Just want to know the list of printing format using the fmt package's functions.
For example, like:
%v is use for print the value.
%T can print the type of value.
What else?
The list of format "verbs" is available in the documentation of the fmt package :
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
%% a literal percent sign; consumes no 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
%q a single-quoted character literal safely escaped with Go syntax.
%x base 16, with lower-case letters for a-f
%X base 16, with upper-case letters for A-F
%U Unicode format: U+1234; same as "U+%04X"
Floating-point and complex constituents:
%b decimalless scientific notation with exponent a power of two,
in the manner of strconv.FormatFloat with the 'b' format,
e.g. -123456p-78
%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, lower-case, two characters per byte
%X base 16, upper-case, two characters per byte
Pointer:
%p base 16 notation, with leading 0x
Other flags:
+ always print a sign for numeric values;
guarantee ASCII-only output for %q (%+q)
- 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);
write e.g. U+0078 'x' if the character is printable for %U (%#U).
' ' (space) leave a space for elided sign in numbers (% d);
put spaces between bytes printing strings or slices in hex (% x, % X)
0 pad with leading zeros rather than spaces
You can find out more, check this out http://golang.org/pkg/fmt/
and run
$ godoc -http=0.0.0.0:8080
browser open localhost:8080 to get entire offline go website (also including your go src & doc)
Related
Is there a way to use scientific notation in objective c and have it display three significant digits only? What I am current using is:
string = [NSString stringWithFormat:#"%e", floatNumber];
// floatNumber = 100000; string = 1.000000e+06
I just want string = 1.00e+06
Use the format specifier ".2" as follows:
string = [NSString stringWithFormat:#"%.2e", floatNumber];
From apple's documentation:
The format specifiers supported by the NSString formatting methods and CFString formatting functions follow the IEEE printf specification...
And from the IEEE printf specification, if you read under the Description section, you will find:
e, E
The double argument shall be converted in the style "[-]d.ddde±dd", where there is one digit before the radix character (which is non-zero if the argument is non-zero) and the number of digits after it is equal to the precision; if the precision is missing, it shall be taken as 6; if the precision is zero and no '#' flag is present, no radix character shall appear. The low-order digit shall be rounded in an implementation-defined manner. The E conversion specifier shall produce a number with 'E' instead of 'e' introducing the exponent. The exponent shall always contain at least two digits. If the value is zero, the exponent shall be zero.
Is there a custom or standard library that I can use with objective c to convert a decimal floating point value into Hexadecimal, Binary and Octal NSStrings?
I've been looking around a lot but can only find how to convert the other direction (from everything else into decimal), by using: double result = (double)strtoll(myHexString.UTF8String, NULL,16)
As for octal and hex, you can exploit the fact that you can format numbers in hex and octal using the %x and %o specifiers:
NSString* str=[NSString stringWithFormat: #"Hex: %x Octal: %o",14,14];
But this only for the integral part, so you can use integers.If you want also the decimal part, to obtain fixed points you need to implement the algorithm, same for binary.
In order to complement the previous answer, the format specifier %x allows to treat integer value only.
If you get a decimal value greater than the max integer value you can use long long to cast your double value by this way: NSString * hexString = [NSString stringWithFormat:#"%llx", (long long)doubleValue];
I have a situation where I have lots of different double values, for example 1.00, 0.25 and 2.50. I would like to round these doubles so that they become 1, 0.25 and 2.5; in other words I want to remove any trailing 0's. Is there a way to do this?
At the moment I have been using %.2f, and I'm wondering if I can make use of this but adapt it in some way. Please can someone help me out?
As long as you're talking only about display, this is quite easy. The format specifier you want is %g:
The double argument shall be converted in the style f or e (or in the style F or E in the case of a G conversion specifier), with the precision specifying the number of significant digits [...] Trailing zeros shall be removed from the fractional portion of the result[...]
double twopointfive = 2.500;
double onepointzero = 1.0;
double pointtwofive = .25000000000;
NSLog(#"%g %f", twopointfive, twopointfive);
NSLog(#"%g %f", onepointzero, onepointzero);
NSLog(#"%g %f", pointtwofive, pointtwofive);
2011-12-06 21:27:59.180 TrailingZeroes[39506:903] 2.5 2.500000
2011-12-06 21:27:59.184 TrailingZeroes[39506:903] 1 1.000000
2011-12-06 21:27:59.185 TrailingZeroes[39506:903] 0.25 0.250000
The same format specifier can be used with an NSNumberFormatter, which will also give you some control over significant digits.
