# phpman > perldoc > Data::ShowTable

## NAME
    ShowTable - routines to display tabular data in several formats.

## USAGE
    "use [Data::ShowTable](https://www.chedong.com/phpMan.php/perldoc/Data%3A%3AShowTable/markdown);"

    ShowTable { *parameter* => *value*, ... };

    ShowTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub* ];

    ShowDatabases *\@dbnames*;

    ShowDatabases { *parameter* => *value*, ... };

    ShowTables *\@tblnames*;

    ShowTables { *parameter* => *value*, ... };

    ShowColumns *\@columns*, *\@col_types*, *\@col_lengths*, *\@col_attrs*;

    ShowColumns { *parameter* => *value*, ... };

    ShowBoxTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub* ];

    ShowBoxTable { *parameter* => *value*, ... };

    ShowSimpleTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub*];

    ShowSimpleTable { *parameter* => *value*, ... };

    ShowHTMLTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub*];

    ShowHTMLTable { *parameter* => *value*, ... };

    ShowListTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub*];

    ShowListTable { *parameter* => *value*, ... };

    "package [Data::ShowTable](https://www.chedong.com/phpMan.php/perldoc/Data%3A%3AShowTable/markdown)";

    $Show_Mode = '*mode*';

    $Max_Table_Width = *number*;

    $Max_List_Width = *number*;

    $No_Escape = *flag*;

    %URL_Keys = { "*$colname*" => "*$col_URL*", ... };

    @Title_Formats = ( *fmt1_html*, <fmt2_html>, ... );

    @Data_Formats = ( *fmt1_html*, <fmt2_html>, ... );

    ShowRow *$rewindflag*, *\$index*, *$col_array_1* [, *$col_array_2*, ...;]

    *$fmt* = ShowTableValue *$value*, *$type*, *$max_width*, *$width*, *$precision*, *$showmode*;

    [*$plaintext* = ] PlainText [*$htmltext*];

## DESCRIPTION
    The ShowTable module provides subroutines to display tabular data, typially from a database, in
    nicely formatted columns, in several formats. Its arguments can either be given in a fixed
    order, or, as a single, anonymous hash-array.

    The output format for any one invocation can be one of four possible styles:

    Box       A tabular format, with the column titles and the entire table surrounded by a "box" of
              ""+"", ""-"", and ""|"" characters. See "ShowBoxTable" for details.

    Table     A simple tabular format, with columns automatically aligned, with column titles. See
              "ShowSimpleTable".

    List      A *list* style, where columns of data are listed as a *name*:*value* pair, one pair
              per line, with rows being one or more column values, separated by an empty line. See
              "ShowListTable".

    HTML      The data is output as an HTML *TABLE*, suitable for display through a *Web*-client.
              See "ShowHTMLTable". Input can either be plain ASCII text, or text with embedded HTML
              elements, depending upon an argument or global parameter.

    The subroutines which perform these displays are listed below.

## EXPORTED NAMES
    This module exports the following subroutines:

     ShowDatabases    - show list of databases
     ShowTables       - show list of tables
     ShowColumns      - show table of column info
     ShowTable        - show a table of data
     ShowRow          - show a row from one or more columns
     ShowTableValue   - show a single column's value
     ShowBoxTable     - show a table of data in a box
     ShowListTable    - show a table of data in a list
     ShowSimpleTable  - show a table of data in a simple table
     ShowHTMLTable    - show a table of data using HTML
     PlainText        - convert HTML text into plain text

    All of these subroutines, and others, are described in detail in the following sections.

## MODULES
## ShowTable
    Format and display the contents of one or more rows of data.

      ShowTable { *parameter* => *value*, ... };

      ShowTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub* [, *$max_width* ] [,
    *$show_mode* ] ];

    The ShowTable subroutine displays tabular data aligned in columns, with headers. ShowTable
    supports four *modes* of display: Box, Table, List, and HTML. Each mode is described separately
    below.

    The arguments to ShowTable may be given in one of two ways: as a hashed-array, or by a
    combination of fixed order arguments, and some package-global variable settings. The hash-array
    parameters correspond to the fixed arguments and the global-parameter settings.

