Scroll to navigation

FBB::CSVTable(3bobcat) Table Construction FBB::CSVTable(3bobcat)

NAME

FBB::CSVTable - sequentially fills tables row-wise

SYNOPSIS

#include <bobcat/csvtable>
Linking option: -lbobcat

DESCRIPTION

FBB::CSVTable is used to fill tables row-wise. By default the table’s elements are comma-separated. The elements may contain any type of data that can also be inserted into std::ostreams, as may also contain horizontal lines (optionally spanning multiple columns).

Before inserting elements into the table the widths, alignment types and precisions of the table’s columns are defined. By default values are right-aligned. While inserting table elements the alignment types and precisions may be altered for specific elements, optionally spanning multiple columns. When inserting values whose representations require more characters than the current widths of the columns receiving those values then those larger widths take precedence over the defined column widths.

Different from tables defined by FBB::Table(3bobcat) all data inserted into CSVTables do not have to be completely available before the table is inserted into a destination std::ostream. As the table’s column formats are known before entering the data the CSVTable knows which format to use for which column. These column format specifications may be defined in multiple ways, e.g., by using text labels and values. CSVTable objects always use the widest column specifications and alignment types that were specified last.

When inserting elements into CSVTables the standard C++ IO manipulators can also be used. Table rows do not automatically end after the table’s last column has been filled. But when inserting elements beyond the last column they are inserted as-is (but then the standard I/O format specifications can optionally be used).

Table column definitions and table rows end at the end of insertion statements (see below at the descriptions of the various operator<< functions).

CSVTable uses two support classes handling, respectively, the definitions of the characteristics of the table’s columns and inserting values into the table’s elements. CSVTabDef handles the table’s column definitions, CSVTabIns handles insertions into the table elements. Their main characteristics are various insertion operators which are described below.

Constructing tables normally consists of two steps: first the characteristics of the columns are defined, then values are inserted into the table’s elements. This sequence is not enforced by CSVTable: after inserting values into the table column definitions may be updated, whereafter additional values may be inserted into the table which then use the updated column definitions.

NAMESPACE

FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB.

INHERITS FROM

-

FMT

FMT objects are returned by several free functions (like left, described below in section FREE FUNCTIONS), and FMT defines the enumeration Align (see the next section) specifying alignment types. FMT objects are internally used by CSVTable objects. A FMT object specifies the width, the precision when floating point numbers are inserted, the column’s alignment type (left, right or centered), and the number of table columns to use.

FMT objects can be inserted into std::ostream objects showing its characteristics. In addition it offers the following (const) accessors:

FMT::Align align():
the alignment value;
unsigned nCols():
the number of occupied columns;
unsigned precision():
the precision used when inserting a floating point value (~0U (= -1 as int) is returned if precision is not used). The insertion operator shows precision: -1 when precision is ~0U;
unsigned width():
the width in number of characters;

The static member char const *FMT::align(FMT::Align value) returns the textual label corresponding to value.

ALIGN ENUM

The enum FMT::Align defines the following values indicating the alignment types of the columns of the table:

FMT::Align::CENTER:
The information inserted in the column is centered;
FMT::Align::LEFT:
The information inserted in the column is left-aligned;
FMT::Align::RIGHT:
The information inserted in the column is right-aligned (this is the alignment used by default);

In addition, when inserting horizontal lines, the value FMT::Align::HLINE is used.

CONSTRUCTORS

CSVTable(std::ostream &out = std::cout, std::string const &sep = ", "):
This constructor by default writes its table to std::cout and uses a comma followed by a space character as column separator. During the table’s construction the stream to write the table to can be altered using the stream members, and the separator can be changed using the sep member, but the separator can also be changed while filling the table’s elements (see below). When the CSVTable object goes out of scope the stream’s original configuration is restored;
CSVTable(std::ofstream &&tmp, std::string const &sep = ", "):
This constructor by default uses the same separator to separate the column’s elements as the first constructor, but writes the table to the ofstream tmp, which is grabbed by CSVTable;
CSVTable(std::string const &fname, std::string const &sep = ", "), std::ios::openmode mode = ios::out:
This constructor by default uses the same separator to separate the column’s elements as the first constructor, but writes the table to the file having (path)name fname, by default (re)writing the file. If the file already exists and CSVTable should start writing at the file’s end use, e.g., ios::ate | ios::in. An exception is thrown if the specified file cannot be opened.

