Involved Source Filesatob.goatoc.goatof.goatoi.gobytealg.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.goftoa.goftoaryu.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)
// fmt.Println uses these arguments to print floats
fmt64 := strconv.FormatFloat(v, 'g', -1, 64)
fmt.Printf("%T, %v\n", fmt64, fmt64)
}
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.QuotedPrefix("not a quoted string")
fmt.Printf("%q, %v\n", s, err)
s, err = strconv.QuotedPrefix("\"double-quoted string\" with trailing text")
fmt.Printf("%q, %v\n", s, err)
s, err = strconv.QuotedPrefix("`or backquoted` with more trailing text")
fmt.Printf("%q, %v\n", s, err)
s, err = strconv.QuotedPrefix("'\u263a' is also okay")
fmt.Printf("%q, %v\n", s, err)
}
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 (only one)
/* sort 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(*NumError) Error() string(*NumError) Unwrap() error
*NumError : error
Package-Level Functions (total 34)
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 numbers
as defined by the Go syntax for [floating-point literals].
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 string "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.
The string may begin with a leading sign: "+" or "-".
If the base argument is 0, the true base is implied by the string's
prefix following the sign (if present): 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.
A sign prefix is not permitted.
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.
QuotedPrefix returns the quoted string (as understood by Unquote) at the prefix of s.
If s does not start with a valid quoted string, QuotedPrefix returns an error.
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.
If r is not a valid Unicode code point, it is interpreted as the Unicode
replacement character U+FFFD.
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.
If r is not a valid Unicode code point, it is interpreted as the Unicode
replacement character U+FFFD.
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).
If r is not a valid Unicode code point, it is interpreted as the Unicode
replacement character U+FFFD.
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.
Package-Level Variables (total 2)
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.
Package-Level Constants (only one)
IntSize is the size in bits of an int or uint value.
The pages are generated with Goldsv0.6.9-preview. (GOOS=linux 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.
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