    In the list below, both the hash-array parameter name and the fixed-order argument name is given
    as the value. In the case where there is no fixed-order argument for a given parameter-value
    pair, then the corresponding global variable name is given.

    "titles" => *\@titles*
              A reference to an array of column names, or titles. If a particular column name is
              null, then the string "Field_*num*" is used by default. To have a column have no
              title, use the empty string.

    "types" => *\@types*
              A reference to an array of types, one for each column. These types are passed to the
              *fmt_sub* for appropriate formatting. Also, if a column type matches the regexp
              ""/text|char|string/i"", then the column alignment will be left-justified, otherwise
              it will be right-justified.

    "widths" => *\@widths*
              A reference to an array of column widths, which may be given as an integer, or as a
              string of the form: "*width*.*precision*".

    "row_sub" => *\&row_sub*
              A reference to a subroutine which successively returns rows of values in an array. It
              is called for two purposes, each described separately:

              * To fetch successive rows of data:

                  @row = &$[row_sub(0)](https://www.chedong.com/phpMan.php/man/rowsub/0/markdown);

              When given a null, zero, or empty argument, the next row is returned.

              * To initialize or rewind the data traversal.

                  $rewindable = &$[row_sub(1)](https://www.chedong.com/phpMan.php/man/rowsub/1/markdown);

              When invoked with a non-null argument, the subroutine should rewind its row pointer to
              start at the first row of data. If the data which *row_sub* is traversing is not
              rewindable, it must return zero or null. If the data is rewindable, a non-null,
              non-zero value should be returned.

              The *row_sub* must expect to be invoked once with a non-null argument, in order to
              discover whether or not the data is rewindable. If the data cannot be rewound,
              *row_sub* will thereafter only be called with a zero argument.

              Specifically, *row_sub* subroutine is used in this manner:

                  $rewindable = &$[row_sub(1)](https://www.chedong.com/phpMan.php/man/rowsub/1/markdown);
                  if ($rewindable) {
                      while ((@row = &$[row_sub(0)](https://www.chedong.com/phpMan.php/man/rowsub/0/markdown)), $#row >= 0) {
                          # examine lengths for optimal formatting
                      }
                      &$[row_sub(1)](https://www.chedong.com/phpMan.php/man/rowsub/1/markdown);   # rewind
                  }
                  while ((@row = &$[row_sub(0)](https://www.chedong.com/phpMan.php/man/rowsub/0/markdown)), $#row >= 0) {
                      # format the data
                  }

              The consequence of data that is not rewindable, a reasonably nice table will still be
              formatted, but it may contain fairly large amounts of whitespace for wide columns.

    "fmtsub" => *\&fmt_sub*
              A reference to a subroutine which formats a value, according to its type, width,
              precision, and the current column width. It is invoked either with a fixed list of
              arguments, or with a hash-array of parameter and value pairs.

                $string = &fmt_sub { I<parameter> => I<value>, ... };

                $string = &fmt_sub($value, $type, $max_width, $width, $precision)

              If *\&fmt_sub* is omitted, then a default subroutine, ShowTableValue, will be used,
              which will use Perl's standard string formatting rules.

              The arguments to *\&fmt_sub*, either as values passed in a fixed order, or as part of
              the parameter value pair, are described in the section on "ShowTableValue below.

    "max_width" => *number*,
              The maximum table width, including the table formatting characters. If not given,
              defaults to the global variable $Max_Table_Width;

    "show_mode" => '*mode*',
              The display mode of the output. One of five strings: 'Box', 'Table', 'Simple', 'List',
              and 'HTML'.

## ShowDatabases
    Show a list of database names.

      ShowDatabases *\@dbnames*;

      ShowDatabases { 'data' => *\@dbnames*, *parameter* => *value*, ...};

    ShowDatabases is intended to be used to display a list of database names, under the column
    heading of "Databases". It is a special case usage of ShowTable (and can thus be passed any
    parameter suitable for ShowTable.

    The argument, *\@dbnames*, is a reference to an array of strings, used as the values of the
    single column display.