The trailing zeroes can't be removed from the way the number is stored in memory, of course.
I believe you want the %g format specifier to redact trailing zeros.
Not really rounding, but have you tried just %f it should only show the number of digits required rather then padding out the number.
My answer above is wrong, %g as others has stated is the right way to go.
The documentation for string formatters should help too. http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265
Here is a list of all the format specifiers that you can use...
%# Object
%d, %i signed int
%u unsigned int
%f float/double
%x, %X hexadecimal int
%o octal int
%zu size_t
%p pointer
%e float/double (in scientific notation)
%g float/double (as %f or %e, depending on value)
%s C string (bytes)
%S C string (unichar)
%.*s Pascal string (requires two arguments, pass pstr[0] as the first, pstr+1 as the second)
%c character
%C unichar
%lld long long
%llu unsigned long long
%Lf long double
I'm reading someone elses code and they are using %#-1 to format an integer. I can't find anything on Google since it ignores symbols. Anyone else had more experience at string formatting than me?
[NSString stringWithFormat:#"%#-1", subnumber]
Thanks!
According to the specification:
Each conversion specification is introduced by the '%' character, or by the character sequence "%n$", after which the following appear in sequence:
Zero or more flags (in any order), which modify the meaning of the conversion specification.
An optional minimum field width. If the converted value has fewer bytes than the field width, it shall be padded with spaces by default on the left; it shall be padded on the right if the left-adjustment flag ( '-' ), described below, is given to the field width. The field width takes the form of an asterisk ( '*' ), described below, or a decimal integer.
An optional precision that gives the minimum number of digits to appear for the d, i, o, u, x, and X conversion specifiers; the number of digits to appear after the radix character for the a, A, e, E, f, and F conversion specifiers; the maximum number of significant digits for the g and G conversion specifiers; or the maximum number of bytes to be printed from a string in the s [XSI] [Option Start] and S [Option End] conversion specifiers. The precision takes the form of a period ( '.' ) followed either by an asterisk ( '*' ), described below, or an optional decimal digit string, where a null digit string is treated as zero. If a precision appears with any other conversion specifier, the behavior is undefined.
An optional length modifier that specifies the size of the argument.
A conversion specifier character that indicates the type of conversion to be applied.
We're using a conversion of the first type, since there's no dollar sign in here. Note the words in sequence at the top of the above list. The # is a conversion specifier character (as mentioned here), which indicates that we should access the value passed in as an NSObject and read its description property. Since we've already reached the last bullet point, the format code actually ends after the # symbol, and as #Kevin Ballard pointed out, the -1 is parsed as literal text.
That's just going to print "NUM-1" (where NUM is the number). To give an example, if the number is 5, that will print "5-1".
When using format strings, any modifiers to the format token must occur before the format type specifier. In this case, that means any modifiers to the %# token must occur between the % and the # (though I'm not sure if there are actually any modifiers that %# accepts).
subnumber is probably object of class like NSNumber. Like we use %d for int, %f for float, %# is place holder for a refrence. In that case
NSNumber *subnumber = [NSNumber numberWithInt:5];
NSLog([NSString stringWithFormat:#"%#-1", subnumber]);
will print '5-1'
I would like a regular expression to find the %s in the source string that don't form the start of a valid two-hex-digit escaped character (defined as a % followed by exactly two hexadecimal digits, upper or lower case) that can be used to replace only these % symbols with %25.
(The motivation is to make the best guess attempt to create legally escaped strings from strings of various origins that may be legally percent escaped and may not, and may even be a mixture of the two, without damaging the data intent if the original string was already correctly encoded, e.g. by blanket re-encoding).
Here's an example input string.
He%20has%20a%2050%%20chance%20of%20living%2C%20but%20there%27s%20only%20a%2025%%20chance%20of%20that.
This doesn't conform to any encoding standard because it is a mix of valid escaped characters eg. %20 and two loose percentage symbols. I'd like to convert those %s to %25s.
My progress so far is to identify a regex %[0-9a-z]{2} that finds the % symbols that are legal but I can't work out how to modify it to find the ones that aren't legal.
%(?![0-9a-fA-F]{2})
Should do the trick. Use a look-ahead to find a % NOT followed by a valid two-digit hexadecimal value then replace the found % symbol with your %25 replacement.
(Hopefully this works with (presumably) NSRegularExpression, or whatever you're using)
%(?![a-fA-F0-9]{2})
That's a percent followed by a negative lookahead for two hex digits.