RE: Assignments

*To*: mathgroup at smc.vnet.net*Subject*: [mg36388] RE: [mg36295] Assignments*From*: "DrBob" <drbob at bigfoot.com>*Date*: Wed, 4 Sep 2002 02:56:46 -0400 (EDT)*Reply-to*: <drbob at bigfoot.com>*Sender*: owner-wri-mathgroup at wolfram.com

>>But my actual output reproduces the input form, i.e., it is simply f[...listA,newEntry,...]. That means your arguments don't fit a pattern for which the function is defined. That is, it has nothing to do with what's on the right side of ":=". It's about making sure there are the right number and type of arguments passed to the function. You haven't told us what the pattern is or what the arguments are, so we can't help you. Bobby -----Original Message----- From: Thomas J. Fararo [mailto:tjf2+ at pitt.edu] To: mathgroup at smc.vnet.net Subject: [mg36388] [mg36295] Assignments Hello, I am fairly new to Mathematica and once before asked a question and received some very helpful responses. This time the problem seems very odd and I may be making a very elementary error. Here is the context: I define a function of the form: f[...,listA_, newEntry_,...]:= Which[...] Here Which has the form of a set of logically exclusive and exhausive tests, each test with its own action that modifies the concrete list subsituted for listA_. For instance, if there were only two tests the rhs above would be one that puts the newEntry at the start of listA and the other that puts it at the end: Which[ test1, listA = Insert[listA, newEntry, 1], test2, listA = Insert[listA, newEntry, -1] ] Then I try to use the function, substituting values for the arguments: f[..., listA, newEntry, ...]. The output should be the appropriately modified list. But my actual output reproduces the input form, i.e., it is simply f[...listA,newEntry,...]. Yet, the program does do something, as the use of "evaluate in place"shows: Suppose that test1 is satisfied by the particular values of the arguments. Then when I apply "evaluate in place" to the lhs of the action that is supposed to occur when test1 is true, in fact the value of Insert[listA,newEntry,1] is correct, but the rhs gives only the initial value of listA and not the modified value that is on the rhs. Concretely, suppose that in the function argument listA is {121} and newEntry is 200. Then after evaluation of the function (input to the kernel), that line reads, according to "evaluate in place": true, {121} = {200, 121} So it seems that only part of the correct action was taken: 200 was put at the start of listA. But the assignment of this value -- the extended list -- to be the new value of listA did not take place. I then tried using a new name for the modified list, substituting this program line for test1: test1, newListA = Insert[listA, newEntry, 1] What I get here, applying "evaluate in place" after evaluating the function with concrete values as above is: true, newListA = {200, 121} Trace doesn't help because all I get back is the function name with its concrete arguments. Any thoughts? Thank you, Tom

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