## ShowTables
    Show an array of table names.

      ShowTables *\@tblnames*;

      ShowTables { 'data' => *\@tblnames*, *parameter* => *value*, ...};

    ShowTables is used to display a list of table names, under the column heading of "Tables". It is
    a special case usage of ShowTable, and can be passed any "ShowTable" argument parameter.

## ShowColumns
    Display a table of column names, types, and attributes.

      ShowColumns { *parameter* => *values*, ... };

      ShowColumns *\@columns*, *\@col_types*, *\@col_lengths*, *\@col_attrs*;

    The ShowColumns subroutine displays a table of column names, types, lengths, and other
    attributes in a nicely formatted table. It is a special case usage of ShowTable, and can be
    passed any argument suitable for "ShowTable";

    The arguments are:

    "columns" = *\@columns*
              An array of column names. This provides the value for the first column of the output.

    "col_types" = *\@col_types*
              An array of column types names. This provides the value for the second column.

    "col_lengths" = *\@col_lengths*
              An array of maximum lengths for corresponding columns. This provides the value for the
              third column of the output.

    "col_attrs" = *\@col_attrs*
              An array of column attributes array references (ie: an array of arrays). The
              attributes array for the first column are at "*$col_attrs*-\>[0]". The first attribute
              of the second column is "*$col_attrs*-\>[1][0]".

    The columns, types, lengths, and attributes are displayed in a table with the column headings:
    "Column", "Type", "Length", and "Attributes". This is a special case usage of ShowTable, and can
    be passed additional arguments suitable for "ShowTable".

## ShowBoxTable
    Show tabular data in a box.

      ShowBoxTable { *parameter* = *value*, ... };

      ShowBoxTable *\@titles*, *\@types*, *\@widths*, *\&row_sub*       [, [ *\&fmt_sub* ] [,
    *$max_width* ] ];

    The ShowBoxTable displays tabular data in titled columns using a "box" of ASCII graphics,
    looking something like this:

            +------------+----------+-----+----------+
            | Column1    | Column2  | ... | ColumnN  |
            +------------+----------+-----+----------+
            | Value11    | Value12  | ... | Value 1M |
            | Value21    | Value22  | ... | Value 2M |
            | Value31    | Value32  | ... | Value 3M |
            |  ...       |  ...     | ... |  ...     |
            | ValueN1    | ValueN2  | ... | Value NM |
            +------------+----------+-----+----------+

    The arguments are the same as with "ShowTable". If the *@titles* array is empty, the header row
    is omitted.

## ShowSimpleTable
    Display a table of data using a simple table format.

      ShowSimpleTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub*];

      ShowSimpleTable { *parameter* => *values*, ... };

    The ShowSimpleTable subroutine formats data into a simple table of aligned columns, in the
    following example:

       Column1  Column2  Column3
       -------  -------  -------
       Value1   Value2   Value3
       Value12  Value22  Value32

    Columns are auto-sized by the data's widths, plus two spaces between columns. Values which are
    too long for the maximum colulmn width are wrapped within the column.

## ShowHTMLTable
    Display a table of data nicely using HTML tables.

      ShowHTMLTable { *parameter* => *value*, ... };

      ShowHTMLTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub* [, *$max_width* [,
    *\%URL_Keys* [, *$no_escape* [, *\@title_formats* [, *\@data_formats* [, *$table_attrs* ] ] ] ]
    ] ] ];

    The ShowHTMLTable displays one or more rows of columns of data using the HTML "\<TABLE\">
    feature. In addition to the usual parameter arguments of "ShowTable", the following parameter
    arguments are defined:

    "url_keys" => *\%URL_Keys*,
              This is a hash array of column names (titles) and corresponding base URLs. The values
              of any column names or indexes occuring as keys in the hash array will be generated as
              hypertext anchors using the associated *printf*-like string as the base URL. Either
              the column name or the column index (beginning with 1) may be used as the hash key.

              In the string value, these macros can be substituted:

              "%K" is replaced with the column name.

              "%V" is replaced with the column value;

              "%I" is replaced with the column index.

