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Diffstat (limited to 'doc/gawk.texi')
| -rw-r--r-- | doc/gawk.texi | 59 |
1 files changed, 58 insertions, 1 deletions
diff --git a/doc/gawk.texi b/doc/gawk.texi index 88b0a2ca..280b3168 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 +18380,22 @@ 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 functions is specific to @command{gawk}. It is not +available in compatibility mode (@pxref{Options}): + +@c @asis for docbook +@table @asis +@item @code{bool(@var{expression})} +@cindexgawkfunc{bool} + +blah blah +@end table + @node Numeric Functions @subsection Numeric Functions @cindex numeric @subentry functions @@ -21776,7 +21796,7 @@ 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 +29405,7 @@ discusses the ability to dynamically add new built-in functions to @menu * Nondecimal Data:: Allowing nondecimal input data. +* Boolean Typed Values:: Values with @code{bool} type. * Array Sorting:: Facilities for controlling array traversal and sorting arrays. * Two-way I/O:: Two-way communications with another process. @@ -29451,6 +29472,42 @@ 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 + +This @value{SECTION} describes an advanced, @command{gawk}-specific extension. + +Scalar values in @command{awk} are either numbers or strings. +@command{gawk} also supports values of type @code{regexp} (FIXME pxref). + +As seen in FIXME @@ref@{@} here, 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. (FIXME: xref to gawkextlib json +extension) + +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{bool()}. +It takes one argument, which is any @command{awk} expression, and it +returns a value of Boolean type. + +The returned values are different than +normal @command{awk} values. When treated as numbers, they are either +one or zero, depending upon the truth value of the expression passed +in the call. When treated as strings, they are either @code{"TRUE"} +or @code{"FALSE"}, again depending upon the truth value of the expression passed +in the call. The value for ``false'' is thus unusual; it is zero numerically, +but not empty when treated as a string. + +The @code{typeof()} function (FIXME pxref here) returns @code{"bool"} +for these values. + @node Array Sorting @section Controlling Array Traversal and Array Sorting |