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[DOC] More on format specs (#5877)
* Update doc/format_specifications.rdoc Co-authored-by: Peter Zhu <peter@peterzhu.ca>
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Burdette Lamar
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@ -58,8 +58,7 @@ The links lead to the details and examples.
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- +a+ or +A+: Format +argument+ as hexadecimal floating-point number.
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See {Specifiers a and A}[rdoc-ref:format_specifications.rdoc@Specifiers+a+and+A].
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- +e+ or +E+: Format +argument+ in
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{scientific notation}[https://en.wikipedia.org/wiki/Scientific_notation].
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- +e+ or +E+: Format +argument+ in scientific notation.
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See {Specifiers e and E}[rdoc-ref:format_specifications.rdoc@Specifiers+e+and+E].
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- +f+: Format +argument+ as a decimal floating-point number.
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See {Specifier f}[rdoc-ref:format_specifications.rdoc@Specifier+f].
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@ -75,12 +74,13 @@ The links lead to the details and examples.
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- +s+: Format +argument+ as a string via <tt>argument.to_s</tt>.
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See {Specifier s}[rdoc-ref:format_specifications.rdoc@Specifier+s].
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- <tt>%</tt>: Format +argument+ (<tt>'%'</tt>) as a single percent character.
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See {Specifier %}[rdoc-ref:format_specifications.rdoc@Specifier+%].
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See {Specifier %}[rdoc-ref:format_specifications.rdoc@Specifier+-25].
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=== Flags
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The effect of a flag may vary greatly among type specifiers.
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These remarks are general in nature.
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See {type-specific details}[rdoc-ref:format_specifications.rdoc@Type+Specifier+Details+and+Examples].
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Multiple flags may be given with single type specifier;
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order does not matter.
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@ -145,15 +145,70 @@ In general, a width specifier determines the minimum width (in characters)
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of the formatted field:
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sprintf('%10d', 100) # => " 100"
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# Left-justify if negative.
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sprintf('%-10d', 100) # => "100 "
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# Ignore if too small.
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sprintf('%1d', 100) # => "100"
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=== Precision Specifier
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A precision specifier is a decimal point followed by zero or more
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decimal digits.
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For integer type specifiers, the precision specifies the minimum number of
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digits to be written. If the precision is shorter than the integer, the result is
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padded with leading zeros. There is no modification or truncation of the result
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if the integer is longer than the precision:
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sprintf('%.3d', 1) # => "001"
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sprintf('%.3d', 1000) # => "1000"
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# If the precision is 0 and the value is 0, nothing is written
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sprintf('%.d', 0) # => ""
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sprintf('%.0d', 0) # => ""
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For the +a+/+A+, +e+/+E+, +f+/+F+ specifiers, the precision specifies
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the number of digits after the decimal point to be written:
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sprintf('%.2f', 3.14159) # => "3.14"
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sprintf('%.10f', 3.14159) # => "3.1415900000"
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# With no precision specifier, defaults to 6-digit precision.
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sprintf('%f', 3.14159) # => "3.141590"
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For the +g+/+G+ specifiers, the precision specifies
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the number of significant digits to be written:
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sprintf('%.2g', 123.45) # => "1.2e+02"
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sprintf('%.3g', 123.45) # => "123"
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sprintf('%.10g', 123.45) # => "123.45"
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# With no precision specifier, defaults to 6 significant digits.
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sprintf('%g', 123.456789) # => "123.457"
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For the +s+, +p+ specifiers, the precision specifies
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the number of characters to write:
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sprintf('%s', Time.now) # => "2022-05-04 11:59:16 -0400"
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sprintf('%.10s', Time.now) # => "2022-05-04"
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=== Type Specifier Details and Examples
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==== Specifiers +a+ and +A+
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Format +argument+ as hexadecimal floating-point number:
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sprintf('%a', 3.14159) # => "0x1.921f9f01b866ep+1"
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sprintf('%a', -3.14159) # => "-0x1.921f9f01b866ep+1"
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sprintf('%a', 4096) # => "0x1p+12"
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sprintf('%a', -4096) # => "-0x1p+12"
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# Capital 'A' means that alphabetical characters are printed in upper case.
