diff options
Diffstat (limited to 'doc/gawk.texi')
| -rw-r--r-- | doc/gawk.texi | 176 |
1 files changed, 139 insertions, 37 deletions
diff --git a/doc/gawk.texi b/doc/gawk.texi index e87a1e84..89921663 100644 --- a/doc/gawk.texi +++ b/doc/gawk.texi @@ -754,6 +754,8 @@ particular records in a file and perform operations upon them. * Arrays Summary:: Summary of arrays. * Built-in:: Summarizes the built-in functions. * Calling Built-in:: How to call built-in functions. +* Boolean Functions:: A function that returns Boolean + values. * Numeric Functions:: Functions that work with numbers, including @code{int()}, @code{sin()} and @code{rand()}. @@ -861,6 +863,7 @@ particular records in a file and perform operations upon them. * Programs Summary:: Summary of programs. * Programs Exercises:: Exercises. * Nondecimal Data:: Allowing nondecimal input data. +* Boolean Typed Values:: Values with @code{bool} type. * Array Sorting:: Facilities for controlling array traversal and sorting arrays. * Controlling Array Traversal:: How to use PROCINFO["sorted_in"]. @@ -18307,6 +18310,7 @@ but are summarized here for your convenience. @menu * Calling Built-in:: How to call built-in functions. +* Boolean Functions:: A function that returns Boolean values. * Numeric Functions:: Functions that work with numbers, including @code{int()}, @code{sin()} and @code{rand()}. * String Functions:: Functions for string manipulation, such as @@ -18376,6 +18380,25 @@ and 12. But if the order of evaluation is right to left, @code{i} first becomes 10, then 11, and @code{atan2()} is called with the two arguments 11 and 10. + +@node Boolean Functions +@subsection Generating Boolean Values +@cindex boolean function + +This function is specific to @command{gawk}. It is not +available in compatibility mode (@pxref{Options}): + +@c @asis for docbook +@table @asis +@item @code{bmkool(@var{expression})} +@cindexgawkfunc{mkbool} +Return a Boolean-typed value based on the regular Boolean value +of @var{expression}. Boolean ``true'' values have numeric value one. +Boolean ``false'' values have numeric +zero. This is discussed in more +detail in @ref{Boolean Typed Values}. +@end table + @node Numeric Functions @subsection Numeric Functions @cindex numeric @subentry functions @@ -20898,6 +20921,9 @@ Return one of the following strings, depending upon the type of @var{x}: @item "number" @var{x} is a number. +@item "number|bool" +@var{x} is a Boolean typed value (@pxref{Boolean Typed Values}). + @item "string" @var{x} is a string. @@ -21776,7 +21802,7 @@ being aware of them. @cindex pointers to functions @cindex differences in @command{awk} and @command{gawk} @subentry indirect function calls -This section describes an advanced, @command{gawk}-specific extension. +This @value{SECTION} describes an advanced, @command{gawk}-specific extension. Often, you may wish to defer the choice of function to call until runtime. For example, you may have different kinds of records, each of which @@ -29385,6 +29411,7 @@ discusses the ability to dynamically add new built-in functions to @menu * Nondecimal Data:: Allowing nondecimal input data. +* Boolean Typed Values:: Values with @code{number|bool} type. * Array Sorting:: Facilities for controlling array traversal and sorting arrays. * Two-way I/O:: Two-way communications with another process. @@ -29451,6 +29478,49 @@ leads to less surprising results. This option may disappear in a future version of @command{gawk}. @end quotation +@node Boolean Typed Values +@section Boolean Typed Values + +Scalar values in @command{awk} are either numbers or strings. +@command{gawk} also supports values of type @code{regexp} +(@pxref{Strong Regexp Constants}). + +As described in @ref{Truth Values}, Boolean values in @command{awk} +don't have a separate type: a value counts as ``true'' if it is nonzero +or non-null, and as ``false'' otherwise. + +When interchanging data with languages that do have a real Boolean type, +using a standard format such as JSON or XML, the lack of a true Boolean +type in @command{awk} is problematic. +(See, for example, the @code{json} extension provided by +@uref{https://sourceforge.net/projects/gawkextlib, the @code{gawkextlib} project}.) + +It's easy to import Boolean data into @command{awk}, but then the fact +that it was originally Boolean is lost. Exporting data is even harder; +there's no way to indicate that a value is really Boolean. + +To solve this problem, @command{gawk} provides a function named @code{mkbool()}. +It takes one argument, which is any @command{awk} expression, and it +returns a value of Boolean type. + +The returned values are normal @command{awk} numeric values, with +values of either one or zero, +depending upon the truth +value of the original expression passed in the call to @code{bool()}. + +The @code{typeof()} function (@pxref{Type Functions}) returns +@code{"number|bool"} for these values. + +Thus Boolean-typed values @emph{are} numbers as far as @command{gawk} +is concerned, except that extension code can treat them as Booleans +if desired. + +While it would have been possible to add two new built-in variables +of Boolean type named @code{TRUE} and @code{FALSE}, doing so would +undoubtedly have broken many existing @command{awk} programs. Instead, +having a ``generator'' function that creates Boolean values gives +flexibility, without breaking as much existing code. + @node Array Sorting @section Controlling Array Traversal and Array Sorting @@ -35586,7 +35656,8 @@ multibyte encoding. @itemx @ @ @ @ AWK_STRNUM, @itemx @ @ @ @ AWK_ARRAY, @itemx @ @ @ @ AWK_SCALAR,@ @ @ @ @ @ @ @ @ /* opaque access to a variable */ -@itemx @ @ @ @ AWK_VALUE_COOKIE@ @ @ @ /* for updating a previously created value */ +@itemx @ @ @ @ AWK_VALUE_COOKIE,@ @ @ /* for updating a previously created value */ +@itemx @ @ @ @ AWK_BOOL @itemx @} awk_valtype_t; This @code{enum} indicates the type of a value. It is used in the following @code{struct}. @@ -35599,6 +35670,7 @@ It is used in the following @code{struct}. @itemx @ @ @ @ @ @ @ @ awk_array_t@ @ @ @ @ @ @ @ a; @itemx @ @ @ @ @ @ @ @ awk_scalar_t@ @ @ @ @ @ @ scl; @itemx @ @ @ @ @ @ @ @ awk_value_cookie_t@ vc; +@itemx @ @ @ @ @ @ @ @ awk_bool_t@ @ @ @ @ @ @ @ @ b; @itemx @ @ @ @ @} u; @itemx @} awk_value_t; An ``@command{awk} value.'' @@ -35614,6 +35686,7 @@ The @code{val_type} member indicates what kind of value the @itemx #define array_cookie@ @ @ u.a @itemx #define scalar_cookie@ @ u.scl @itemx #define value_cookie@ @ @ u.vc +@itemx #define bool_value@ @ @ @ @ u.b Using these macros makes accessing the fields of the @code{awk_value_t} more readable. @@ -35941,6 +36014,11 @@ the regular expression of length @code{len}. It expects @code{string} to be a @samp{char *} value pointing to data previously obtained from @code{gawk_malloc()}, @code{gawk_calloc()}, or @code{gawk_realloc()}. +@item static inline awk_value_t * +@itemx make_bool(awk_bool_t boolval, awk_value_t *result); +This function creates a boolean value in the @code{awk_value_t} variable +pointed to by @code{result}. + @end table @node API Ownership of MPFR and GMP Values @@ -36741,7 +36819,8 @@ value type, as appropriate. This behavior is summarized in <colspec colname="c6"/> <colspec colname="c7"/> <colspec colname="c8"/> - <spanspec spanname="hspan" namest="c3" nameend="c8" align="center"/> + <colspec colname="c9"/> + <spanspec spanname="hspan" namest="c3" nameend="c9" align="center"/> <thead> <row><entry></entry><entry spanname="hspan"><para>Type of Actual Value</para></entry></row> <row> @@ -36751,6 +36830,7 @@ value type, as appropriate. This behavior is summarized in <entry><para>Strnum</para></entry> <entry><para>Number</para></entry> <entry><para>Regex</para></entry> + <entry><para>Bool</para></entry> <entry><para>Array</para></entry> <entry><para>Undefined</para></entry> </row> @@ -36763,6 +36843,7 @@ value type, as appropriate. This behavior is summarized in <entry><para>String</para></entry> <entry><para>String</para></entry> <entry><para>String</para></entry> + <entry><para>String</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> </row> @@ -36775,6 +36856,7 @@ value type, as appropriate. This behavior