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strformat: support 'sign' as Python does

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This commit is contained in:
Araq
2017-12-17 17:58:04 +01:00
parent 5c7493f833
commit 2e61e6edf9
1 changed files with 36 additions and 25 deletions
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61
lib/pure/strformat.nim
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@@ -92,7 +92,7 @@ Standard format specifier
The general form of a standard format specifier is::
[[fill]align][#][0][minimumwidth][.precision][type]
[[fill]align][sign][#][0][minimumwidth][.precision][type]
The brackets ([]) indicate an optional element.
@@ -116,6 +116,18 @@ The optional 'fill' character defines the character to be used to pad
the field to the minimum width. The fill character, if present, must be
followed by an alignment flag.
The 'sign' option is only valid for numeric types, and can be one of the following:
================= ====================================================
Sign Meaning
================= ====================================================
``+`` Indicates that a sign should be used for both
positive as well as negative numbers.
``-`` Indicates that a sign should be used only for
negative numbers (this is the default behavior).
`` `` (space) Indicates that a leading space should be used on
positive numbers.
If the '#' character is present, integers use the 'alternate form' for formatting.
This means that binary, octal, and hexadecimal output will be prefixed
with '0b', '0o', and '0x', respectively.
@@ -273,6 +285,7 @@ macro fmt*(pattern: string): untyped =
check fmt"{10}", "10"
check fmt"{16:#X}", "0x10"
check fmt"{16:^#7X}", " 0x10 "
check fmt"{16:^+#7X}", " +0x10 "
# Hex tests
check fmt"{0:x}", "0"
@@ -292,6 +305,8 @@ macro fmt*(pattern: string): untyped =
check fmt"{123.456}", "123.456"
check fmt"{-123.456}", "-123.456"
check fmt"{123.456:.3f}", "123.456"
check fmt"{123.456:+.3f}", "+123.456"
check fmt"{-123.456:+.3f}", "-123.456"
check fmt"{-123.456:.3f}", "-123.456"
check fmt"{123.456:1g}", "123.456"
check fmt"{123.456:.1f}", "123.5"
@@ -417,8 +432,7 @@ proc alignString*(s: string, minimumWidth: int; align = '<'; fill = ' '): string
type
StandardFormatSpecifier* = object ## Type that describes "standard format specifiers".
fill*, align*: char ## Desired fill and alignment.
when false:
sign: char ## Desired sign.
sign*: char ## Desired sign.
alternateForm*: bool ## Whether to prefix binary, octal and hex numbers
## with ``0b``, ``0o``, ``0x``.
padWithZero*: bool ## Whether to pad with zeros rather than spaces.
@@ -461,24 +475,23 @@ proc formatInt(n: SomeNumber; radix: int; spec: StandardFormatSpecifier): string
result.add(mkDigit(d.int, spec.typ))
for idx in 0..<(result.len div 2):
swap result[idx], result[result.len - idx - 1]
let adjustedWid = if negative: spec.minimumWidth - 1 else: spec.minimumWidth
if spec.padWithZero:
let toFill = spec.minimumWidth - result.len - xx.len - ord(negative)
let sign = negative or spec.sign != '-'
let toFill = spec.minimumWidth - result.len - xx.len - ord(sign)
if toFill > 0:
result = repeat('0', toFill) & result
if negative:
result = "-" & xx & result
elif spec.sign != '-':
result = spec.sign & xx & result
else:
result = xx & result
if spec.align == '<':
if negative:
result = "-" & xx & result
else:
result = xx & result
for i in result.len..<spec.minimumWidth:
result.add(spec.fill)
else:
if negative:
result = "-" & xx & result
else:
result = xx & result
let toFill = spec.minimumWidth - result.len
if spec.align == '^':
let half = toFill div 2
@@ -492,7 +505,7 @@ proc parseStandardFormatSpecifier*(s: string; start = 0;
## An exported helper proc that parses the "standard format specifiers",
## as specified by the grammar::
##
## [[fill]align][#][0][minimumwidth][.precision][type]
## [[fill]align][sign][#][0][minimumwidth][.precision][type]
##
## This is only of interest if you want to write a custom ``format`` proc that
## should support the standard format specifiers. If ``ignoreUnknownSuffix`` is true,
@@ -500,6 +513,7 @@ proc parseStandardFormatSpecifier*(s: string; start = 0;
const alignChars = {'<', '>', '^'}
result.fill = ' '
result.align = '<'
result.sign = '-'
var i = start
if i + 1 < s.len and s[i+1] in alignChars:
result.fill = s[i]
@@ -509,11 +523,9 @@ proc parseStandardFormatSpecifier*(s: string; start = 0;
result.align = s[i]
inc i
when false:
# XXX Python inspired 'sign' not yet supported!
if i < s.len and s[i] in {'-', '+', ' '}:
result.sign = s[i]
inc i
if i < s.len and s[i] in {'-', '+', ' '}:
result.sign = s[i]
inc i
if i < s.len and s[i] == '#':
result.alternateForm = true
@@ -578,12 +590,11 @@ proc format*(value: SomeReal; specifier: string; res: var string) =
"invalid type in format string for number, expected one " &
" of 'e', 'E', 'f', 'F', 'g', 'G' but got: " & spec.typ)
#let result = if spec.minimumWidth > 0 and spec.align == '<' and value < 0 and spec.padWithZero:
# "-" & alignString(formatBiggestFloat(-value, fmode, spec.precision), spec.minimumWidth-1,
# spec.align, '0')
#else:
let result = alignString(formatBiggestFloat(value, fmode, spec.precision), spec.minimumWidth,
spec.align, spec.fill)
var f = formatBiggestFloat(value, fmode, spec.precision)
if value >= 0.0 and spec.sign != '-':
f = spec.sign & f
let result = alignString(f, spec.minimumWidth,
spec.align, spec.fill)
if spec.typ in {'A'..'Z'}:
res.add toUpperAscii(result)
else: