Involved Source Filesatob.goatoc.goatof.goatoi.goctoa.godecimal.go
Package strconv implements conversions to and from string representations
of basic data types.
Numeric Conversions
The most common numeric conversions are Atoi (string to int) and Itoa (int to string).
i, err := strconv.Atoi("-42")
s := strconv.Itoa(-42)
These assume decimal and the Go int type.
ParseBool, ParseFloat, ParseInt, and ParseUint convert strings to values:
b, err := strconv.ParseBool("true")
f, err := strconv.ParseFloat("3.1415", 64)
i, err := strconv.ParseInt("-42", 10, 64)
u, err := strconv.ParseUint("42", 10, 64)
The parse functions return the widest type (float64, int64, and uint64),
but if the size argument specifies a narrower width the result can be
converted to that narrower type without data loss:
s := "2147483647" // biggest int32
i64, err := strconv.ParseInt(s, 10, 32)
...
i := int32(i64)
FormatBool, FormatFloat, FormatInt, and FormatUint convert values to strings:
s := strconv.FormatBool(true)
s := strconv.FormatFloat(3.1415, 'E', -1, 64)
s := strconv.FormatInt(-42, 16)
s := strconv.FormatUint(42, 16)
AppendBool, AppendFloat, AppendInt, and AppendUint are similar but
append the formatted value to a destination slice.
String Conversions
Quote and QuoteToASCII convert strings to quoted Go string literals.
The latter guarantees that the result is an ASCII string, by escaping
any non-ASCII Unicode with \u:
q := strconv.Quote("Hello, 世界")
q := strconv.QuoteToASCII("Hello, 世界")
QuoteRune and QuoteRuneToASCII are similar but accept runes and
return quoted Go rune literals.
Unquote and UnquoteChar unquote Go string and rune literals.
eisel_lemire.goextfloat.goftoa.goisprint.goitoa.goquote.go
Code Examples
package main
import (
"fmt"
"strconv"
)
func main() {
b := []byte("bool:")
b = strconv.AppendBool(b, true)
fmt.Println(string(b))
}
package main
import (
"fmt"
"strconv"
)
func main() {
b32 := []byte("float32:")
b32 = strconv.AppendFloat(b32, 3.1415926535, 'E', -1, 32)
fmt.Println(string(b32))
b64 := []byte("float64:")
b64 = strconv.AppendFloat(b64, 3.1415926535, 'E', -1, 64)
fmt.Println(string(b64))
}
package main
import (
"fmt"
"strconv"
)
func main() {
b10 := []byte("int (base 10):")
b10 = strconv.AppendInt(b10, -42, 10)
fmt.Println(string(b10))
b16 := []byte("int (base 16):")
b16 = strconv.AppendInt(b16, -42, 16)
fmt.Println(string(b16))
}
package main
import (
"fmt"
"strconv"
)
func main() {
b := []byte("quote:")
b = strconv.AppendQuote(b, `"Fran & Freddie's Diner"`)
fmt.Println(string(b))
}
package main
import (
"fmt"
"strconv"
)
func main() {
b := []byte("rune:")
b = strconv.AppendQuoteRune(b, '☺')
fmt.Println(string(b))
}
package main
import (
"fmt"
"strconv"
)
func main() {
b := []byte("rune (ascii):")
b = strconv.AppendQuoteRuneToASCII(b, '☺')
fmt.Println(string(b))
}
package main
import (
"fmt"
"strconv"
)
func main() {
b := []byte("quote (ascii):")
b = strconv.AppendQuoteToASCII(b, `"Fran & Freddie's Diner"`)
fmt.Println(string(b))
}
package main
import (
"fmt"
"strconv"
)
func main() {
b10 := []byte("uint (base 10):")
b10 = strconv.AppendUint(b10, 42, 10)
fmt.Println(string(b10))
b16 := []byte("uint (base 16):")
b16 = strconv.AppendUint(b16, 42, 16)
fmt.Println(string(b16))
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := "10"
if s, err := strconv.Atoi(v); err == nil {
fmt.Printf("%T, %v", s, s)
}
}
package main
import (
"fmt"
"strconv"
)
func main() {
fmt.Println(strconv.CanBackquote("Fran & Freddie's Diner ☺"))
fmt.Println(strconv.CanBackquote("`can't backquote this`"))
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := true
s := strconv.FormatBool(v)
fmt.Printf("%T, %v\n", s, s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := 3.1415926535
s32 := strconv.FormatFloat(v, 'E', -1, 32)
fmt.Printf("%T, %v\n", s32, s32)
s64 := strconv.FormatFloat(v, 'E', -1, 64)
fmt.Printf("%T, %v\n", s64, s64)
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := int64(-42)
s10 := strconv.FormatInt(v, 10)
fmt.Printf("%T, %v\n", s10, s10)
s16 := strconv.FormatInt(v, 16)
fmt.Printf("%T, %v\n", s16, s16)
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := uint64(42)
s10 := strconv.FormatUint(v, 10)
fmt.Printf("%T, %v\n", s10, s10)
s16 := strconv.FormatUint(v, 16)
fmt.Printf("%T, %v\n", s16, s16)
}
package main
import (
"fmt"
"strconv"
)
func main() {
shamrock := strconv.IsGraphic('☘')
fmt.Println(shamrock)
a := strconv.IsGraphic('a')
fmt.Println(a)
bel := strconv.IsGraphic('\007')
fmt.Println(bel)
}
package main
import (
"fmt"
"strconv"
)
func main() {
c := strconv.IsPrint('\u263a')
fmt.Println(c)
bel := strconv.IsPrint('\007')
fmt.Println(bel)
}
package main
import (
"fmt"
"strconv"
)
func main() {
i := 10
s := strconv.Itoa(i)
fmt.Printf("%T, %v\n", s, s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
str := "Not a number"
if _, err := strconv.ParseFloat(str, 64); err != nil {
e := err.(*strconv.NumError)
fmt.Println("Func:", e.Func)
fmt.Println("Num:", e.Num)
fmt.Println("Err:", e.Err)
fmt.Println(err)
}
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := "true"
if s, err := strconv.ParseBool(v); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := "3.1415926535"
if s, err := strconv.ParseFloat(v, 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseFloat(v, 64); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseFloat("NaN", 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
// ParseFloat is case insensitive
if s, err := strconv.ParseFloat("nan", 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseFloat("inf", 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseFloat("+Inf", 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseFloat("-Inf", 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseFloat("-0", 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseFloat("+0", 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
}
package main
import (
"fmt"
"strconv"
)
func main() {
v32 := "-354634382"
if s, err := strconv.ParseInt(v32, 10, 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseInt(v32, 16, 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
v64 := "-3546343826724305832"
if s, err := strconv.ParseInt(v64, 10, 64); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseInt(v64, 16, 64); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
}
package main
import (
"fmt"
"strconv"
)
func main() {
v := "42"
if s, err := strconv.ParseUint(v, 10, 32); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
if s, err := strconv.ParseUint(v, 10, 64); err == nil {
fmt.Printf("%T, %v\n", s, s)
}
}
package main
import (
"fmt"
"strconv"
)
func main() {
// This string literal contains a tab character.
s := strconv.Quote(`"Fran & Freddie's Diner ☺"`)
fmt.Println(s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
s := strconv.QuoteRune('☺')
fmt.Println(s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
s := strconv.QuoteRuneToASCII('☺')
fmt.Println(s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
s := strconv.QuoteRuneToGraphic('☺')
fmt.Println(s)
s = strconv.QuoteRuneToGraphic('\u263a')
fmt.Println(s)
s = strconv.QuoteRuneToGraphic('\u000a')
fmt.Println(s)
s = strconv.QuoteRuneToGraphic(' ') // tab character
fmt.Println(s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
// This string literal contains a tab character.
s := strconv.QuoteToASCII(`"Fran & Freddie's Diner ☺"`)
fmt.Println(s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
s := strconv.QuoteToGraphic("☺")
fmt.Println(s)
// This string literal contains a tab character.