The move constructor and assignment operator are available; the copy constructor and assignment operator are not available.

OVERLOADED OPERATORS

In the provided examples tab refers to an existing CSVTable object. Each insertion statement (note: not insertion expression) either defines or updates the table columns’ definitions or fills the next row of the table with data.

Defining column characteristics

The return types and left-hand side operands of the following insertion operators are specified as CSVTabDef. The member fmt() (cf. section MEMBER FUNCTIONS) returns a CSVTabDef object which is then used in combination with the following insertion operators to define the characteristics of the table’s columns.

CSVTabDef &operator<<(CSVTabDef &tab, FMT const &fmt):
This insertion operator defines the characteristics of the next table column. FMT objects inserted into CSVTabDef objects must have been returned by center, left or right (see section FREE FUNCTIONS, below), or an exception will be thrown. When redefining column specifications (e.g., when inserting FMT objects for previously defined columns) then the width of the wider column is used. Example:

// left align using 10 char. positions:
tab.fmt() << FBB::left(10);
// 1st col now right aligned, but its
// width remains 10
tab.fmr() << FBB::right(4);

CSVTabDef &operator<<(CSVTabDef &tab, Type const &value):
This operator is defined for the template type Type parameter value, where Type values must be insertable in std::ostreams. The (trimmed) width of value when inserted into an ostream defines the width of the next column, which is right-aligned. As width the previous insertion operator: if a previous definition specified a larger width, then that width is kept. Example:

// 2 columns, having widths 2 and 5:
tab.fmt() << 12 << "hello";

Inserting the table’s elements

In addition to the insertion operator actually inserting a value into the next table’s column(s) several format modifying insertion operators are available. When a series of specifications are inserted before the actual value is inserted then the specification inserted just before inserting the table’s value is used, overruling that column’s default specification. Format specifications other than those provided by the standard I/O manipulators are ignored when used beyond the table’s last column.

The return types and left-hand side operands of the following insertion operators use CSVTabIns objects. CSVTable’s conversion operator operator CSVTabIns() described below returns a CSVTabIns object which is used by the following insertion operators to insert values into the table.

CSVTabIns &operator<<(CSVTabIns &tab, FMT::hline):
This operator inserts a horizontal line in the table’s next column element. It is ignored when used beyond the table’s last column;
CSVTabIns &operator<<(CSVTabIns &tab, (*FMT::hline)(unsigned nColumns)):
This operator inserts a horizontal line spanning the next nColumns columns of the table. If the argument nColumns is omitted then a horizontal line is inserted spanning all of the table’s remaining columns. When covering multiple columns no separators are used between the columns containing horizontal lines but one continuous horizontal line is used instead. The horizontal line is never written beyond the table’s last column.
CSVTabIns &operator<<(CSVTabIns &tab, Type const &value):
This operator is defined for the template type Type parameter value, where Type values must be insertable in std::ostreams. The value is inserted into the next table column, using the format specification that’s active for that column. However, the specifications may be altered just before inserting the value. Values inserted beyond the table’s last column are inserted as-is (although standard I/O manipulators can still be used);
CSVTabIns &operator<<(CSVTabIns &tab, FMT const &fmt):
FMT objects are returned by several free functions defined in the FBB namespace (i.e., center, left, or right, described below in section FREE FUNCTIONS). Example:

// left align using precision 2. E.g.,
// e.g., ’12.13 ’
tab << left(2) << 12.1278;

CSVTabIns &operator<<(CSVTabIns &tab, FMT::Align align):
The alignment argument can be FMT::CENTER, FMT::LEFT or FMT::RIGHT. Example:

// centers ’12’ in its column,
// e.g., ’ 12 ’
tab << FMT::CENTER << 12;

void operator<<(CSVTabIns &tab, std::ios_base &(*func)(std::ios_base &)):
This insertion operator accepts manipulators like std::left and std::right. When inserting these manipulators the next value to insert into the table is manipulated accordingly, overruling the next column’s default specification. Example:

// ’hi’ is left-aligned, using the
// using the default width and precision
tab << std::left << "hi";

CSVTabIns &operator<<(CSVTabIns &tab, Sep const &sep):
The separator used when starting to insert values into the table’s next row is changed to the separator specified by sep. It remains active for the table’s current row, also when inserting values beyond the table’s last column. Example:

// writes, e.g., ’one, hi there’
tab << "one" << FMT::Sep{" "} << "hi" << "there";

operator CSVTabIns():
The conversion operator returns a CSVTabIns object which is used in combination with the above insertion operators to insert values into the next row of the table. Normally insertions start at column 1, but when called after calling tab.more (see below) then insertions continue after the last element that was inserted into tab.more. Each time this conversion operator is used another row is added to the table. Insertions beyond the table’s last column are processed, but CSVTabIns’s insertion operators are ignored, inserting values as-is. However, in that case the standard std::ostream manipulators can also be used.
void operator()(std::string const &text):
Calls text, 0 to insert the trimmed comma-separated elements of text into the table’s next row;
FMT const &operator[](unsigned idx) const:
Returns the default FMT specification of column idx (see also the description of the member size() below).

MEMBER FUNCTIONS

In the provided examples tab refers to an existing CSVTable object.

std::vector<FMT> const &columns() const:
Returns a reference to the vector containing the format specifications of the table managed by CSVTable;
CSVTabDef &fmt(unsigned idx = 0):
The elements inserted into the CSVTabDef object returned by fmt() define the specifications of the table’s columns. Specifications start at column offset idx, using 0 if not specified (its argument may not exceed the number of already defined columns or an exception is thrown). When called repeatedly for already specified columns then the widths of existing columns are kept if they exceed the widths of the corresponding inserted FMT elements. Repeated fmt calls may specify more columns than previous calls, in which case new columns are added to the table.
void fmt(std::string const &colSpecs, unsigned idx = 0):
The comma-separated space-trimmed words of colSpecs define the widths of right-aligned table columns, starting at column index idx, using 0 if not specified (its argument may not exceed the number of already defined columns or an exception is thrown). When called repeatedly for already specified columns then the widths of existing columns are kept if they exceed the lengths of the corresponding trimmed words. Repeated calls may specify more columns than previous calls, in which case additional columns are added to the table. Example:

// Define three right-aligned columns,
// having widths of 3, 3 and 5.
tab.fmt("one, two, three");
// add columns 4 thru 6
tab.fmt("one, two, three", 3);

unsigned idx() const:
The index of the column that will be used at the next insertion is returned. When inserting more values than the number of defined table columns then the return value of the member size is returned;
CSVTabIns more(unsigned idx = ~0U):
When the default idx argument is used then values that are inserted into the returned CSVTabIns object are inserted beyond the last-used column of the table’s current row (which may be the row’s first element).
When using another argument then insertions start in column idx. If dx exceeds the last-used column index then intermediate columns remain empty.
If idx is less than the column index that is used at the next insertion an exception is thrown.
Insertions beyond the table’s last column are processed, but then CSVTabIns’s insertion operators are ignored, inserting values as-is. However, in that case the standard std::ostream manipulators can also be used;
Following more the current row doesn’t end, but values inserted next are inserted into the same row. Example:

// a row containing one element:
tab << 1;
// the next row contains 2 elements:
tab.more() << 1 << 2;
// now containing 4 elements
// (element at idx 2 remains empty):
tab.more(3) << 4;
// completes the row, now having
// 5 elements:
tab << 5;

