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02/23/2010 CPSC 449 Computer Science Unless otherwise noted, all artwork and illustrations by either Rob Kremer or Jörg Denzinger (course instructors) Prolog Structuring Programs 306 2015/01/05 CPSC 449 Structuring programs ■ While in theory the rules (clauses) with a particular predicate as head can be distributed over several files that are consulted by the interpreter to load everything required by a program, naturally the sequence in which these rules end up in the data base will have a big impact on the program ■ Therefore it is a good practice to cluster the rules with a particular head in one file and also within this file • GNU Prolog forces clustering of rules (except if you use the directives discontiguous/1 or multifile/1) 307 2015/01/05 CPSC 449 PROLOG program structure ■ There really is not much of a structure required in PROLOG programs, most of the structure we see in books or real programs is voluntary by the programmer ■ In most PROLOG versions there are -No modules -No types and type declarations -No particular layout ■ The only real conventions are that every rule ends with a ".", that atoms are separated by "," and that ";" indicates an "or" in the body of a rule 308 02/23/2010 CPSC 449 Computer Science Unless otherwise noted, all artwork and illustrations by either Rob Kremer or Jörg Denzinger (course instructors) Prolog Executing Programs 309 2015/01/05 CPSC 449 Executing programs ■ PROLOG is usually an interpreted language, although there are compilers that compile in bytecode for the Warren Abstract Machine (Java got the idea of the Java Virtual Machine from there) ■GNU Prolog is compiled for WAM. ■ A PROLOG program is usually loaded into the interpreter's data base using the consult/1 predicate ■ consult/1 expects as argument a file name and the exact format depends on the machine the interpreter runs on (on our machines you need consult('myfile').) 310 2015/01/05 CPSC 449 Executing programs ■ GNU Prolog can be “scripted” by adding the line: #!/opt/local/bin/gprolog —consult-file as the first line of the Prolog file. • “#” is treated as a comment if it’s the first line of a file. • UNIX interprets the file with the “shebang” protocol. 311

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02/23/2010 CPSC 449

Computer Science

Unless otherwise noted, all artwork and illustrations by either Rob Kremer or Jörg Denzinger (course instructors)

PrologStructuring Programs

306

2015/01/05 CPSC 449

Structuring programs

■While in theory the rules (clauses) with a particular predicate as head can be distributed over several files that are consulted by the interpreter to load everything required by a program, naturally the sequence in which these rules end up in the data base will have a big impact on the program ■Therefore it is a good practice to cluster the rules

with a particular head in one file and also within this file • GNU Prolog forces clustering of rules (except if you use

the directives discontiguous/1 or multifile/1)

307

2015/01/05 CPSC 449

PROLOG program structure

■There really is not much of a structure required in PROLOG programs, most of the structure we see in books or real programs is voluntary by the programmer ■ In most PROLOG versions there are

-No modules -No types and type declarations -No particular layout

■The only real conventions are that every rule ends with a ".", that atoms are separated by "," and that ";" indicates an "or" in the body of a rule

308

02/23/2010 CPSC 449

Computer Science

Unless otherwise noted, all artwork and illustrations by either Rob Kremer or Jörg Denzinger (course instructors)

PrologExecuting Programs

309

2015/01/05 CPSC 449

Executing programs

■PROLOG is usually an interpreted language, although there are compilers that compile in bytecode for the Warren Abstract Machine (Java got the idea of the Java Virtual Machine from there)

■GNU Prolog is compiled for WAM.

■A PROLOG program is usually loaded into the interpreter's data base using the consult/1 predicate ■consult/1 expects as argument a file name and the

exact format depends on the machine the interpreter runs on (on our machines you need consult('myfile').)

310 2015/01/05 CPSC 449

Executing programs

■GNU Prolog can be “scripted” by adding the line: #!/opt/local/bin/gprolog —consult-file as the first line of the Prolog file. • “#” is treated as a comment if it’s the first line of a file. • UNIX interprets the file with the “shebang” protocol.

311