s = strconv.QuoteToGraphic("This is a \u263a \u000a")
fmt.Println(s)
s = strconv.QuoteToGraphic(`" This is a ☺ \n "`)
fmt.Println(s)
}
package main
import (
"fmt"
"strconv"
)
func main() {
s, err := strconv.Unquote("You can't unquote a string without quotes")
fmt.Printf("%q, %v\n", s, err)
s, err = strconv.Unquote("\"The string must be either double-quoted\"")
fmt.Printf("%q, %v\n", s, err)
s, err = strconv.Unquote("`or backquoted.`")
fmt.Printf("%q, %v\n", s, err)
s, err = strconv.Unquote("'\u263a'") // single character only allowed in single quotes
fmt.Printf("%q, %v\n", s, err)
s, err = strconv.Unquote("'\u2639\u2639'")
fmt.Printf("%q, %v\n", s, err)
}
package main
import (
"fmt"
"log"
"strconv"
)
func main() {
v, mb, t, err := strconv.UnquoteChar(`\"Fran & Freddie's Diner\"`, '"')
if err != nil {
log.Fatal(err)
}
fmt.Println("value:", string(v))
fmt.Println("multibyte:", mb)
fmt.Println("tail:", t)
}
Package-Level Type Names (total 6, in which 1 are exported)
/* sort exporteds by: | */
A NumError records a failed conversion.
// the reason the conversion failed (e.g. ErrRange, ErrSyntax, etc.)
// the failing function (ParseBool, ParseInt, ParseUint, ParseFloat, ParseComplex)
// the input
(*T) Error() string(*T) Unwrap() error
*T : error
func baseError(fn, str string, base int) *NumError
func bitSizeError(fn, str string, bitSize int) *NumError
func rangeError(fn, str string) *NumError
func syntaxError(fn, str string) *NumError
// digits, big-endian representation
// decimal point
// number of digits used
// negative flag
// discarded nonzero digits beyond d[:nd]
Assign v to a.
Round a to nd digits (or fewer).
If nd is zero, it means we're rounding
just to the left of the digits, as in
0.09 -> 0.1.
Round a down to nd digits (or fewer).
Round a up to nd digits (or fewer).
Extract integer part, rounded appropriately.
No guarantees about overflow.
Binary shift left (k > 0) or right (k < 0).
(*T) String() string(*T) floatBits(flt *floatInfo) (b uint64, overflow bool)(*T) set(s string) (ok bool)
*T : fmt.Stringer
*T : context.stringer
*T : runtime.stringer
func leftShift(a *decimal, k uint)
func rightShift(a *decimal, k uint)
func roundShortest(d *decimal, mant uint64, exp int, flt *floatInfo)
func shouldRoundUp(a *decimal, nd int) bool
func trim(a *decimal)
An extFloat represents an extended floating-point number, with more
precision than a float64. It does not try to save bits: the
number represented by the structure is mant*(2^exp), with a negative
sign if neg is true.
expintmantuint64negbool
AssignComputeBounds sets f to the floating point value
defined by mant, exp and precision given by flt. It returns
lower, upper such that any number in the closed interval
[lower, upper] is converted back to the same floating point number.
FixedDecimal stores in d the first n significant digits
of the decimal representation of f. It returns false
if it cannot be sure of the answer.
Multiply sets f to the product f*g: the result is correctly rounded,
but not normalized.
Normalize normalizes f so that the highest bit of the mantissa is
set, and returns the number by which the mantissa was left-shifted.
ShortestDecimal stores in d the shortest decimal representation of f
which belongs to the open interval (lower, upper), where f is supposed
to lie. It returns false whenever the result is unsure. The implementation
uses the Grisu3 algorithm.
Frexp10 is an analogue of math.Frexp for decimal powers. It scales
f by an approximate power of ten 10^-exp, and returns exp10, so
that f*10^exp10 has the same value as the old f, up to an ulp,
as well as the index of 10^-exp in the powersOfTen table.
func frexp10Many(a, b, c *extFloat) (exp10 int)
// minus one digit if original < a.
// number of new digits
Package-Level Functions (total 83, in which 33 are exported)
AppendBool appends "true" or "false", according to the value of b,
to dst and returns the extended buffer.
AppendFloat appends the string form of the floating-point number f,
as generated by FormatFloat, to dst and returns the extended buffer.
AppendInt appends the string form of the integer i,
as generated by FormatInt, to dst and returns the extended buffer.
AppendQuote appends a double-quoted Go string literal representing s,
as generated by Quote, to dst and returns the extended buffer.
AppendQuoteRune appends a single-quoted Go character literal representing the rune,
as generated by QuoteRune, to dst and returns the extended buffer.
AppendQuoteRuneToASCII appends a single-quoted Go character literal representing the rune,
as generated by QuoteRuneToASCII, to dst and returns the extended buffer.