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sprintf('%A', 4096) # => "0X1P+12"
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sprintf('%A', -4096) # => "-0X1P+12"
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==== Specifiers +b+ and +B+
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The two specifiers +b+ and +B+ behave identically
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@ -163,34 +218,121 @@ Format +argument+ as a binary integer:
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sprintf('%b', 1) # => "1"
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sprintf('%b', 4) # => "100"
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# Prefix '..' for negative value.
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sprintf('%b', -4) # => "..100"
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Type-specific modifier:
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- '#' flag' (use alternate format):
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sprintf('%#b', 1) # => "0b1"
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sprintf('%#B', 1) # => "0B1"
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# Alternate format.
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sprintf('%#b', 4) # => "0b100"
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sprintf('%#B', 4) # => "0B100"
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==== Specifier +c+
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Format +argument+ as a single character:
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sprintf('%c', 'A') # => "A"
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sprintf('%c', 65) # => "A"
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==== Specifier +d+
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Format +argument+ as a decimal integer:
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sprintf('%d', 100) # => "100"
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sprintf('%d', -100) # => "-100"
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Flag <tt>'#'</tt> does not apply.
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==== Specifiers +e+ and +E+
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Format +argument+ in
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{scientific notation}[https://en.wikipedia.org/wiki/Scientific_notation]:
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sprintf('%e', 3.14159) # => "3.141590e+00"
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sprintf('%E', -3.14159) # => "-3.141590E+00"
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==== Specifier +f+
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Format +argument+ as a floating-point number:
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sprintf('%f', 3.14159) # => "3.141590"
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sprintf('%f', -3.14159) # => "-3.141590"
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Flag <tt>'#'</tt> does not apply.
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==== Specifiers +g+ and +G+
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Format +argument+ using exponential form (+e+/+E+ specifier)
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if the exponent is less than -4 or greater than or equal to the precision.
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Otherwise format +argument+ using floating-point form (+f+ specifier):
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sprintf('%g', 100) # => "100"
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sprintf('%g', 100.0) # => "100"
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sprintf('%g', 3.14159) # => "3.14159"
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sprintf('%g', 100000000000) # => "1e+11"
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sprintf('%g', 0.000000000001) # => "1e-12"
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# Capital 'G' means use capital 'E'.
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sprintf('%G', 100000000000) # => "1E+11"
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sprintf('%G', 0.000000000001) # => "1E-12"
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# Alternate format.
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sprintf('%#g', 100000000000) # => "1.00000e+11"
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sprintf('%#g', 0.000000000001) # => "1.00000e-12"
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sprintf('%#G', 100000000000) # => "1.00000E+11"
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sprintf('%#G', 0.000000000001) # => "1.00000E-12"
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==== Specifier +o+
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Format +argument+ as an octal integer.
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If +argument+ is negative, it will be formatted as a two's complement
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prefixed with +..7+:
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sprintf('%o', 16) # => "20"
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# Prefix '..7' for negative value.
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sprintf('%o', -16) # => "..760"
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# Prefix zero for alternate format if positive.
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sprintf('%#o', 16) # => "020"
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sprintf('%#o', -16) # => "..760"
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==== Specifier +p+
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Format +argument+ as a string via <tt>argument.inspect</tt>:
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t = Time.now
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sprintf('%p', t) # => "2022-05-01 13:42:07.1645683 -0500"
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==== Specifier +s+
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Format +argument+ as a string via <tt>argument.to_s</tt>:
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t = Time.now
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sprintf('%s', t) # => "2022-05-01 13:42:07 -0500"
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Flag <tt>'#'</tt> does not apply.
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==== Specifiers +x+ and +X+
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Format +argument+ as a hexadecimal integer.
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If +argument+ is negative, it will be formatted as a two's complement
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prefixed with +..f+:
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sprintf('%x', 100) # => "64"
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# Prefix '..f' for negative value.
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sprintf('%x', -100) # => "..f9c"
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# Use alternate format.
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sprintf('%#x', 100) # => "0x64"
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# Alternate format for negative value.
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sprintf('%#x', -100) # => "0x..f9c"
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==== Specifier <tt>%</tt>
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Format +argument+ (<tt>'%'</tt>) as a single percent character:
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sprintf('%d %%', 100) # => "100 %"
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Flags do not apply.
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