Minor improvements to format field numbers
* src/editfns.c (styled_format): Allow field numbers in a %% spec. No need for a special diagnostic for field numbers greater than PTRDIFF_MAX. Reword diagnostic for field 0. * test/src/editfns-tests.el (format-with-field): Adjust to match.
This commit is contained in:
Paul Eggert
Philipp Stephani
parent
0dd1bbb0bb
commit
5324710841
4 changed files with 89 additions and 118 deletions
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@ -864,15 +864,6 @@ below, as the first argument, and the string as the second, like this:
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(format "%s" @var{arbitrary-string})
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@end example
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If @var{string} contains more than one format specification and none
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of the format specifications contain an explicit field number, the
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format specifications correspond to successive values from
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@var{objects}. Thus, the first format specification in @var{string}
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uses the first such value, the second format specification uses the
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second such value, and so on. Any extra format specifications (those
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for which there are no corresponding values) cause an error. Any
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extra values to be formatted are ignored.
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Certain format specifications require values of particular types. If
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you supply a value that doesn't fit the requirements, an error is
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signaled.
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@ -962,33 +953,84 @@ operation} error.
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@end group
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@end example
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@cindex field numbers in format spec
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A specification can have a @dfn{field number}, which is a decimal
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number after the initial @samp{%}, followed by a literal dollar sign
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@samp{$}. If you provide a field number, then the argument to be
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printed corresponds to the given field number instead of the next
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argument. Field numbers start at 1.
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By default, format specifications correspond to successive values from
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@var{objects}. Thus, the first format specification in @var{string}
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uses the first such value, the second format specification uses the
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second such value, and so on. Any extra format specifications (those
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for which there are no corresponding values) cause an error. Any
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extra values to be formatted are ignored.
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You can mix specifications with and without field numbers. A
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@cindex field numbers in format spec
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A format specification can have a @dfn{field number}, which is a
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decimal number immediately after the initial @samp{%}, followed by a
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literal dollar sign @samp{$}. It causes the format specification to
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convert the argument with the given number instead of the next
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argument. Argument 1 is the argument just after the format.
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You can mix specifications with and without field numbers. A
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specification without a field number that follows a specification with
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a field number will convert the argument after the one specified by
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the field number:
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@example
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(format "First argument %2$s, then %s, then %1$s" 1 2 3)
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@result{} "First argument 2, then 3, then 1"
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(format "Argument %2$s, then %s, then %1$s" "x" "y" "z")
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@result{} "Argument y, then z, then x"
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@end example
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You can't use field numbers in a @samp{%%} specification.
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@cindex flags in format specifications
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After the @samp{%} and any field number, you can put certain
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@dfn{flag characters}.
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The flag @samp{+} inserts a plus sign before a positive number, so
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that it always has a sign. A space character as flag inserts a space
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before a positive number. (Otherwise, positive numbers start with the
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first digit.) These flags are useful for ensuring that positive
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numbers and negative numbers use the same number of columns. They are
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ignored except for @samp{%d}, @samp{%e}, @samp{%f}, @samp{%g}, and if
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both flags are used, @samp{+} takes precedence.
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The flag @samp{#} specifies an alternate form which depends on
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the format in use. For @samp{%o}, it ensures that the result begins
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with a @samp{0}. For @samp{%x} and @samp{%X}, it prefixes the result
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with @samp{0x} or @samp{0X}. For @samp{%e} and @samp{%f}, the
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@samp{#} flag means include a decimal point even if the precision is
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zero. For @samp{%g}, it always includes a decimal point, and also
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forces any trailing zeros after the decimal point to be left in place
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where they would otherwise be removed.
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The flag @samp{0} ensures that the padding consists of @samp{0}
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characters instead of spaces. This flag is ignored for non-numerical
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specification characters like @samp{%s}, @samp{%S} and @samp{%c}.
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These specification characters accept the @samp{0} flag, but still pad
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with @emph{spaces}.