              For example, if we define the array:

                  $base_url = "<http://www>.$domain/cgi/lookup?col=%K?val=%V";
                  %url_cols = ('Author' => $base_url,
                               'Name'   => $base_url);

              Then, the values in the "Author" column will be generated with the following HTML
              text:

                  <A HREF="<http://www>.$domain/cgi/lookup?col=Author?val=somevalue>somevalue</A>

              and the values in the "Name" column will be generated with the URL:

                  <A HREF="<http://www>.$domain/cgi/lookup?col=Name?val=othervalue>othervalue</A>

              If this variable is not given, it will default to the global variable "\%URL_Keys".

    "no_escape" => *boolean*,
              Unless $no_escape is set, HTML-escaping is performed on the data values in order to
              properly display the special HTML formatting characters : '\<', '\>', and '&'. If you
              wish to display data with embedded HTML text, you must set $no_escape.

              Enabling embedded HTML, turns on certain heuristics which enable the user to more
              completely define appearance of the table. For instance, any "\<TR\"> tokens found
              embedded *anywhere* within a row of data will be placed at the front of the row,
              within the generated "\<TR\">.

              Similarly, a row of data containing the "\<THEAD\"> or "\<TFOOT\"> tokens, and their
              closing counterparts, will begin and end, respectively a table header or footer data.

    "title_formats" => *\@title_formats*,
    "tformats" => *\@title_formats*,
              An array of HTML formatting elements for the column titles, one for each column. Each
              array element is a list of one or more HTML elements, given as "\<ELEMENT\"> or
              plainly, "ELEMENT", and separated by a comma ',', semi-colon ';', or vertical bar '|'.
              Each given HTML element is prepended to the corresponding column title, in the order
              given. The corresponding HTML closing elements are appended in the opposite order.

              For example, if *\@title_formats* contains the two elements:

                  [ 'FONT SIZE=+2,BOLD', 'FONT COLOR=red,EM' ]

              then the text output for the title of the first column would be:

                  <FONT SIZE=+2><BOLD>I<column_1_title></BOLD></FONT>

              If "title_formats" is omitted, the global variable @Title_Formats is used by default.

    "data_formats" => *\@data_formats*,
    "dformats" => *\@data_formats*,
              Similar to "title_formats", this array provides HTML formatting for the columns of
              each row of data. If "data_formats" is omitted or null, then the global variable
              \@Data_Formats is used by default.

    "table_attrs" => *$table_attrs*,
              This variable defines a string of attributes to be inserted within the "\<TABLE\">
              token. For example, if the user wishes to have no table border:

                  ShowHTMLTable {
                      ...
                      table_attrs => 'BORDER=0',
                      ...
                  };

## ShowListTable
    Display a table of data using a list format.

      ShowListTable { *parameter* => *value*, ... };

      ShowListTable *\@titles*, *\@types*, *\@widths*, *\&row_sub* [, *\&fmt_sub* [, *$max_width* [,
    *$wrap_margin* ] ] ];

    The arguments for ShowListTable are the same as for "ShowTable", except for those described
    next.

    "max_width" = *number*,
    "wrap_margin" = *number*,
              Lines are truncated, and wrapped when their length exceeds *$max_width*. Wrapping is
              done on a word-basis, unless the resulting right margin exceeds *$wrap_margin*, in
              which case the line is simply truncated at the *$max_width* limit.

              The *$max_width* variable defaults to $Max_List_Width. The *$wrap_margin* defaults to
              $List_Wrap_Margin.

    In *List* mode, columns (called "fields" in List mode) are displayed wth a field name and value
    pair per line, with records being one or more fields . In other words, the output of a table
    would look something like this:

        Field1_1: Value1_1
        Field1_2: Value1_2
        Field1_3: Value1_3
        ...
        Field1-N: Value1_M
        <empty line>
        Field2_1: Value2_1
        Field2_2: Value2_2
        Field2_3: Value2_3
        ...
        Field2_N: Value2_N
        ...
        FieldM_1: ValueM_1
        FieldM_2: ValueM_2
        ...
        FieldM_N: ValueM_N
        <empty line>
        <empty line>

    Characteristics of *List* mode:

    *         two empty lines indicate the end of data.

    *         An empty field (column) may be omitted, or may have a label, but no data.

