RE: Call-by-reference from inside a function
- To: mathgroup at smc.vnet.net
- Subject: [mg72573] RE: [mg72568] Call-by-reference from inside a function
- From: "David Park" <djmp at earthlink.net>
- Date: Wed, 10 Jan 2007 02:38:56 -0500 (EST)
Give your function the Attribute HoldFirst. David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: zac [mailto:replicatorzed at gmail.com] 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]