Re: Call-by-reference from inside a function

*To*: mathgroup at smc.vnet.net*Subject*: [mg72587] Re: [mg72568] Call-by-reference from inside a function*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Wed, 10 Jan 2007 03:35:11 -0500 (EST)*References*: <200701091249.HAA21706@smc.vnet.net>

If I understand you correctly, all you need is something like this: s = {1, 2, 3, 4}; SetAttributes[f, HoldAll] f[p_] := Module[{i = Random[Integer, {1, Length[p]}]}, p = Drop[p, {i}]] f[s] {2, 3, 4} f[s] {2, 3} Andrzej Kozlowski Oxford, UK On 9 Jan 2007, at 12:49, zac wrote: > Dear Group, > > I'm in need of a function, which is called with one argument, a list. > The function is to chose one element of the list randomly, AND modify > the original list by removing the chosen element from it. My > problem is > that I cannot modify the global variable from inside the function. It > is not a solution to return with a list such as: > Return[{chosen_element, modified_local_list}], and than make an > assignment outside the function. > I'm thinking on some call-by-reference method, but as I've learned so > far, there is no user-friendly way to do this, just some workarounds > (which I don't know). Any suggestions? > > Istvan > > example code below: > > RandomChoseElem[list_List] := Module[ > {pos, elem}, > pos = Random[Integer, {1, Length[list]}]; > elem = list[[pos]]; > (* This is to be solved inside : *) > (* global`list = Drop[global`list, {pos}]; *) > Return[elem] > ]; > > set = {1, 2, 3, 4}; > > RandomChoseElem[set] >

**References**:**Call-by-reference from inside a function***From:*"zac" <replicatorzed@gmail.com>