    *         A long line can be continue by a null field (column):

                  Field2: blah blah blah
                        : blah blah blah

    *         On a continuation, the null field is an arbitrary number of leading white space, a
              colon ':', a single blank or tab, followed by the continued text.

    *         Embedded newlines are indicated by the escape mechanism "\n". Similarly, embedded tabs
              are indicated with "\t", returns with "\r".

    *         If the *@titles* array is empty, the field names ""Field_"*NN*" are used instead.

## ShowRow
    Fetch rows successively from one or more columns of data.

      ShowRow *$rewindflag*, *\$index*, *$col_array_1* [, *$col_array_2*, ...;]

    The ShowRow subroutine returns a row of data from one or more columns of data. It is designed to
    be used as a *callback* routine, within the ShowTable routine. It can be used to select elements
    from one or more array reference arguments.

    If passed two or more array references as arguments, elements of the arrays selected by *$index*
    are returned as the "row" of data.

    If a single array argument is passed, and each element of the array is itself an array, the
    subarray is returned as the "row" of data.

    If the *$rewindflag* flag is set, then the *$index* pointer is reset to zero, and "true" is
    returned (a scalar 1). This indicates that the data is rewindable to the ShowTable routines.

    When the *$rewindflag* is not set, then the current row of data, as determined by *$index* is
    returned, and *$index* will have been incremented.

    An actual invocation (from ShowColumns) is:

      ShowTable \@titles, \@types, \@lengths,
          sub { &ShowRow( $_[0], \$current_row, $col_names, $col_types,
                          $col_lengths, \@col_attrs); };

    In the example above, after each invocation, the *$current_row* argument will have been
    incremented.

## ShowTableValue
    Prepare and return a formatted representation of a value. A value argument, using its
    corresponding type, effective width, and precision is formatted into a field of a given maximum
    width.

      *$fmt* = ShowTableValue *$value*, *$type*, *$max_width*, *$width*, *$precision*, *$showmode*;

    "width" => *$width*
    *$width*  The width of the current value. If omittied, *$max_width* is assumed.

    "precision" => *$precision*
    *$precision*
              The number of decimal digits; zero is assumed if omittied.

    "value" => *$value*
    *$value*  The value to be formatted.

    *$type*   The type name of the value; eg: "char", "varchar", "int", etc.

    "maxwidth" => *$max_width*
    *$max_width*
              The maximum width of any value in the current value's column. If *$width* is zero or
              null, *$max_width* is used by default. *$max_width* is also used as a *minimum* width,
              in case *$width* is a smaller value.

    *$width*  The default width of the value, obtained from the width specification of the column in
              which this value occurs.

    *$precision*
              The precision specification, if any, from the column width specification.

    *$showmode*
              The mode of the output: one of "table", "list", "box", or "html". Currently, only the
              "html" mode is significant: it is used to avoid using HTML tokens as part of the
              formatted text and length calculations.

## PlainText
      *$plaintext* = &PlainText(*$htmltext*);

      &PlainText

    This function removes any HTML formatting sequences from the input argument, or from $_ if no
    argument is given. The resulting plain text is returned as the result.

## VARIABLES
    The following variables may be set by the user to affect the display (with the defaults enclosed
    in square brackets [..]):

    $Show_Mode [Box]
              This is the default display mode when using ShowTable. The environment variable,
              $ENV{'SHOW_MODE'}, is used when this variable is null or the empty string. The
              possible values for this variable are: "Box", "List", "Table", and "HTML". Case is
              insignificant.

    $List_Wrap_Margin [2]
              This variable's value determines how large a margin to keep before wrarpping a long
              value's display in a column. This value is only used in "List" mode.

    $Max_List_Width [80]
              This variable, used in "List" mode, is used to determine how long an output line may
              be before wrapping it. The environment variable, $ENV{'COLUMNS'}, is used to define
              this value when it is null.

    $Max_Table_Width ['']
              This variable, when set, causes all tables to have their columns scaled such that
              their total combined width does not exceed this value. When this variable is not set,
              which is the default case, there is no maximum table width, and no scaling will be
              done.

    $No_Escape ['']
              If set, allows embedded HTML text to be included in the data displayed in an
              HTML-formatted table. By default, the HTML formatting characters ("<", ">", and "&")
              occuring in values are escaped.