AppendQuoteRuneToGraphic appends a single-quoted Go character literal representing the rune,
as generated by QuoteRuneToGraphic, to dst and returns the extended buffer.
AppendQuoteToASCII appends a double-quoted Go string literal representing s,
as generated by QuoteToASCII, to dst and returns the extended buffer.
AppendQuoteToGraphic appends a double-quoted Go string literal representing s,
as generated by QuoteToGraphic, to dst and returns the extended buffer.
AppendUint appends the string form of the unsigned integer i,
as generated by FormatUint, to dst and returns the extended buffer.
Atoi is equivalent to ParseInt(s, 10, 0), converted to type int.
CanBackquote reports whether the string s can be represented
unchanged as a single-line backquoted string without control
characters other than tab.
FormatBool returns "true" or "false" according to the value of b.
FormatComplex converts the complex number c to a string of the
form (a+bi) where a and b are the real and imaginary parts,
formatted according to the format fmt and precision prec.
The format fmt and precision prec have the same meaning as in FormatFloat.
It rounds the result assuming that the original was obtained from a complex
value of bitSize bits, which must be 64 for complex64 and 128 for complex128.
FormatFloat converts the floating-point number f to a string,
according to the format fmt and precision prec. It rounds the
result assuming that the original was obtained from a floating-point
value of bitSize bits (32 for float32, 64 for float64).
The format fmt is one of
'b' (-ddddp±ddd, a binary exponent),
'e' (-d.dddde±dd, a decimal exponent),
'E' (-d.ddddE±dd, a decimal exponent),
'f' (-ddd.dddd, no exponent),
'g' ('e' for large exponents, 'f' otherwise),
'G' ('E' for large exponents, 'f' otherwise),
'x' (-0xd.ddddp±ddd, a hexadecimal fraction and binary exponent), or
'X' (-0Xd.ddddP±ddd, a hexadecimal fraction and binary exponent).
The precision prec controls the number of digits (excluding the exponent)
printed by the 'e', 'E', 'f', 'g', 'G', 'x', and 'X' formats.
For 'e', 'E', 'f', 'x', and 'X', it is the number of digits after the decimal point.
For 'g' and 'G' it is the maximum number of significant digits (trailing
zeros are removed).
The special precision -1 uses the smallest number of digits
necessary such that ParseFloat will return f exactly.
FormatInt returns the string representation of i in the given base,
for 2 <= base <= 36. The result uses the lower-case letters 'a' to 'z'
for digit values >= 10.
FormatUint returns the string representation of i in the given base,
for 2 <= base <= 36. The result uses the lower-case letters 'a' to 'z'
for digit values >= 10.
IsGraphic reports whether the rune is defined as a Graphic by Unicode. Such
characters include letters, marks, numbers, punctuation, symbols, and
spaces, from categories L, M, N, P, S, and Zs.
IsPrint reports whether the rune is defined as printable by Go, with
the same definition as unicode.IsPrint: letters, numbers, punctuation,
symbols and ASCII space.
Itoa is equivalent to FormatInt(int64(i), 10).
ParseBool returns the boolean value represented by the string.
It accepts 1, t, T, TRUE, true, True, 0, f, F, FALSE, false, False.
Any other value returns an error.
ParseComplex converts the string s to a complex number
with the precision specified by bitSize: 64 for complex64, or 128 for complex128.
When bitSize=64, the result still has type complex128, but it will be
convertible to complex64 without changing its value.
The number represented by s must be of the form N, Ni, or N±Ni, where N stands
for a floating-point number as recognized by ParseFloat, and i is the imaginary
component. If the second N is unsigned, a + sign is required between the two components
as indicated by the ±. If the second N is NaN, only a + sign is accepted.
The form may be parenthesized and cannot contain any spaces.
The resulting complex number consists of the two components converted by ParseFloat.
The errors that ParseComplex returns have concrete type *NumError
and include err.Num = s.
If s is not syntactically well-formed, ParseComplex returns err.Err = ErrSyntax.
If s is syntactically well-formed but either component is more than 1/2 ULP
away from the largest floating point number of the given component's size,
ParseComplex returns err.Err = ErrRange and c = ±Inf for the respective component.
ParseFloat converts the string s to a floating-point number
with the precision specified by bitSize: 32 for float32, or 64 for float64.
When bitSize=32, the result still has type float64, but it will be
convertible to float32 without changing its value.
