src/swipl-devel/packages/xpce/man/refmanual/md/block.md

In rswipl: Embed 'SWI'-'Prolog'

class block {#class-block}

A block object defines a sequence of code objects with a formal parameter list.

On ->forward, the var objects in <-parameters will be bound to the forwarded arguments (exceeding arguments are bound to @arg1 ...) and the <-members statements of the block are executed just as with the super-class and.

Example:

?- send(block(new(X, var),
              message(@pce, write_ln, X)),
        forward,
        'Hello World').

Hello World.

@see class ?

Instance variables {#class-block-instvars}

• block<->parameters: code_vector* Vector with formal parameters. Assigned (see var->assign) by ->forward.

Send methods {#class-block-send}

• block->forward: any ... When a block object is forwarded, it will bind the arguments to the var objects in <-parameters by position. Possible exceeding arguments are bound to @arg1 ... for compatibility reasons. Next the block is ->execute'd just like the and object.

  Example:

  ?- send(chain(chain(a,b), chain(c,d)), for_all,
          block(new(Sub, var),
                message(Sub, for_all,
                message(@pce, write_ln, Sub, @arg1)))).
  

rswipl documentation built on June 16, 2026, 5:07 p.m.