

   DDeellaayy EEvvaalluuaattiioonn

        delay(expr, env=.GlobalEnv)

   AArrgguummeennttss::

       expr: an expression.

        env: an evaluation environment

   DDeessccrriippttiioonn::

        `delay' creates a promise to evaluate the given expres-
        sion in the specifies environment if its value is
        requested.  This provides direct access to lazy evalua-
        tion mechanism used by R for the evaluation of (inter-
        preted) functions.

        This is an experimental feature and its addition is
        purely for evaluation purposes.

   VVaalluuee::

        A promise to evaluate the expression.  The value which
        is returned by `delay' can be assigned without forcing
        its evaluation, but any further accesses will cause
        evaluation.

   EExxaammpplleess::

        x <- delay({
            for(i in 1:7)
                cat("yippee!\n")
            10
        })

        x^2#- yippee
        x^2#- simple number

