The procedural part of the rwl language has several types of compound statements known from
other programming languages.
These all begin with a keyword that identifies the type procedural construct and
are terminated by the keyword end optionally followed be the beginning keyword.
Compound statements can be nested.
The if statement is used to execute one of many branches of code.
It starts with the keyword if followed by an expression and the keyword then;
if the expression is non zero, the list of statements after then will be executed.
You can have multiple branches by starting subsequent branches with elseif,
expression and then, and
you can have a branch that gets executed if no other branches do using else.
This first example will execute the printline statement if the value 42 has been read from stdin:
integer theanswer;
readline stdin,theanswer;
if theanswer=42 then
printline "You have found the answer";
end if;
The next example shows the use of both elseif and else clauses:
integer theanswer;
readline stdin,theanswer;
if theanswer <= 40 then
printline "Your answer is too low";
elseif theanswer=41 or theanswer=43 then
printline "Close but no cigar";
elseif theanswer=42 then
printline "That really is the answer";
else
printline "You have come too far";
end if;
The while loop executes a list of statements as long as some condition is non-zero. A simple example is:
integer theanswer := 37;
while theanswer < 42 loop
printline theanswer " is not yet found";
theanswer += 1;
end loop;
printline "You found it:" theanswer;
Several loops start with the keyword for and one of them is a loop that simply
increases a variable by 1 for each execution of the loop.
The syntax consists of the for keyword followed by an assignment and the list of values
to loop through separated by .. and finally the keyword loop
This example shows it:
integer theanswer, lo, hi;
lo := 40; hi:= 44;
for theanswer := lo .. hi loop
if theanswer = 42 then
printline "You have found the answer";
else
printline "The answer is not " theanswer;
end if;
end loop;
The purpose of the execution block is simply to wrap a list of statements and it is mostly useful
when that list of statement must be executed against the same database session.
The keyword execute potentially followed by an at clause starts the list of statements as this example shows:
execute at mydb
sql myinsert ...
end;
myinsert;
commit;
end;
Rwloadsim also includes loops that read lines from a file, fetch rows from a cursor and control execution in typical simulations.