164 Examples of the first type (see figure~\ref{fullapplication}) are Parc Technologies applications (http://www.parc-technologies.com) like AirPlanner\index{AirPlanner} and RiskWise\index{RiskWise}\footnote{In the following we use a number of examples from the RiskWise application. It is a network analysis tool for IP networks, which uses a constraint solver to determine traffic pattern in the network. If this doesn't make any sense to you, relax. An understanding of the networking application domain is not required to follow this tutorial.}, where everything except the problem solver is developed in Java\index{Java} or related tools. The interface between the main application and the problem solver written in ECLiPSe is via a Java-ECLiPSe interface. In this interface, the main application poses queries for the ECLiPSe solver, passing data and arguments into ECLiPSe. The problem solver then runs the query and returns results as variable bindings in the given query. The Java side only knows about these queries, their data format and the expected results. The internals of the solver, how the queries are resolved, is completely hidden. This defines a nice interface between the application parts, as long as the queries are well defined and documented. Once that design is frozen, the developers for the different parts can continue development independently from each other, using stubs or dummy routines to simulate the other application parts. 
234 \item[create variables] This is followed by the variable generation, where we create all variables that will be used in the solver. These variables will simply be placed in slots already provided in the data structures.
329 Variable names \index{variable name}\index{name, variable}are of form [A-Z\_][a-zA-Z]*[0-9]* . Separate words start with capital letters. Digits should only be used at the end. Words should be English. If a variable occurs only once in a clause, then its name should start with an underscore\index{underscore}. This marks it as a {\it singleton variable}\index{singleton variable}, and stops compiler warnings about the single occurrence of a variable. If a variable occurs more than once in a clause, then its name should not start with an underscore.
501 \index{placeholder variables}If we do not specify a fixed attribute value when the named structure is created, then its value will be a free variable which can be bound later on. This is useful for two main purposes. On one side we can define attributes of a structure which will hold the constraint variables\index{constraint variables} of a problem, on the other side we can leave some attributes initially unassigned so that we can fill these slots with results of a computation later on.
558 It is tempting to ignore warnings in order to get the code running as quickly as possible. That would be a big mistake. We should eliminate all warnings about singleton variables\index{singleton variable} and missing predicate \index{missing predicate}definitions before continuing. Not only will this lead to the detection of problems in the code at this point, we will also immediately see if new warnings are introduced when we change some part of the program. 
618 should be added as a singleton variable.
713 Very often, we have to pass additional parameters into the {\it do} loop. We do this with the {\it param}\index{param} parameter, which lists all variables from outside the loop that we want to use inside the loop. A variable which is not mentioned as a {\it param} argument, is unbound inside the loop. Normally, this will create a warning about a singleton variable\index{singleton variable} inside a {\it do} loop. The following code fragment shows the use of {\it param} to pass variables $A$, $B$ and $C$ to the call of predicate {\it q}.
822 Note the strange way in which parameters $M$, $I$ and $Matrix$ are passed through the nested {\it for} loops with {\it param} arguments. But if we do not do this, then the variable $Matrix$ outside and inside the {\it do} loop are unrelated.
847 \item[K] a free variable, will be bound to a list
886 Figuring out what is happening with the variable {\it Router} is left as an exercise for the advanced reader.
896 \item[K] a free variable, will be bound to a list
984 \item[Res] a free variable, will be bound to a list
1048 \item[V] a free variable, will be bound to an entry of $L$
1075 \item[Best] a free variable, will be bound to an entry of $L$
1076 \item[Rest] a free variable, will be bound to a list of the entries of $L$ without $Best$
1127 \item[Sum] a free variable, will be bound to a value
1249 \item[K] a free variable, will be bound to a list
1300 \item[Res] a free variable, will be bound to a list
1373 \item[Res] a free variable, will be bound to a list
1438 \item[K] a free variable, will be bound to a list
1726 Run-time errors\index{run time error}\index{error, run time} occur if we call a built-in predicate with a wrong argument pattern. This will usually either be a type mismatch\index{type mismatch}, i.e. using a number where an atom is expected, or an instantiation problem, i.e. passing a variable where a ground value was expected or vice versa. In this case the ECLiPSe system prints out the offending call together with an error message\index{error message} indicating the problem. If we are lucky, we can identify the problem immediately, otherwise we may have to look up the documentation of the built-in to understand the problem.
1746 \item If the call to the predicate contains some variable name, we may be able to locate the problem by searching for that name in the source file(s). 
1933 \item  Variable names\index{variable name} are of form [A-Z\_][a-zA-Z]*[0-9]* . Separate words star with capital letters. Words should be English. The plural should be used for lists and other collections. Digits should only be used at the end to distinguish different versions of the same conceptual thing.
1971 \item  local variable definitions 
2222 \item[var/1] \index{var/1}argument is a variable

Indexes created Sat Jul 27 18:59:09 MDT 2024