    %URL_Keys In HTML mode, this variable is used to recognize which columns are to be displayed
              with a corresponding hypertext anchor. See "ShowHTMLTable" for more details.

    @HTML_Elements
              An array of HTML elements (as of HTML 3.0) used to recognize and strip for width
              calculations.

    $HTML_Elements
              A regular expression string formed from the elements of @HTML_Elements.

## INTERNAL SUBROUTINES
get_params
      my *$args* = &get_params *\@argv*, *\%params*, *\@arglist*;

    Given the *@argv* originally passed to the calling sub, and the hash of named parameters as
    *%params*, and the array of parameter names in the order expected for a pass-by-value
    invocation, set the values of each of the variables named in *@vars*.

    If the only element of the *@argv* is a hash array, then set the variables to the values of
    their corresponding parameters used as keys to the hash array. If the parameter is not a key of
    the *%params* hash, and is not a key in the global hash %ShowTableParams, then an error is
    noted.

    When *@argv* has multiple elements, or is not a hash array, set each variable, in the order
    given within *@arglist*, to the values from the *@argv*, setting the variables named by each
    value in *%params*.

    Variables may given either by name or by reference.

    The result is a HASH array reference, either corresponding directly to the HASH array passed as
    the single argument, or one created by associating the resulting variable values to the
    parameter names associated with the variable names.

html_formats
      (*$prefixes*,*$suffixes*) = html_formats *\@html_formats*;

    The html_format function takes an array reference of HTML formatting elements *\@html_formats*,
    and builds two arrays of strings: the first: *$prefixes*, is an array of prefixes containing the
    corresponding HTML formatting elements from *\@html_formats*, and the second, *$suffixes*,
    containing the appropriate HTML closing elements, in the opposite order.

    The result is designed to be used as prefixes and suffixes for the corresponding titles and
    column values.

    The array *\@html_formats* contains lists of HTML formatting elements, one for each column
    (either title or data). Each array element is a list of one or more HTML elements, either given
    in HTML syntax, or as a "plain" name (ie: given as "\<ELEMENT\"> or plainly, "ELEMENT").
    Multiple elements are separated by a comma ','.

    The resulting array of *$prefixes* contains the corresponding opening elements, in the order
    given, with the proper HTML element syntax. The resulting array of *$suffixes* contains the
    closing elements, in the opposite order given, with the proper HTML element syntax.

    For example, if *\@html_formats* contains the two elements:

        [ 'FONT SIZE=+2,BOLD', 'FONT COLOR=red,EM' ]

    then the resulting two arrays will be returned as:

        [ [ '<FONT SIZE=+2><BOLD>', '<FONT COLOR=red><EM>' ],
          [ '</FONT></BOLD>',       '</FONT></EM>' ] ]

calc_widths
      (*$num_cols*, *$widths*, *$precision*, *$max_widths*) =   &calc_widths( *$widthspec*,
    *$titles*, *$rewindable*,       *$row_sub*, *$fmt_sub*, *$types*, *$showmode*,
          *$max_width*);

  DESCRIPTION
    calc_widths is a generalized subroutine used by all the ShowTable variant subroutines to setup
    internal variables prior to formatting for display. Calc_widths handles the column width and
    precision analysis, including scanning the data (if rewindable) for appropriate default values.

    The number of columns in the data is returned, as well as three arrays: the declared column
    widths, the column precision values, and the maximum column widths.

  RETURN VALUES
    *$num_cols*
              is the number of columns in the data. If the data is not rewindable, this is computed
              as the maximum of the number of elements in the *$widthspec* array and the number of
              elements in the *$titles* array. When the data is rewindable, this is the maximum of
              the number of columns of each row of data.

    *$widths* is the column widths array ref, without the precision specs (if any). Each column's
              width value is determined by the original *$widthspec* value and/or the maximum length
              of the formatted data for the column.

    *$precision*
              is the precision component (if any) of the original *$widthspec* array ref. If there
              was no original precision component from the *$widthspec*, and the data is rewindable,
              then the data is examined to determine the maximum default precision.