Following more calls the current row ends at the next tab.row call. If following more calls the current row should merely end then simply use tab.row();
void more(std::string const &text, unsigned idx = ~0U):
This member’s idx parameter is handled as described at the previous member.
The trimmed comma-separated elements of text are inserted into the current row, without ending the current row;
CSVTabIns row(unsigned idx = ~0U):
This member’s idx parameter and insertions into the returned CSVTabIns object are handled as described at the first more member, but the current row ends at the end of the statement. Example:

// a row containing one element:
tab << 1;
// the next row contains 2 elements:
tab.more() << 1 << 2;
// the now contains 4 elements
// (element at idx 2 remains empty):
tab.row(3) << 4;

void row(std::string const &text, unsigned idx = ~0U):
This member’s idx parameter is handled as described at the first more member.
The trimmed comma-separated elements of text are inserted into the current row, whereafter the row ends;
void stream(std::ostream &out):
After calling tab.stream(out) the table’s construction continues at the next row using the stream out;
void stream(std::ofstream &&tmp):
After calling this member the table’s construction continues at the next row using the ofstream tmp, whih is grabbed by CSVTable;
void stream(std::string const &fname, std::ios::openmode mode = std::ios::out):
After calling this member the table’s construction continues at the next row using the (path)name fname, by default (re)writing the file. If the file already exists and CSVTable should start writing at the file’s end use, e.g., ios::ate | ios::in. An exception is thrown if the specified file cannot be opened;
std::ostream &stream():
A reference to the currently used stream is returned;
std::string const &sep() const:
Returns the currently used default column separator;
void sep(std::string const &separator):
Changes the currently used default column separator to separator.
unsigned size() const:
The number of defined columns is returned;

FREE FUNCTIONS

In the following examples tab.fmt() refers to a CSVTabDef object.

next examples tab refers to a CSVTable object (using its conversion to a CSVTabIns object) and

Defining Column Characteristics

The following functions are used to specify the alignment, width and optional precision of columns. The first argument of these functions specifies the column’s width, the second argument is optional and specifies the column’s precision (used when inserting floating point values). The precision is only used if its value is less than the column’s width.

FMT center(unsigned width, unsigned precision = ~0U):
When inserting this function’s return value into tab.fmt() the values inserted into its column are centered in fields of width characters wide. Example:

// values are centered in fields of 10
// characters wide, floating point values
// use 3 digit behind the decimal point:
tab.fmt() << center(10, 3);

FMT center(std::string const &str, unsigned precision = ~0U):
A convenience function calling str.length(), precision ;
FMT left(unsigned width, unsigned precision = ~0U):
When inserting this function’s return value into tab.fmt() the values inserted into its column are left-aligned in fields of width characters wide. Example:

// values are left-aligned in fields
// of 5 characters wide.
tab.fmt() << left(5);
FMT left(std::string const &str, unsigned precision = ~0U):
A convenience function calling left(str.length(), precision);
FMT right(unsigned width, unsigned precision = ~0U):
When inserting this function’s return value into tab.fmt() the values inserted into its column are right-aligned in fields of width characters wide. Example:

// values are right-aligned in fields
// of 5 characters wide.
tab.fmt() << right(5);
Right-alignment is also used when using CSVTab’s fmt(std::string) member or when directly inserting values into CSVTabDef objects.
FMT right(std::string const &str, unsigned precision = ~0U):
A convenience function calling right(str.length(), precision);

Inserting Table Elements

In the following examples tab refers to a CSVTable object returning a CSVTabIns object using its conversion operator.

Except for the function hline the following functions are used to alter the column’s default alignment and precision. The precision is only used if its value is less than the column’s width. By specifying ~0U the precision is ignored. If only the default alignment should be overruled then inserting the corresponding FMT::Align value suffices.

Altering the default alignment of individual columns:

FMT precision :
After inserting this function’s return value into tab the value inserted next is centered, using precision when inserting floating point values.

// centers 9.87 in column 1
tab << center(2) << 9.876";

FMT left(precision):
After inserting this function’s return value into tab the value inserted next is left-aligned, using precision when inserting floating point values.