ParseFloat accepts decimal and hexadecimal floating-point number syntax.
If s is well-formed and near a valid floating-point number,
ParseFloat returns the nearest floating-point number rounded
using IEEE754 unbiased rounding.
(Parsing a hexadecimal floating-point value only rounds when
there are more bits in the hexadecimal representation than
will fit in the mantissa.)
The errors that ParseFloat returns have concrete type *NumError
and include err.Num = s.
If s is not syntactically well-formed, ParseFloat returns err.Err = ErrSyntax.
If s is syntactically well-formed but is more than 1/2 ULP
away from the largest floating point number of the given size,
ParseFloat returns f = ±Inf, err.Err = ErrRange.
ParseFloat recognizes the strings "NaN", and the (possibly signed) strings "Inf" and "Infinity"
as their respective special floating point values. It ignores case when matching.
ParseInt interprets a string s in the given base (0, 2 to 36) and
bit size (0 to 64) and returns the corresponding value i.
If the base argument is 0, the true base is implied by the string's
prefix: 2 for "0b", 8 for "0" or "0o", 16 for "0x", and 10 otherwise.
Also, for argument base 0 only, underscore characters are permitted
as defined by the Go syntax for integer literals.
The bitSize argument specifies the integer type
that the result must fit into. Bit sizes 0, 8, 16, 32, and 64
correspond to int, int8, int16, int32, and int64.
If bitSize is below 0 or above 64, an error is returned.
The errors that ParseInt returns have concrete type *NumError
and include err.Num = s. If s is empty or contains invalid
digits, err.Err = ErrSyntax and the returned value is 0;
if the value corresponding to s cannot be represented by a
signed integer of the given size, err.Err = ErrRange and the
returned value is the maximum magnitude integer of the
appropriate bitSize and sign.
ParseUint is like ParseInt but for unsigned numbers.
Quote returns a double-quoted Go string literal representing s. The
returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
control characters and non-printable characters as defined by
IsPrint.
QuoteRune returns a single-quoted Go character literal representing the
rune. The returned string uses Go escape sequences (\t, \n, \xFF, \u0100)
for control characters and non-printable characters as defined by IsPrint.
QuoteRuneToASCII returns a single-quoted Go character literal representing
the rune. The returned string uses Go escape sequences (\t, \n, \xFF,
\u0100) for non-ASCII characters and non-printable characters as defined
by IsPrint.
QuoteRuneToGraphic returns a single-quoted Go character literal representing
the rune. If the rune is not a Unicode graphic character,
as defined by IsGraphic, the returned string will use a Go escape sequence
(\t, \n, \xFF, \u0100).
QuoteToASCII returns a double-quoted Go string literal representing s.
The returned string uses Go escape sequences (\t, \n, \xFF, \u0100) for
non-ASCII characters and non-printable characters as defined by IsPrint.
QuoteToGraphic returns a double-quoted Go string literal representing s.
The returned string leaves Unicode graphic characters, as defined by
IsGraphic, unchanged and uses Go escape sequences (\t, \n, \xFF, \u0100)
for non-graphic characters.
Unquote interprets s as a single-quoted, double-quoted,
or backquoted Go string literal, returning the string value
that s quotes. (If s is single-quoted, it would be a Go
character literal; Unquote returns the corresponding
one-character string.)
UnquoteChar decodes the first character or byte in the escaped string
or character literal represented by the string s.
It returns four values:
1) value, the decoded Unicode code point or byte value;
2) multibyte, a boolean indicating whether the decoded character requires a multibyte UTF-8 representation;
3) tail, the remainder of the string after the character; and
4) an error that will be nil if the character is syntactically valid.
The second argument, quote, specifies the type of literal being parsed
and therefore which escaped quote character is permitted.
If set to a single quote, it permits the sequence \' and disallows unescaped '.
If set to a double quote, it permits \" and disallows unescaped ".
If set to zero, it does not permit either escape and allows both quote characters to appear unescaped.
adjustLastDigit modifies d = x-currentDiff*ε, to get closest to
d = x-targetDiff*ε, without becoming smaller than x-maxDiff*ε.
It assumes that a decimal digit is worth ulpDecimal*ε, and that
all data is known with an error estimate of ulpBinary*ε.
adjustLastDigitFixed assumes d contains the representation of the integral part
of some number, whose fractional part is num / (den << shift). The numerator
num is only known up to an uncertainty of size ε, assumed to be less than
(den << shift)/2.
