Conditions

Syntax

Condition =
     Source Rest.

Evaluation

The evaluation of a path S R proceeds as follows. The source S is evaluated, and, if the evaluation succeeds, the rest R is evaluated.

The source S is considered to be at the zero level.

     Env,0,St |- S => ,St'
     Env,m,St'|- R => X,St''
     -------------------------
     Env,m,St |- S R => X,St''


     Env,0,St |- S => $fail(k),St'
     -------------------------------
     Env,m,St |- S R => $fail(0),St'


     Env,0,St |- S => $error(Ge),St'
     ---------------------------------
     Env,m,St |- S R => $error(Ge),St'