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The flag @samp{-} causes any padding inserted by the width,
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if specified, to be inserted on the right rather than the left.
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If both @samp{-} and @samp{0} are present, the @samp{0} flag is
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ignored.
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@example
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@group
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(format "%06d is padded on the left with zeros" 123)
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@result{} "000123 is padded on the left with zeros"
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(format "'%-6d' is padded on the right" 123)
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@result{} "'123 ' is padded on the right"
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(format "The word '%-7s' actually has %d letters in it."
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"foo" (length "foo"))
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@result{} "The word 'foo ' actually has 3 letters in it."
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@end group
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@end example
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@cindex field width
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@cindex padding
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A specification can have a @dfn{width}, which is a decimal number
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between the @samp{%} and the specification character. If the printed
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that appears after any field number and flags. If the printed
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representation of the object contains fewer characters than this
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width, @code{format} extends it with padding. The width specifier is
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width, @code{format} extends it with padding. The width is
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ignored for the @samp{%%} specification. Any padding introduced by
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the width specifier normally consists of spaces inserted on the left:
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the width normally consists of spaces inserted on the left:
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@example
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(format "%5d is padded on the left with spaces" 123)
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@ -1016,60 +1058,9 @@ is not truncated.
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@end group
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@end example
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If you want to use both a field number and a width, place the field
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number before the width. For example, in @samp{%2$7s}, @samp{2} is
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the field number and @samp{7} is the width.
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@cindex flags in format specifications
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After the @samp{%} and before the optional width specifier, you can
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also put certain @dfn{flag characters}. The flag characters need to
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come directly after a potential field number.
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The flag @samp{+} inserts a plus sign before a positive number, so
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that it always has a sign. A space character as flag inserts a space
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before a positive number. (Otherwise, positive numbers start with the
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first digit.) These flags are useful for ensuring that positive
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numbers and negative numbers use the same number of columns. They are
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ignored except for @samp{%d}, @samp{%e}, @samp{%f}, @samp{%g}, and if
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both flags are used, @samp{+} takes precedence.
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The flag @samp{#} specifies an alternate form which depends on
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the format in use. For @samp{%o}, it ensures that the result begins
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with a @samp{0}. For @samp{%x} and @samp{%X}, it prefixes the result
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with @samp{0x} or @samp{0X}. For @samp{%e} and @samp{%f}, the
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@samp{#} flag means include a decimal point even if the precision is
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zero. For @samp{%g}, it always includes a decimal point, and also
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forces any trailing zeros after the decimal point to be left in place
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where they would otherwise be removed.
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The flag @samp{0} ensures that the padding consists of @samp{0}
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characters instead of spaces. This flag is ignored for non-numerical
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specification characters like @samp{%s}, @samp{%S} and @samp{%c}.
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These specification characters accept the @samp{0} flag, but still pad
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with @emph{spaces}.
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The flag @samp{-} causes the padding inserted by the width
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specifier, if any, to be inserted on the right rather than the left.
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If both @samp{-} and @samp{0} are present, the @samp{0} flag is
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ignored.
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@example
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@group
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(format "%06d is padded on the left with zeros" 123)
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@result{} "000123 is padded on the left with zeros"
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(format "'%-6d' is padded on the right" 123)
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@result{} "'123 ' is padded on the right"
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(format "The word '%-7s' actually has %d letters in it."
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"foo" (length "foo"))
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@result{} "The word 'foo ' actually has 3 letters in it."
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@end group
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@end example
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@cindex precision in format specifications
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All the specification characters allow an optional @dfn{precision}
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before the character (after the width, if present). The precision is
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after the field number, flags and width, if present. The precision is
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a decimal-point @samp{.} followed by a digit-string. For the
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floating-point specifications (@samp{%e} and @samp{%f}), the
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precision specifies how many digits following the decimal point to
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2
etc/NEWS
2
etc/NEWS
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@ -369,7 +369,7 @@ libraries: 'find-library-other-window' and 'find-library-other-frame'.