is summarized in <entry><para>false</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> + <entry><para>false</para></entry> </row> <row> <entry></entry> @@ -36783,6 +36865,7 @@ value type, as appropriate. This behavior is summarized in <entry><para>Number</para></entry> <entry><para>Number</para></entry> <entry><para>false</para></entry> + <entry><para>Number</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> </row> @@ -36791,6 +36874,7 @@ value type, as appropriate. This behavior is summarized in <entry><para><emphasis role="bold">Regex</emphasis></para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> + <entry><para>false</para></entry> <entry><para>Regex</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> @@ -36798,11 +36882,23 @@ value type, as appropriate. This behavior is summarized in </row> <row> <entry><para><emphasis role="bold">Requested</emphasis></para></entry> + <entry><para><emphasis role="bold">Bool</emphasis></para></entry> + <entry><para>false</para></entry> + <entry><para>false</para></entry> + <entry><para>false</para></entry> + <entry><para>false</para></entry> + <entry><para>Bool</para></entry> + <entry><para>false</para></entry> + <entry><para>false</para></entry> + </row> + <row> + <entry><para></para></entry> <entry><para><emphasis role="bold">Array</emphasis></para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> + <entry><para>false</para></entry> <entry><para>Array</para></entry> <entry><para>false</para></entry> </row> @@ -36813,6 +36909,7 @@ value type, as appropriate. This behavior is summarized in <entry><para>Scalar</para></entry> <entry><para>Scalar</para></entry> <entry><para>Scalar</para></entry> + <entry><para>Scalar</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> </row> @@ -36823,6 +36920,7 @@ value type, as appropriate. This behavior is summarized in <entry><para>Strnum</para></entry> <entry><para>Number</para></entry> <entry><para>Regex</para></entry> + <entry><para>Bool</para></entry> <entry><para>Array</para></entry> <entry><para>Undefined</para></entry> </row> @@ -36835,6 +36933,7 @@ value type, as appropriate. This behavior is summarized in <entry><para>false</para></entry> <entry><para>false</para></entry> <entry><para>false</para></entry> + <entry><para>false</para></entry> </row> </tbody> </tgroup> @@ -36851,43 +36950,46 @@ value type, as appropriate. This behavior is summarized in \vglue-1.1\baselineskip @end tex @c @multitable @columnfractions .166 .166 .198 .15 .15 .166 -@multitable {Requested} {Undefined} {Number} {Number} {Scalar} {Regex} {Array} {Undefined} -@headitem @tab @tab String @tab Strnum @tab Number @tab Regex @tab Array @tab Undefined -@item @tab @b{String} @tab String @tab String @tab String @tab String @tab false @tab false -@item @tab @b{Strnum} @tab false @tab Strnum @tab Strnum @tab false @tab false @tab false -@item @tab @b{Number} @tab Number @tab Number @tab Number @tab false @tab false @tab false -@item @b{Type} @tab @b{Regex} @tab false @tab false @tab false @tab Regex @tab false @tab false -@item @b{Requested} @tab @b{Array} @tab false @tab false @tab false @tab false @tab Array @tab false -@item @tab @b{Scalar} @tab Scalar @tab Scalar @tab Scalar @tab Scalar @tab false @tab false -@item @tab @b{Undefined} @tab String @tab Strnum @tab Number @tab Regex @tab Array @tab Undefined -@item @tab @b{Value cookie} @tab false @tab false @tab false @tab false @tab false @tab false +@multitable {Requested} {Undefined} {Number} {Number} {Scalar} {Regex} {Number} {Array} {Undefined} +@headitem @tab @tab String @tab Strnum @tab Number @tab Regex @tab Bool @tab Array @tab Undefined +@item @tab @b{String} @tab String @tab String @tab String @tab String @tab String @tab false @tab false +@item @tab @b{Strnum} @tab false @tab Strnum @tab Strnum @tab false @tab false @tab false @tab false +@item @tab @b{Number} @tab Number @tab Number @tab Number @tab false @tab Number @tab false @tab false +@item @b{Type} @tab @b{Regex} @tab false @tab false @tab false @tab Regex @tab false @tab false @tab false +@item @b{Requested} @tab @b{Bool} @tab