if performs a single test and executes the associated command if the test is true:

if (backSensorM > 0) {
       pressed = 1;
       echo "Back sensor pressed";
};

Note that the last command between brackets doesn't need to be ended by a semicolon like in the above example. This is because semicolons are command separators and not command terminators. You can put a semicolon at the end like in C, but it is not required and it has not effect (it adds an empty command).

if (distance < 10)
  echo "Obstacle detected"
else
  echo "No obstacle";
[167322:notag] *** No obstacle

Note that, unlike in C, there is no semicolon before else, but there is a semicolon (or any other command separator) after the concluding }.

distance and backSensorM are two Aibo devices related to the head infrared distance sensor and to the middle (M) back sensor.

The while construct is similar to what is available in C:

i=0;
while (i<=2) {
  i:echo i;
  i++;
};
[151228:i] *** 0
[151228:i] *** 1
[151228:i] *** 2

The for construct is similar to what is available in C:

for (i=0;i<=2;i++)
  i:echo i;
[151228:i] *** 0
[151228:i] *** 1
[151228:i] *** 2

Unlike in C, URBI has specific constructs to handle parallel and serial loops: for&, for| and while|. These constructs will start every iteration in parallel (with &) or in series (with |) with a guaranteed time constraint. More details are available in the URBI Language Specification.

As we already mentioned before, there is also a foreach and foreach& construct to iterate lists:

foreach i in [0,1,2] {
  i:echo i;
};
[151228:i] *** 0
[151228:i] *** 1
[151228:i] *** 2

foreach is an exception: even when the iterated command is a single command, like in the above example, you must enclose it between brackets.

For practical reasons, URBI has added two more constructs, loop and loopn to create infinite loops in the first case and loops iterating n times in the second case. The syntax is:

loop { ... }

and

loopn (n) { ... }