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display of raw bytes from octal to hex.
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** You can now provide explicit field numbers in format specifiers.
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For example, '(format "%2$s %1$s" 1 2)' produces "2 1".
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For example, '(format "%2$s %1$s" "X" "Y")' produces "Y X".
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* Editing Changes in Emacs 26.1
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@ -4046,9 +4046,8 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
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field-width ::= [0-9]+
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precision ::= '.' [0-9]*
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If a field-number is specified, it specifies the argument
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number to substitute. Otherwise, the next argument is
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taken.
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If present, a field-number specifies the argument number
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to substitute. Otherwise, the next argument is taken.
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If a field-width is specified, it specifies to which width
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the output should be padded with blanks, if the output
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@ -4058,28 +4057,20 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
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digits to print after the '.' for floats, or the max.
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number of chars to print from a string. */
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char *field_end;
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uintmax_t raw_field = strtoumax (format, &field_end, 10);
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bool has_field = false;
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if (c_isdigit (*format) && *field_end == '$')
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{
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if (raw_field < 1 || raw_field >= PTRDIFF_MAX)
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{
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/* doprnt doesn't support %.*s, so we need to copy
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the field number string. */
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ptrdiff_t length = field_end - format;
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eassert (length > 0);
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eassert (length < PTRDIFF_MAX);
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char *field = SAFE_ALLOCA (length + 1);
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memcpy (field, format, length);
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field[length] = '\0';
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error ("Invalid field number `%s'", field);
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}
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has_field = true;
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/* n is incremented below. */
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n = raw_field - 1;
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format = field_end + 1;
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}
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uintmax_t num;
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char *num_end;
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if (c_isdigit (*format))
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{
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num = strtoumax (format, &num_end, 10);
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if (*num_end == '$')
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{
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if (num == 0)
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error ("Invalid format field number 0");
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n = min (num, PTRDIFF_MAX);
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n--;
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format = num_end + 1;
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}
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}
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bool minus_flag = false;
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bool plus_flag = false;
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@ -4104,11 +4095,10 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
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space_flag &= ! plus_flag;
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zero_flag &= ! minus_flag;
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char *num_end;
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uintmax_t raw_field_width = strtoumax (format, &num_end, 10);
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if (max_bufsize <= raw_field_width)
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num = strtoumax (format, &num_end, 10);
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if (max_bufsize <= num)
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string_overflow ();
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ptrdiff_t field_width = raw_field_width;
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ptrdiff_t field_width = num;
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bool precision_given = *num_end == '.';
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uintmax_t precision = (precision_given
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@ -4123,13 +4113,7 @@ styled_format (ptrdiff_t nargs, Lisp_Object *args, bool message)
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memset (&discarded[format0 - format_start], 1,
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format - format0 - (conversion == '%'));
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if (conversion == '%')
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{
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if (has_field)
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/* FIXME: `error' doesn't appear to support `%%'. */
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error ("Field number specified together with `%c' conversion",
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'%');
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goto copy_char;
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}
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goto copy_char;
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++n;
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if (! (n < nargs))
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@ -186,13 +186,9 @@
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(should (equal (should-error (format "a %999999$s b" 11))
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'(error "Not enough arguments for format string")))
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(should (equal (should-error (format "a %$s b" 11))
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;; FIXME: there shouldn't be two % in the error
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;; string!
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'(error "Invalid format operation %%$")))
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'(error "Invalid format operation %$")))
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(should (equal (should-error (format "a %0$s b" 11))
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'(error "Invalid field number `0'")))
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(should (equal
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(should-error (format "a %1$% %s b" 11))
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'(error "Field number specified together with `%' conversion"))))
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'(error "Invalid format field number 0")))
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(should (equal (format "a %1$% %s b" 11) "a % 11 b")))
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;;; editfns-tests.el ends here
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