false @tab false @tab false @tab false @tab Bool @tab false @tab false +@item @tab @b{Array} @tab false @tab false @tab false @tab false @tab false @tab Array @tab false +@item @tab @b{Scalar} @tab Scalar @tab Scalar @tab Scalar @tab Scalar @tab Scalar @tab false @tab false +@item @tab @b{Undefined} @tab String @tab Strnum @tab Number @tab Regex @tab Bool @tab Array @tab Undefined +@item @tab @b{Value cookie} @tab false @tab false @tab false @tab false @tab false @tab false @tab false @end multitable @end ifnotdocbook @end ifnotplaintext @ifplaintext @verbatim - +-------------------------------------------------------+ - | Type of Actual Value: | - +--------+--------+--------+--------+-------+-----------+ - | String | Strnum | Number | Regex | Array | Undefined | -+-----------+-----------+--------+--------+--------+--------+-------+-----------+ -| | String | String | String | String | String | false | false | -| +-----------+--------+--------+--------+--------+-------+-----------+ -| | Strnum | false | Strnum | Strnum | false | false | false | -| +-----------+--------+--------+--------+--------+-------+-----------+ -| | Number | Number | Number | Number | false | false | false | -| +-----------+--------+--------+--------+--------+-------+-----------+ -| | Regex | false | false | false | Regex | false | false | -| Type +-----------+--------+--------+--------+--------+-------+-----------+ -| Requested | Array | false | false | false | false | Array | false | -| +-----------+--------+--------+--------+--------+-------+-----------+ -| | Scalar | Scalar | Scalar | Scalar | Scalar | false | false | -| +-----------+--------+--------+--------+--------+-------+-----------+ -| | Undefined | String | Strnum | Number | Regex | Array | Undefined | -| +-----------+--------+--------+--------+--------+-------+-----------+ -| | Value | false | false | false | false | false | false | -| | Cookie | | | | | | | -+-----------+-----------+--------+--------+--------+--------+-------+-----------+ + +----------------------------------------------------------------+ + | Type of Actual Value: | + +--------+--------+--------+--------+--------+-------+-----------+ + | String | Strnum | Number | Regex | Bool | Array | Undefined | ++-----------+-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | String | String | String | String | String | String | false | false | +| +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | Strnum | false | Strnum | Strnum | false | false | false | false | +| +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | Number | Number | Number | Number | false | Number | false | false | +| +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | Regex | false | false | false | Regex | false | false | false | +| +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| Type | Bool | false | false | false | false | Bool | false | false | +| Requested +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | Array | false | false | false | false | false | Array | false | +| +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | Scalar | Scalar | Scalar | Scalar | Scalar | Scalar | false | false | +| +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | Undefined | String | Strnum | Number | Regex | Bool | Array | Undefined | +| +-----------+--------+--------+--------+--------+--------+-------+-----------+ +| | Value | false | false | false | false | false | false | false | +| | Cookie | | | | | | | | ++-----------+-----------+--------+--------+--------+--------+--------+-------+-----------+ @end verbatim @end ifplaintext @end float @@ -45202,8 +45304,8 @@ internationalized program to work in a particular language. @item Logical Expression An expression using the operators for logic, AND, OR, and NOT, written -@samp{&&}, @samp{||}, and @samp{!} in @command{awk}. Often called Boolean -expressions, after the mathematician who pioneered this kind of +@samp{&&}, @samp{||}, and @samp{!} in @command{awk}. Often called @dfn{Boolean +expressions}, after the mathematician who pioneered this kind of mathematical logic. @item Lvalue |