0001| |-1000| |-0001| |-0100| Rust after |-0001| |-0001| |-0001| |-0001| :#05x :<#05x :>#05x :^#05x Python 3.6 |0x001| |0x100| |000x1| |00x10| Rust before |0x001| |0x100| |000x1| |0x010| Rust after |0x001| |0x001| |0x001| |0x001| ``` Fixes rust-lang#39997 [breaking-change]
Change how the `0` flag works in format! Now it always implies right-alignment, so that padding zeroes are placed after the sign (if any) and before the digits. In other words, it always takes precedence over explicitly specified `[[fill]align]`. This also affects the '#' flag: zeroes are placed after the prefix (0b, 0o, 0x) and before the digits. Here's a short summary of how similar format strings work in Python and Rust: ``` :05 :<05 :>05 :^05 Python 3.6 |-0001| |-1000| |000-1| |0-100| Rust before |-0001| |-1000| |-0001| |-0100| Rust after |-0001| |-0001| |-0001| |-0001| :#05x :<#05x :>#05x :^#05x Python 3.6 |0x001| |0x100| |000x1| |00x10| Rust before |0x001| |0x100| |000x1| |0x010| Rust after |0x001| |0x001| |0x001| |0x001| ``` Fixes rust-lang#39997 [breaking-change]
Change how the `0` flag works in format! Now it always implies right-alignment, so that padding zeroes are placed after the sign (if any) and before the digits. In other words, it always takes precedence over explicitly specified `[[fill]align]`. This also affects the '#' flag: zeroes are placed after the prefix (0b, 0o, 0x) and before the digits. Here's a short summary of how similar format strings work in Python and Rust: ``` :05 :<05 :>05 :^05 Python 3.6 |-0001| |-1000| |000-1| |0-100| Rust before |-0001| |-1000| |-0001| |-0100| Rust after |-0001| |-0001| |-0001| |-0001| :#05x :<#05x :>#05x :^#05x Python 3.6 |0x001| |0x100| |000x1| |00x10| Rust before |0x001| |0x100| |000x1| |0x010| Rust after |0x001| |0x001| |0x001| |0x001| ``` Fixes rust-lang#39997 [breaking-change]
Change how the `0` flag works in format! Now it always implies right-alignment, so that padding zeroes are placed after the sign (if any) and before the digits. In other words, it always takes precedence over explicitly specified `[[fill]align]`. This also affects the '#' flag: zeroes are placed after the prefix (0b, 0o, 0x) and before the digits. Here's a short summary of how similar format strings work in Python and Rust: ``` :05 :<05 :>05 :^05 Python 3.6 |-0001| |-1000| |000-1| |0-100| Rust before |-0001| |-1000| |-0001| |-0100| Rust after |-0001| |-0001| |-0001| |-0001| :#05x :<#05x :>#05x :^#05x Python 3.6 |0x001| |0x100| |000x1| |00x10| Rust before |0x001| |0x100| |000x1| |0x010| Rust after |0x001| |0x001| |0x001| |0x001| ``` Fixes rust-lang#39997 [breaking-change]
Change how the `0` flag works in format! Now it always implies right-alignment, so that padding zeroes are placed after the sign (if any) and before the digits. In other words, it always takes precedence over explicitly specified `[[fill]align]`. This also affects the '#' flag: zeroes are placed after the prefix (0b, 0o, 0x) and before the digits. Here's a short summary of how similar format strings work in Python and Rust: ``` :05 :<05 :>05 :^05 Python 3.6 |-0001| |-1000| |000-1| |0-100| Rust before |-0001| |-1000| |-0001| |-0100| Rust after |-0001| |-0001| |-0001| |-0001| :#05x :<#05x :>#05x :^#05x Python 3.6 |0x001| |0x100| |000x1| |00x10| Rust before |0x001| |0x100| |000x1| |0x010| Rust after |0x001| |0x001| |0x001| |0x001| ``` Fixes rust-lang#39997 [breaking-change]
#40729 is related and can be closed. |
In a string format, the leading zero on a minimum width is treated as a padding character. It would make more sense for it to be treated strictly as a leading zero. The status quo permits strange things like this:
Either
" 1"
or"0001"
would be better answers than one that changes the numeric value.Just to be clear, I agree that this behavior is correct:
This case uses
0
as its padding character, so you deserve whatever you get.The text was updated successfully, but these errors were encountered: