--- /dev/null
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+ Package fmt implements formatted I/O with functions analogous
+ to C's printf and scanf. The format 'verbs' are derived from C's but
+ are simpler.
+
+ Printing:
+
+ The verbs:
+
+ General:
+ %v the value in a default format.
+ when printing structs, the plus flag (%+v) adds field names
+ %#v a Go-syntax representation of the value
+ %T a Go-syntax representation of the type of the value
+
+ Boolean:
+ %t the word true or false
+ Integer:
+ %b base 2
+ %c the character represented by the corresponding Unicode code point
+ %d base 10
+ %o base 8
+ %x base 16, with lower-case letters for a-f
+ %X base 16, with upper-case letters for A-F
+ Floating-point and complex constituents:
+ %e scientific notation, e.g. -1234.456e+78
+ %E scientific notation, e.g. -1234.456E+78
+ %f decimal point but no exponent, e.g. 123.456
+ %g whichever of %e or %f produces more compact output
+ %G whichever of %E or %f produces more compact output
+ String and slice of bytes:
+ %s the uninterpreted bytes of the string or slice
+ %q a double-quoted string safely escaped with Go syntax
+ %x base 16 notation with two characters per byte
+ Pointer:
+ %p base 16 notation, with leading 0x
+
+ There is no 'u' flag. Integers are printed unsigned if they have unsigned type.
+ Similarly, there is no need to specify the size of the operand (int8, int64).
+
+ For numeric values, the width and precision flags control
+ formatting; width sets the width of the field, precision the
+ number of places after the decimal, if appropriate. The
+ format %6.2f prints 123.45. The width of a field is the number
+ of Unicode code points in the string. This differs from C's printf where
+ the field width is the number of bytes.
+
+ Other flags:
+ + always print a sign for numeric values
+ - pad with spaces on the right rather than the left (left-justify the field)
+ # alternate format: add leading 0 for octal (%#o), 0x for hex (%#x);
+ 0X for hex (%#X); suppress 0x for %p (%#p);
+ print a raw (backquoted) string if possible for %q (%#q)
+ ' ' (space) leave a space for elided sign in numbers (% d);
+ put spaces between bytes printing strings or slices in hex (% x)
+ 0 pad with leading zeros rather than spaces
+
+ For each Printf-like function, there is also a Print function
+ that takes no format and is equivalent to saying %v for every
+ operand. Another variant Println inserts blanks between
+ operands and appends a newline.
+
+ Regardless of the verb, if an operand is an interface value,
+ the internal concrete value is used, not the interface itself.
+ Thus:
+ var i interface{} = 23;
+ fmt.Printf("%v\n", i);
+ will print 23.
+
+ If an operand implements interface Formatter, that interface
+ can be used for fine control of formatting.
+
+ If an operand implements method String() string that method
+ will be used to conver the object to a string, which will then
+ be formatted as required by the verb (if any). To avoid
+ recursion in cases such as
+ type X int
+ func (x X) String() string { return Sprintf("%d", x) }
+ cast the value before recurring:
+ func (x X) String() string { return Sprintf("%d", int(x)) }
+
+ Scanning:
+
+ An analogous set of functions scans formatted text to yield
+ values. Scan, Scanf and Scanln read from os.Stdin; Fscan,
+ Fscanf and Fscanln read from a specified os.Reader; Sscan,
+ Sscanf and Sscanln read from an argument string. Sscanln,
+ Fscanln and Sscanln stop scanning at a newline and require that
+ the items be followed by one; Sscanf, Fscanf and Sscanf require
+ newlines in the input to match newlines in the format; the other
+ routines treat newlines as spaces.
+
+ Scanf, Fscanf, and Sscanf parse the arguments according to a
+ format string, analogous to that of Printf. For example, "%x"
+ will scan an integer as a hexadecimal number, and %v will scan
+ the default representation format for the value.
+
+ The formats behave analogously to those of Printf with the
+ following exceptions:
+
+ %p is not implemented
+ %T is not implemented
+ %e %E %f %F %g %g are all equivalent and scan any floating
+ point or complex value
+ %s and %v on strings scan a space-delimited token
+
+ Width is interpreted in the input text (%5s means at most
+ five runes of input will be read to scan a string) but there
+ is no syntax for scanning with a precision (no %5.2f, just
+ %5f).
+
+ When scanning with a format, all non-empty runs of space
+ characters (except newline) are equivalent to a single
+ space in both the format and the input. With that proviso,
+ text in the format string must match the input text; scanning
+ stops if it does not, with the return value of the function
+ indicating the number of arguments scanned.
+
+ In all the scanning functions, if an operand implements method
+ Scan (that is, it implements the Scanner interface) that
+ method will be used to scan the text for that operand. Also,
+ if the number of arguments scanned is less than the number of
+ arguments provided, an error is returned.
+
+ All arguments to be scanned must be either pointers to basic
+ types or implementations of the Scanner interface.
+*/
+package fmt
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
-/*
- Package fmt implements formatted I/O with functions analogous
- to C's printf and scanf. The format 'verbs' are derived from C's but
- are simpler.
-
- Printing:
-
- The verbs:
-
- General:
- %v the value in a default format.
- when printing structs, the plus flag (%+v) adds field names
- %#v a Go-syntax representation of the value
- %T a Go-syntax representation of the type of the value
-
- Boolean:
- %t the word true or false
- Integer:
- %b base 2
- %c the character represented by the corresponding Unicode code point
- %d base 10
- %o base 8
- %x base 16, with lower-case letters for a-f
- %X base 16, with upper-case letters for A-F
- Floating-point and complex constituents:
- %e scientific notation, e.g. -1234.456e+78
- %E scientific notation, e.g. -1234.456E+78
- %f decimal point but no exponent, e.g. 123.456
- %g whichever of %e or %f produces more compact output
- %G whichever of %E or %f produces more compact output
- String and slice of bytes:
- %s the uninterpreted bytes of the string or slice
- %q a double-quoted string safely escaped with Go syntax
- %x base 16 notation with two characters per byte
- Pointer:
- %p base 16 notation, with leading 0x
-
- There is no 'u' flag. Integers are printed unsigned if they have unsigned type.
- Similarly, there is no need to specify the size of the operand (int8, int64).
-
- For numeric values, the width and precision flags control
- formatting; width sets the width of the field, precision the
- number of places after the decimal, if appropriate. The
- format %6.2f prints 123.45. The width of a field is the number
- of Unicode code points in the string. This differs from C's printf where
- the field width is the number of bytes.
-
- Other flags:
- + always print a sign for numeric values
- - pad with spaces on the right rather than the left (left-justify the field)
- # alternate format: add leading 0 for octal (%#o), 0x for hex (%#x);
- 0X for hex (%#X); suppress 0x for %p (%#p);
- print a raw (backquoted) string if possible for %q (%#q)
- ' ' (space) leave a space for elided sign in numbers (% d);
- put spaces between bytes printing strings or slices in hex (% x)
- 0 pad with leading zeros rather than spaces
-
- For each Printf-like function, there is also a Print function
- that takes no format and is equivalent to saying %v for every
- operand. Another variant Println inserts blanks between
- operands and appends a newline.
-
- Regardless of the verb, if an operand is an interface value,
- the internal concrete value is used, not the interface itself.
- Thus:
- var i interface{} = 23;
- fmt.Printf("%v\n", i);
- will print 23.
-
- If an operand implements interface Formatter, that interface
- can be used for fine control of formatting.
-
- If an operand implements method String() string that method
- will be used to conver the object to a string, which will then
- be formatted as required by the verb (if any). To avoid
- recursion in cases such as
- type X int
- func (x X) String() string { return Sprintf("%d", x) }
- cast the value before recurring:
- func (x X) String() string { return Sprintf("%d", int(x)) }
-
- Scanning:
-
- An analogous set of functions scans formatted text to yield
- values. Scan, Scanf and Scanln read from os.Stdin; Fscan,
- Fscanf and Fscanln read from a specified os.Reader; Sscan,
- Sscanf and Sscanln read from an argument string. Sscanln,
- Fscanln and Sscanln stop scanning at a newline and require that
- the items be followed by one; the other routines treat newlines
- as spaces.
-
- Scanf, Fscanf, and Sscanf parse the arguments according to a
- format string, analogous to that of Printf. For example, "%x"
- will scan an integer as a hexadecimal number, and %v will scan
- the default representation format for the value.
-
- The formats behave analogously to those of Printf with the
- following exceptions:
-
- %p is not implemented
- %T is not implemented
- %e %E %f %F %g %g are all equivalent and scan any floating
- point or complex value
- %s and %v on strings scan a space-delimited token
-
- Width is interpreted in the input text (%5s means at most
- five runes of input will be read to scan a string) but there
- is no syntax for scanning with a precision (no %5.2f, just
- %5f).
-
- When scanning with a format, all non-empty runs of space
- characters (including newline) are equivalent to a single
- space in both the format and the input. With that proviso,
- text in the format string must match the input text; scanning
- stops if it does not, with the return value of the function
- indicating the number of arguments scanned.
-
- In all the scanning functions, if an operand implements method
- Scan (that is, it implements the Scanner interface) that
- method will be used to scan the text for that operand. Also,
- if the number of arguments scanned is less than the number of
- arguments provided, an error is returned.
-
- All arguments to be scanned must be either pointers to basic
- types or implementations of the Scanner interface.
-*/
package fmt
import (