The RWP*Load Simulator has several features that make it suited for modular programming:
Your simulation should consist of a set of rwl input files potentially with inclusion of other files via the $include directive, which allows for modular development. One particular useful approach is using a single “master” file with inclusion of everything else needed. You could e.g. have files that contain database declarations, files that contain SQL and procedure declarations, and files that contain the actual simulation. Although possible, you are advised to only run one simulation (that is one thread execution using the run keyword).
Unless -no-nameexpand option or the $nameexpand:off directive is used, environment names in either $NAME or ${NAME} syntax will be expanded before opening files. This allows for advanced scripting.
As an alternative to having a long list of file names provided to rwloadsim, you can create one “master” file that includes other files using $include directives. Such files can themselves contain $include directives for multiple levels of inclusion. You can only use $include when you are not parsing a statement, declaration or thread execution and the file included must similarly contain complete rwl syntax. The file name to be included is either put between double quote characters or between ‘<’ and ‘>’ characters similar to how it is done in C. In the first case, the file will first be attempted opened in the current directory, then in the directories provided in the RWLOADSIM_PATH environment variable. Using the -u option, the public directory will be searched before any directories mention in RWLOADSIM_PATH. In the latter case, the current directory will not be searched, instead, the file will be searched in the public directory and then in the directories mentioned in RWLOADSIM_PATH.
Environment variable expansion takes place as it does for files name on the command line.
You can use the three directives $if $then, $else, $endif similar to how #if, #else, #endif are used in C to conditionally include or exclude code. The $if … $then directive takes a simple expression that does not include function calls (neither most standard functions nor user defined functions); the simplified expression must be between $if and $then and all of these three parts must be on the same source line. If the expression is non-zero, the code until a subsequent $else is included, otherwise the code after $else and until $endif is included. The $else part can be omitted.
The expression that is between the $if and $then directives can only consist of constants or global or public variables of type integer, double or string (including environment variables such as $USER), the function access() or the function defined(), which takes an identifier as its single argument. No other standard or declared functions can be used.
Some examples are shown here:
integer one := 1;
$if one $then
# This code is included
printline "this will be printed";
$else
# This code is not included
$include:"subfile.rwl"
$endif
$if one-1 $then printline "nothing will be printed"; $endif
$if defined(one ) $then
printline "one="||one;
$endif
$if $PRECISION="high" $then $dformat:%.8f $endif
printline "sqrt(2) =", sqrt(2);
If the above is given to rwloadsim with PRECISION=high in the environment, what really will be parsed is only the following:
# This code is included
printline "this will be printed";
printline "one="||one;
printline "sqrt(2) =", sqrt(2);
The file named ‘subfile.rwl’ will not be recursively read and the last printline will not be included.
The $dformat directive will be processed only if the environment variable $PRECISION has the value “high”, causing the last printline to show the square root of 2 with 8 digits precision.
Note the following points about these directives:
One potential use-case for these directives is to comment out large parts of code by surrounding if with $if 0 $then and $endif
The rwloadsim program cannot read code to be executed from stdin, so you cannot use something like <<END in a shell script. To achieve a similar effect, you can use the –execute-code option, which takes a single shell token containing rwl code. For example
rwloadsim --quiet --execute-code '
$mute:99
double a;
for a := 1.0..20.0 loop
printline a, sqrt(a), log(2,a);
end loop; '
will display a list of numbers from 1 until 20, their square root, and their base 2 logarithms. The $mute:99 directive is included to prevent the warning about missing input files.