// left-aligns 9.87 in column 1
tab << left(2) << 9.876";

FMT right(precision):
When inserting this function’s return value into tab the value inserted next is right-aligned, using precision when inserting floating point values.

// right-aligns 9.87 in column 1
tab << right(2) << 9.876";
By default CSVTable uses right-alignment.

Joining columns:

Alignments specifications may span multiple columns. This is realized through the join functions. When inserting a value after inserting the return value of a join member then that value is inserted occupying all the columns and using the alignment type specified when calling join. If necessary the number of columns is reduced to avoid exceeding the table’s last column.

FMT join(unsigned nCols, FMT::Align align, unsigned precision = ~0U):
A value that’s inserted into the table after inserting join’s return value occupies nCols columns, using alignment type align, and optionally using precision when inserting floating point values. The alignment specification must be FMT::CENTER, FMT::LEFT or FMT::RIGHT. Example:

// writes (assuming columns 2 and 3 occupy
// 10 characters):
// left, mid , right
tab << "left" << join(2, FMT::CENTER) << "mid" << "right"";

FMT join(FMT::Align align, unsigned precision = ~0U):
Same effect as the previous join function, but this function occupies all remaining columns of the table’s current row (this can also be accomplished by calling the first join function specifying ~0U as its first argument).

Inserting horizontal lines:

If a single table element should contain a horizontal line then simply inserting Align::HLINE works fine. The hline functions are used to insert horizontal lines spanning one or more table columns.

FMT hline(unsigned nCols = ~0U):
When inserting this function’s return value into a CSVTabIns object a horizontal line spanning nCols columns is inserted into the table. If necessary nCols is reduced so that the horizontal line does not exceed the table’s last column. When spanning multiple columns no column separated are used between the spanned columns: a single uninterrupted horizontal line is inserted. Example:

// columns 1 and 2: a horizontal line, column 3:
// contains ’hi’ (preceded by the column separator)
tab << hline(2) << "hi";

EXAMPLE

#include <bobcat/csvtable>
using namespace FBB;
int main()
{

CSVTable tab;
tab.fmt() << "case" << right("length", 2) << right("weight", 1) <<
right("length", 2) << right("weight", 1);
tab.sep(" ");
tab << hline();
tab << "" << join(4, FMT::CENTER) << "Gender";
tab << "" << hline();
tab << "" << join(2, FMT::CENTER) << "Female" <<
join(2, FMT::CENTER) << "Male";
tab << "" << hline(2) << hline(2);
tab << "Case" << "Length" << "Weight" << "Length" << "Weight";
tab << hline();
tab << 1 << 1.744 << 55.345 << 1.7244 << 64.801;
tab << 2 << 1.58 << 57.545 << 1.8174 << 81.451;
tab << 3 << 1.674 << 62.125 << 1.8244 << 80.201;
tab << hline(); }

This program writes the following table to std::cout:

------------------------------------

Gender
------------------------------
Female Male
-------------- -------------- Case Length Weight Length Weight ------------------------------------
1 1.74 55.3 1.72 64.8
2 1.58 57.5 1.82 81.5
3 1.67 62.1 1.82 80.2 ------------------------------------

FILES

bobcat/csvtable - defines the class interface

SEE ALSO

bobcat(7), table(3bobcat)

BUGS

None Reported.

BOBCAT PROJECT FILES

https://fbb-git.gitlab.io/bobcat/: gitlab project page;
bobcat_5.09.01-x.dsc: detached signature;
bobcat_5.09.01-x.tar.gz: source archive;
bobcat_5.09.01-x_i386.changes: change log;
libbobcat1_5.09.01-x_*.deb: debian package containing the libraries;
libbobcat1-dev_5.09.01-x_*.deb: debian package containing the libraries, headers and manual pages;

BOBCAT

Bobcat is an acronym of `Brokken’s Own Base Classes And Templates’.

COPYRIGHT

This is free software, distributed under the terms of the GNU General Public License (GPL).

AUTHOR

Frank B. Brokken (f.b.brokken@rug.nl).

2005-2021 libbobcat-dev_5.09.01