    *$max_widths*
              is the ref to the array of maximum widths for the given columns.

  ARGUMENTS
    *$widthspec*
              A reference to an array of column width (or length) values, each given as an integer,
              real number, or a string value of "*width*.*precision*". If a value is zero or null,
              the length of the corresponding formatted data (if rewindable) and column title length
              are used to determine a reasonable default.

              If a column's *width* portion is a positive, non-zero number, then the column will be
              this wide, regardless of the values lengths of the data in the column.

              If the column's *width* portion is given as a negative number, then the positive value
              is used as a minimum column width, with no limit on the maximum column width. In other
              words, the column will be at least *width* characters wide.

              If the data is not rewindable, and a column's width value is null or zero, then the
              length of the column title is used. This may cause severe wrapping of data in the
              column, if the column data lengths are much greater than the column title widths.

    *$titles* The array ref to the column titles; used to determine the minimum acceptable width, as
              well as the default number of columns. If the $titles array is empty, then the
              $widthspec array is used to determine the default number of columns.

    *$rewindable*
              A flag indicating whether or not the data being formatted is rewindable. If this is
              true, a pass over the data will be done in order to calculate the maximum lengths of
              the actual formatted data, using *$fmt_sub* (below), rather than just rely on the
              declared column lengths. This allows for optimal column width adjustments (ie: the
              actual column widths may be less than the declared column widths).

              If it is not desired to have the column widths dynamically adjusted, then set the
              *$rewindable* argument to 0, even if the data is rewindable.

    *$row_sub*
              The code reference to the subroutine which returns the data; invoked only if
              *$rewindable* is non-null.

    *$fmt_sub*
              The subroutine used to determine the length of the data when formatted; if this is
              omitted or null, the length of the data is used by default. The *$fmt_sub* is used
              only when the data is rewindable.

    *$types*  An array reference to the types of each of the value columns; used only when
              *$fmt_sub* is invoked.

    *$showmode*
              A string indicating the mode of the eventual display; one of four strings: ""box"",
              ""table"", ""list"", and ""html"". Used to adjust widths for formatting requirements.

    *$max_width*
              The maximum width of the table being formatted. If set, and the total sum of the
              individual columns exceeds this value, the column widths are scaled down uniformly. If
              not set (null), no column width scaling is done.

putcell
      *$wrapped* = &putcell( *\@cells*, *$c*, *$cell_width*, *\@prefix*, *\@suffix*, *$wrap_flag* );

    Output the contents of an array cell at *$cell*[*$c*], causing text longer than *$cell_width* to
    be saved for output on subsequent calls. Prefixing the output of each cell's value is a string
    from the two-element array *@prefix*. Suffixing each cell's value is a string from the
    two-element array *@suffix*. The first element of either array is selected when *$wrap_flag* is
    zero or null, or when there is no more text in the current to be output. The second element is
    selected when *$wrap_flag* is non-zero, and when there is more text in the current cell to be
    output.

    In the case of text longer than *$cell_width*, a non-zero value is returned.

    Cells with undefined data are not output, nor are the prefix or suffix strings.

center
    Center a string within a given width.

      *$field* = center *$string*, *$width*;

max
    Compute the maximum value from a list of values.

      *$max* = &max( *@values* );

min
    Compute the minum value from a list of values.

      *$min* = &min( *@values* );

max_length
    Compute the maximum length of a set of strings in an array reference.

      *$maxlength* = &max_length( *\@array_ref* );

htmltext
    Translate regular text for output into an HTML document. This means certain characters, such as
    "&", ">", and "<" must be escaped.

      *$output* = &htmltext( *$input* [, *$allflag* ] );

    If *$allflag* is non-zero, then all characters are escaped. Normally, only the four HTML
    syntactic break characters are escaped.

out
    Print text followed by a newline.

      out *$fmt* [, *@text* ];

put
    Print text (without a trailing newline).

      out *$fmt* [, *@text* ];

## AUTHOR
    Alan K. Stebbens <<aks@stebbens.org>>

## BUGS
    *         Embedded HTML is how the user can insert formatting overrides. However, the HTML
              formatting techniques have not been given much consideration -- feel free to provide
              constructive feedback.

