Re: Sequential evaluation of lists

*To*: mathgroup at smc.vnet.net*Subject*: [mg53108] Re: [mg53076] Sequential evaluation of lists*From*: yehuda ben-shimol <benshimo at bgu.ac.il>*Date*: Thu, 23 Dec 2004 07:59:50 -0500 (EST)*References*: <200412220953.EAA04525@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

The evaluation is not always left to right. There are some cases that it goes from right to left, and it SHOULD do so. L2R evaluation {Print[a], Print[b], Print[c]}; results with a b c R2L evaluation Print[d] & /@ {Print[e]} & /@ {Print[f]} and get f e d {{Null}} For your specific case (and others as well) of x=0;{x++,x++,x++} you can use Trace to follow the evaluation order x=0;Trace[{x++,x++,x++}] and get {{x++, {x, 0}, {x = 1, 1}, 0}, {x++, {x, 1}, {x = 2, 2}, 1}, { x++, {x, 2}, {x = 3, 3}, 2}, {0, 1, 2}} or Trace[{a=1,b=2,c=3}] and get {{a = 1, 1}, {b = 2, 2}, {c = 3, 3}, {1, 2, 3}} yehuda Ray Koopman wrote: >When I first started using Mathematica (v2), one of the features that >I found rather surprising is its sequential evaluation of lists, as in > >In[1]:= x = 0; {x++,x++,x++} >Out[1]= {0,1,2} > >I had expected a warning that such code should be avoided because >it presumed sequential evaluation, which could not be guaranteed, >and a recommendation to treat list elements as being evaluated in >parallel -- if not simultaneously then in no particular order. >However, so far I have found no exception to sequential evaluation >and no mention of it in any documentation. Have I missed something? > > >

**Follow-Ups**:**Re: Re: Sequential evaluation of lists***From:*DrBob <drbob@bigfoot.com>

**References**:**Sequential evaluation of lists***From:*"Ray Koopman" <koopman@sfu.ca>