Dynamic Prolog clause-body generation

开发者_开发技巧For an assignment I have to generate a prolog procedure body dynamically. How can I do this?

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See here for the swi prolog manual description of relevant predicates.

As an example consider the following

goal :- Z =.. [foo, 1], 
    Y =.. [bar,2], 
    X =.. [',', Z, Y], 
    R =.. [':-', r, X],  
    assert(Z), assert(Y), assert(X), assert(R).

PS: Another possibility is lower class, but sometimes can be a better choice: just print out what you need to construct to a file.

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to add a predicate you need to use asserta/1 or assertz/1 (assert/1 is deprecated) more if you have already declared some of the clauses of the predicate in the code you loaded you should define the predicate as dynamic using dynamic/1 more

forming the clause depends on the form of the input. if you have a list with the name of the predicate and the arguments you can use =../2 if you have the clause on a string you can use term_to_atom/2 (it works both ways)

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assert/1, asserta/1, retract/1, retractAll/1, abolish/1

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You can generate dynamic predicate with '(' and ')' enclosing body.

assert(test(X):- (X1 is X+1,  write(X1)))