![]() ![]() This means that the two variables SourceCode and SOURCECODE are the same. The Visual Prolog compiler does not make a distinction between upper and lower case letters in names, except for the first letter. That is, if two clauses each contain a variable called X, these X-s are two distinct variables.Ī variable is said to be free when it is not yet associated with a term and to be bound or instantiated when it is unified with a term. Prolog variables are local to the clause in which it occurs. The compiler will issue a warning if the value of such a warning is actually not ignored. If variables that starts with an underscore are not anonymous, but they are still intended for values of no interest that should be ignored. even though the anonymous variable is used several times in a single clause they have no relation to each other. ![]() Every occurrence of the anonymous variable is an independent anonymous variable, i.e. The anonymous variable is used in patterns and bindings where the corresponding value is of no interest and should be ignored. ![]() The variable consisting of single underscore character (i.e. The mechanism will be described and exemplified in details in the following sections. Thereby restoring the program state and pursuing the other choice. if it fails), then the program will backtrack to the recorded backtrack point. If it turn out that the original choice could not provide the solution (i.e. A backtrack point is a recording of the program state plus a pointer to the choice that was not executed. When such a choice point is met a so called backtrack point is created. At certain points in the program execution there are more than one possible choices for finding a solution. Each step in the search for a solution can either succeed or fail. The evaluation of a Prolog program is a search for a "solution" to the goal.
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