Editing MultiLisp (section)

==PCALL and FUTURE==
MultiLisp achieves parallelism with the PCALL [[Macro (computer science)|macro]], where

<code>(PCALL Fun A B C ...)</code>

is equivalent to

<code>(Fun A B C ...)</code>

except that the [[Parameter (computer programming)|argument]]s <code>A, B, C,</code> etc. are explicitly allowed to be evaluated in parallel; this circumvents the usual order of evaluation, which is sequential and left to right. It also makes use of a parallel programming construct called [[Future (programming)|futures]], which resembles [[Fork (system call)|forking]], combined with [[lazy evaluation]]. Using this construct, an expression such as

<code>([[cons]] (FUTURE A) (FUTURE B))</code>

can be written, which will overlap the evaluation of the expressions A and B, not only with each other, but with computations that use the result of the [[cons]] call, until an operation is performed that needs correct information about the value of A or B.