It will increase the last digit by one to account for correct rounding, typically
when the fractional part is greater than 1/2, and will return false if ε is such
that no correct answer can be given.
If possible to convert decimal representation to 64-bit float f exactly,
entirely in floating-point math, do so, avoiding the expense of decimalToFloatBits.
Three common cases:
value is exact integer
value is exact integer * exact power of ten
value is exact integer / exact power of ten
These all produce potentially inexact but correctly rounded answers.
atofHex converts the hex floating-point string s
to a rounded float32 or float64 value (depending on flt==&float32info or flt==&float64info)
and returns it as a float64.
The string s has already been parsed into a mantissa, exponent, and sign (neg==true for negative).
If trunc is true, trailing non-zero bits have been omitted from the mantissa.
bsearch16 returns the smallest i such that a[i] >= x.
If there is no such i, bsearch16 returns len(a).
bsearch32 returns the smallest i such that a[i] >= x.
If there is no such i, bsearch32 returns len(a).
commonPrefixLenIgnoreCase returns the length of the common
prefix of s and prefix, with the character case of s ignored.
The prefix argument must be all lower-case.
contains reports whether the string contains the byte c.
convErr splits an error returned by parseFloatPrefix
into a syntax or range error for ParseComplex.
%x: -0x1.yyyyyyyyp±ddd or -0x0p+0. (y is hex digit, d is decimal digit)
formatBits computes the string representation of u in the given base.
If neg is set, u is treated as negative int64 value. If append_ is
set, the string is appended to dst and the resulting byte slice is
returned as the first result value; otherwise the string is returned
as the second result value.
isInGraphicList reports whether the rune is in the isGraphic list. This separation
from IsGraphic allows quoteWith to avoid two calls to IsPrint.
Should be called only if IsPrint fails.
Binary shift left (* 2) by k bits. k <= maxShift to avoid overflow.
lower(c) is a lower-case letter if and only if
c is either that lower-case letter or the equivalent upper-case letter.
Instead of writing c == 'x' || c == 'X' one can write lower(c) == 'x'.
Note that lower of non-letters can produce other non-letters.
readFloat reads a decimal or hexadecimal mantissa and exponent from a float
string representation in s; the number may be followed by other characters.
readFloat reports the number of bytes consumed (i), and whether the number
is valid (ok).
Binary shift right (/ 2) by k bits. k <= maxShift to avoid overflow.
roundShortest rounds d (= mant * 2^exp) to the shortest number of digits
that will let the original floating point value be precisely reconstructed.
If we chop a at nd digits, should we round up?
small returns the string for an i with 0 <= i < nSmalls.
special returns the floating-point value for the special,
possibly signed floating-point representations inf, infinity,
and NaN. The result is ok if a prefix of s contains one
of these representations and n is the length of that prefix.
The character case is ignored.
trim trailing zeros from number.
(They are meaningless; the decimal point is tracked
independent of the number of digits.)
underscoreOK reports whether the underscores in s are allowed.
Checking them in this one function lets all the parsers skip over them simply.
Underscore must appear only between digits or between a base prefix and a digit.
Package-Level Variables (total 18, in which 2 are exported)
ErrRange indicates that a value is out of range for the target type.
ErrSyntax indicates that a value does not have the right syntax for the target type.
detailedPowersOfTen contains 128-bit mantissa approximations (rounded down)
to the powers of 10. For example:
- 1e43 ≈ (0xE596B7B0_C643C719 * (2 ** 79))
- 1e43 = (0xE596B7B0_C643C719_6D9CCD05_D0000000 * (2 ** 15))
The mantissas are explicitly listed. The exponents are implied by a linear
expression with slope 217706.0/65536.0 ≈ log(10)/log(2).
The table was generated by
https://github.com/google/wuffs/blob/ba3818cb6b473a2ed0b38ecfc07dbbd3a97e8ae7/script/print-mpb-powers-of-10.go
The pages are generated with Goldsv0.4.2. (GOOS=darwin GOARCH=amd64)
Golds is a Go 101 project developed by Tapir Liu.
PR and bug reports are welcome and can be submitted to the issue list.
Please follow @Go100and1 (reachable from the left QR code) to get the latest news of Golds.
