.TH tabletostruct "" "" "/rdb Command"
.PC "Convert table to C-language struct declaration"
\fBtabletostruct \fItag name\fB < \fItable \fB> \fItable\fB.h\fR
.PP
.II struct
.II "table^convert to C struct"
.II "C language^struct"
The command
.B tabletostruct
converts a standard
.B /rdb
table into a C-language
.B struct
declaration.
.B struct
is the C language's record format.
.PP
.B tabletostruct
is useful for writing table-driven C code.
The tables used by your programs can be manipulated
by the data base and your users, or by nonprogrammer developers
(engineers, experts, managers, operators),
then converted to a
.B struct
and compiled into the C code for high-speed access.
.PP
.I tag
gives the
.B struct
tag for declaring other variables.
.I name
is the
.B struct
name to reference the structure values.
.PP
Please note once code compiled from a table,
changing that tables no longer affects the program until you recompile it.
Therefore, you gain maximum speed at the price of
recompiling the system and losing the flexibility of being
able to modify the tables during execution.
.SH Example
Here we start with a simple table, convert it to
.B struct,
make it a header file, and
compile it into a simple program that prints out each field.
To begin, consider table
.BR table ,
which is structured as followed:
.DM
A       B       C
-       -       -
1       2       3
.DE
.PP
The following commands converts
.B table
to a
.B struct
and writes it into file
.BR table.h :
.DM
	tabletostruct Table table < table > table.h 
.DE
.PP
.B table.h
now holds the following:
.DM
struct Table
{
char    *A;
char    *B;
char    *C;
}       table [] =
{ "1","2","3" }
;
.DE
.PP
The following gives some C code that prints the contents of the
.B struct
we call
.BR Table :
.DM
#include "table.h"
.sp \n(pDu
main ()
{
        printf ("A=%s\en", table[0].A);
        printf ("B=%s\en", table[0].B);
        printf ("C=%s\en", table[0].C);
}
.DE
.PP
When compiled with the command
.DM
        cc -o printtable printtable.o
.DE
.PP
the newly created command
.B printtable
yields the following output:
.DM
	A=1
	B=2
	C=3
.DE
.PP
Note that the data are stored in an array of
.BR struct s,
so we must give a subscript for each row we want.
.PP
We can also put the command
.B tabletostruct
into a
.BR Makefile ,
so that the COHERENT command
.B make
can automate the building of the
.B struct
and its compilation.
For example:
.DM
printtable:     table.h printtable.o
        cc -o printtable printtable.o
.sp \n(pDu
table.h:        table
        tabletostruct Table table < table > table.h
.DE
.PP
This says that the printable program depends upon
.B table.h
being up to date, and
.B table.h
depends upon table
.B table
being up to date.
If you had modified
.B table
since the last compile,
.B make
reexecutes the command
.BR tabletostruct .
.SH "See Also"
.B
listtotable,
tabletolist
.R
.br
COHERENT Tutorials:
.B
The C Language,
The make Programming Discipline
.R
.br
COHERENT Lexicon:
.B
array,
make,
struct
.R