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fmt: scan new number syntax
This CL updates fmt's scanner to accept the new number syntaxes: - Hexadecimal floating-point values. - Digit-separating underscores. - Leading 0b and 0o prefixes. See golang.org/design/19308-number-literals for background. For #12711. For #19308. For #28493. For #29008. Change-Id: I5582af5c94059c781e6cf4e862441d3df3006adf Reviewed-on: https://go-review.googlesource.com/c/160247 Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Russ Cox
parent
ac51237aff
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f601d412ce
@ -286,10 +286,10 @@
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For example, %x will scan an integer as a hexadecimal number,
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and %v will scan the default representation format for the value.
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The Printf verbs %p and %T and the flags # and + are not implemented.
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The verbs %e %E %f %F %g and %G are all equivalent and scan any
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floating-point or complex value. For float and complex literals in
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scientific notation, both the decimal (e) and binary (p) exponent
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formats are supported (for example: "2.3e+7" and "4.5p-8").
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For floating-point and complex values, all valid formatting verbs
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(%b %e %E %f %F %g %G %x %X and %v) are equivalent and accept
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both decimal and hexadecimal notation (for example: "2.3e+7", "0x4.5p-8")
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and digit-separating underscores (for example: "3.14159_26535_89793").
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Input processed by verbs is implicitly space-delimited: the
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implementation of every verb except %c starts by discarding
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@ -297,9 +297,10 @@
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(and %v reading into a string) stops consuming input at the first
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space or newline character.
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The familiar base-setting prefixes 0 (octal) and 0x
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(hexadecimal) are accepted when scanning integers without
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a format or with the %v verb.
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The familiar base-setting prefixes 0b (binary), 0o and 0 (octal),
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and 0x (hexadecimal) are accepted when scanning integers
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without a format or with the %v verb, as are digit-separating
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underscores.
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Width is interpreted in the input text but there is no
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syntax for scanning with a precision (no %5.2f, just %5f).
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@ -562,7 +562,7 @@ const (
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hexadecimalDigits = "0123456789aAbBcCdDeEfF"
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sign = "+-"
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period = "."
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exponent = "eEp"
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exponent = "eEpP"
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)
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// getBase returns the numeric base represented by the verb and its digit string.
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@ -609,20 +609,26 @@ func (s *ss) scanRune(bitSize int) int64 {
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return r
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}
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// scanBasePrefix reports whether the integer begins with a 0 or 0x,
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// scanBasePrefix reports whether the integer begins with a bas prefix
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// and returns the base, digit string, and whether a zero was found.
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// It is called only if the verb is %v.
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func (s *ss) scanBasePrefix() (base int, digits string, found bool) {
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if !s.peek("0") {
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return 10, decimalDigits, false
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return 0, decimalDigits + "_", false
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}
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s.accept("0")
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found = true // We've put a digit into the token buffer.
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// Special cases for '0' && '0x'
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base, digits = 8, octalDigits
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if s.peek("xX") {
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s.consume("xX", false)
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base, digits = 16, hexadecimalDigits
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// Special cases for 0, 0b, 0o, 0x.
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base, digits = 0, octalDigits+"_"
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if s.peek("bB") {
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s.consume("bB", true)
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base, digits = 0, binaryDigits+"_"
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} else if s.peek("oO") {
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s.consume("oO", true)
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base, digits = 0, octalDigits+"_"
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} else if s.peek("xX") {
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s.consume("xX", true)
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base, digits = 0, hexadecimalDigits+"_"
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}
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return
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}
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@ -705,21 +711,27 @@ func (s *ss) floatToken() string {
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if s.accept("iI") && s.accept("nN") && s.accept("fF") {
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return string(s.buf)
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}
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digits := decimalDigits + "_"
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exp := exponent
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if s.accept("0") && s.accept("xX") {
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digits = hexadecimalDigits + "_"
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exp = "pP"
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}
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// digits?
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for s.accept(decimalDigits) {
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for s.accept(digits) {
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}
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// decimal point?
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if s.accept(period) {
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// fraction?
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for s.accept(decimalDigits) {
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for s.accept(digits) {
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}
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}
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// exponent?
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if s.accept(exponent) {
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if s.accept(exp) {
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// leading sign?
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s.accept(sign)
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// digits?
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for s.accept(decimalDigits) {
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for s.accept(decimalDigits + "_") {
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}
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}
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return string(s.buf)
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@ -749,9 +761,21 @@ func (s *ss) complexTokens() (real, imag string) {
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return real, imagSign + imag
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}
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func hasX(s string) bool {
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for i := 0; i < len(s); i++ {
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if s[i] == 'x' || s[i] == 'X' {
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return true
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}
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}
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return false
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}
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// convertFloat converts the string to a float64value.
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func (s *ss) convertFloat(str string, n int) float64 {
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if p := indexRune(str, 'p'); p >= 0 {
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// strconv.ParseFloat will handle "+0x1.fp+2",
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// but we have to implement our non-standard
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// decimal+binary exponent mix (1.2p4) ourselves.
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if p := indexRune(str, 'p'); p >= 0 && !hasX(str) {
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// Atof doesn't handle power-of-2 exponents,
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// but they're easy to evaluate.
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f, err := strconv.ParseFloat(str[:p], n)
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@ -124,12 +124,18 @@ var scanTests = []ScanTest{
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{"T\n", &boolVal, true}, // boolean test vals toggle to be sure they are written
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{"F\n", &boolVal, false}, // restored to zero value
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{"21\n", &intVal, 21},
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{"2_1\n", &intVal, 21},
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{"0\n", &intVal, 0},
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{"000\n", &intVal, 0},
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{"0x10\n", &intVal, 0x10},
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{"0x_1_0\n", &intVal, 0x10},
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{"-0x10\n", &intVal, -0x10},
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{"0377\n", &intVal, 0377},
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{"0_3_7_7\n", &intVal, 0377},
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{"0o377\n", &intVal, 0377},
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{"0o_3_7_7\n", &intVal, 0377},
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{"-0377\n", &intVal, -0377},
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{"-0o377\n", &intVal, -0377},
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{"0\n", &uintVal, uint(0)},
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{"000\n", &uintVal, uint(0)},
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{"0x10\n", &uintVal, uint(0x10)},
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@ -163,13 +169,20 @@ var scanTests = []ScanTest{
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{"2.3e2\n", &float64Val, 2.3e2},
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{"2.3p2\n", &float64Val, 2.3 * 4},
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{"2.3p+2\n", &float64Val, 2.3 * 4},
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{"2.3p+66\n", &float64Val, 2.3 * (1 << 32) * (1 << 32) * 4},
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{"2.3p-66\n", &float64Val, 2.3 / ((1 << 32) * (1 << 32) * 4)},
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{"2.3p+66\n", &float64Val, 2.3 * (1 << 66)},
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{"2.3p-66\n", &float64Val, 2.3 / (1 << 66)},
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{"0x2.3p-66\n", &float64Val, float64(0x23) / (1 << 70)},
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{"2_3.4_5\n", &float64Val, 23.45},
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{"2.35\n", &stringVal, "2.35"},
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{"2345678\n", &bytesVal, []byte("2345678")},
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{"(3.4e1-2i)\n", &complex128Val, 3.4e1 - 2i},
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{"-3.45e1-3i\n", &complex64Val, complex64(-3.45e1 - 3i)},
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{"-.45e1-1e2i\n", &complex128Val, complex128(-.45e1 - 100i)},
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{"-.4_5e1-1E2i\n", &complex128Val, complex128(-.45e1 - 100i)},
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{"0x1.0p1+0x1.0P2i\n", &complex128Val, complex128(2 + 4i)},
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{"-0x1p1-0x1p2i\n", &complex128Val, complex128(-2 - 4i)},
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{"-0x1ep-1-0x1p2i\n", &complex128Val, complex128(-15 - 4i)},
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{"-0x1_Ep-1-0x1p0_2i\n", &complex128Val, complex128(-15 - 4i)},
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{"hello\n", &stringVal, "hello"},
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// Carriage-return followed by newline. (We treat \r\n as \n always.)
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@ -207,8 +220,15 @@ var scanfTests = []ScanfTest{
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{"%v", "TRUE\n", &boolVal, true},
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{"%t", "false\n", &boolVal, false},
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{"%v", "-71\n", &intVal, -71},
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{"%v", "-7_1\n", &intVal, -71},
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{"%v", "0b111\n", &intVal, 7},
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{"%v", "0b_1_1_1\n", &intVal, 7},
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{"%v", "0377\n", &intVal, 0377},
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{"%v", "0_3_7_7\n", &intVal, 0377},
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{"%v", "0o377\n", &intVal, 0377},
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{"%v", "0o_3_7_7\n", &intVal, 0377},
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{"%v", "0x44\n", &intVal, 0x44},
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{"%v", "0x_4_4\n", &intVal, 0x44},
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{"%d", "72\n", &intVal, 72},
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{"%c", "a\n", &runeVal, 'a'},
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{"%c", "\u5072\n", &runeVal, '\u5072'},
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@ -222,17 +242,31 @@ var scanfTests = []ScanfTest{
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{"%x", "a75\n", &intVal, 0xa75},
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{"%v", "71\n", &uintVal, uint(71)},
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{"%d", "72\n", &uintVal, uint(72)},
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{"%d", "7_2\n", &uintVal, uint(7)}, // only %v takes underscores
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{"%d", "73\n", &uint8Val, uint8(73)},
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{"%d", "74\n", &uint16Val, uint16(74)},
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{"%d", "75\n", &uint32Val, uint32(75)},
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{"%d", "76\n", &uint64Val, uint64(76)},
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{"%b", "1001001\n", &uintVal, uint(73)},
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{"%b", "100_1001\n", &uintVal, uint(4)},
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{"%o", "075\n", &uintVal, uint(075)},
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{"%o", "07_5\n", &uintVal, uint(07)}, // only %v takes underscores
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{"%x", "a75\n", &uintVal, uint(0xa75)},
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{"%x", "A75\n", &uintVal, uint(0xa75)},
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{"%x", "A7_5\n", &uintVal, uint(0xa7)}, // only %v takes underscores
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{"%U", "U+1234\n", &intVal, int(0x1234)},
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{"%U", "U+4567\n", &uintVal, uint(0x4567)},
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{"%e", "2.3\n", &float64Val, 2.3},
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{"%E", "2.3e1\n", &float32Val, float32(2.3e1)},
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{"%f", "2.3e2\n", &float64Val, 2.3e2},
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{"%g", "2.3p2\n", &float64Val, 2.3 * 4},
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{"%G", "2.3p+2\n", &float64Val, 2.3 * 4},
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{"%v", "2.3p+66\n", &float64Val, 2.3 * (1 << 66)},
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{"%f", "2.3p-66\n", &float64Val, 2.3 / (1 << 66)},
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{"%G", "0x2.3p-66\n", &float64Val, float64(0x23) / (1 << 70)},
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{"%E", "2_3.4_5\n", &float64Val, 23.45},
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// Strings
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{"%s", "using-%s\n", &stringVal, "using-%s"},
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{"%x", "7573696e672d2578\n", &stringVal, "using-%x"},
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