tpehrson@javelin.sim.es.com (Tim Clinkenpeel) (06/21/91)
i would like a function to pass back two variables. is this possible? below is an example of what i'd like to accomplish: cx,cy :=checkvalid(cx+offset,cy+offset); -- /=============================/ "1:1 And, yea, Jesus was not quite dead and did / tpehrson@javelin.sim.es.com / commeth down with a wailing and a gnashing of /=====aka: tim clinkenpeel====/ teeth" _The_Bible_][:_Jesus_Strikes_Back_ / [DISCLAIMER: i take prozac] / WARNING: my messages are offensive to morons
smith@ctron.com (Larry Smith) (06/21/91)
In article <1991Jun21.144356.19598@javelin.sim.es.com> tpehrson@javelin.sim.es.com writes: >i would like a function to pass back two variables. is this possible? >below is an example of what i'd like to accomplish: > >cx,cy :=checkvalid(cx+offset,cy+offset); In a word: no. Some Pascals let you return a record, you could try: TYPE RtnVal = RECORD cx, cy: WHATEVER; END; FUNCTION checkvalid(x,y: WHATEVER) : RtnVal; VAR r: RtnVal; BEGIN r := checkvalid(x,y); END. Of course, some Pascals don't. In which case you will need: FUNCTION checkvalid(x,y: WHATEVER): ^RtnVal; and VAR r: ^RtnVal; Not elegant, but it works. -- Larry Smith smith@ctron.com The usual disclaimer stuff...
elmo@troi.cc.rochester.edu (Eric Cabot) (06/22/91)
In <1991Jun21.144356.19598@javelin.sim.es.com> tpehrson@javelin.sim.es.com (Tim Clinkenpeel) writes: >i would like a function to pass back two variables. is this possible? >below is an example of what i'd like to accomplish: >cx,cy :=checkvalid(cx+offset,cy+offset); Well one approach would be to combine the two variables as one and then separate them after the function returns. For example if cx and cy are bytes then you could have cxcy defined as a word and just use Hi(cxcy) and Lo(cyxy) to get them. If cx and cy are words (or integers) then you could put them together as a longint and break that up. I hope this helps. -EC -- =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+= Eric Cabot | elmo@uhura.cc.rochester.edu "insert your face here" | elmo@uordbv.bitnet =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=
dmurdoch@watstat.waterloo.edu (Duncan Murdoch) (06/22/91)
In article <1991Jun21.144356.19598@javelin.sim.es.com> tpehrson@javelin.sim.es.com writes: >i would like a function to pass back two variables. is this possible? >below is an example of what i'd like to accomplish: > >cx,cy :=checkvalid(cx+offset,cy+offset); Not in Turbo or Standard Pascal. The easiest way to do it is to add variables to receive the results as var parameters, which your function (or it could be a procedure) can modify. You have to be a little careful of aliasing, e.g. a declaration procedure checkvalid(var in1,in2:integer;var out1,out2:integer); would likely get messed up on the call checkvalid(cx,cy,cx,cy); since in1 and out1 would both refer to cx, and in2 and out2 would both refer to cy. Passing the input parameters by value (not using var) should work. Duncan Murdoch
gaertner@tertius.in-berlin.de (06/25/91)
In article <1991Jun21.175817.339@maytag.waterloo.edu>, dmurdoch@watstat.waterloo.edu (Duncan Murdoch) writes: > In article <1991Jun21.144356.19598@javelin.sim.es.com> tpehrson@javelin.sim.es.com writes: >>i would like a function to pass back two variables. is this possible? >>below is an example of what i'd like to accomplish: >> >>cx,cy :=checkvalid(cx+offset,cy+offset); > > Not in Turbo or Standard Pascal. The easiest way to do it is to add variables > to receive the results as var parameters, which your function (or it could > be a procedure) can modify. You have to be a little careful of aliasing, > e.g. a declaration > > procedure checkvalid(var in1,in2:integer;var out1,out2:integer); > > would likely get messed up on the call > > checkvalid(cx,cy,cx,cy); > > since in1 and out1 would both refer to cx, and in2 and out2 would both refer to > cy. Passing the input parameters by value (not using var) should work. > > Duncan Murdoch A clearer solution would be PROCEDURE checkvalid ( offset1, offset2 : INTEGER ; { pure input } VAR inout1, inout2 : INTEGER { input/output} ) ; with the call checkvalid ( offset1, offset2, cx, cy ) ; Refering to the original question: Pascal exspects a variable on the left side of an assigment, so there will never be a construct like x,y := expression ; In Algol 60 (and I think in C) it is possible to have a list of variables on the left side of an expression, but note that these variables would get the same value and not different values. Ralf -- Ralf Gaertner gaertner@venus.rz-berlin.mpg.de FHI Berlin
defaria@hpcupt3.cup.hp.com (Andy DeFaria) (06/25/91)
>/ hpcupt3:comp.lang.pascal / tpehrson@javelin.sim.es.com (Tim Clinkenpeel) / 7:43 am Jun 21, 1991 / >i would like a function to pass back two variables. is this possible? >below is an example of what i'd like to accomplish: > >cx,cy :=checkvalid(cx+offset,cy+offset); I'll take a stab here. Assuming that the function name checkvalid is to indeed check if something is valid then why not: function checkvalid (var parm1 : integer; var parm2 : integer) : boolean; Then you could: if not checkvalid (foo, bar) then begin writeln ('Error has occured'); halt end; else { Other processing } This allows you to return a result specifying whether things are OK as well as modify the parameters. Ah I see where your probably having problems! You trying to pass an expression and the compiler doesn't allow var parameters to be expressions - it want a bonified variable that it can modify. You'll need to: var cx : integer; cy : integer; cxnew : integer; cynew : integer; begin ... cxnew := cx + offset; cynew := cy + offset; if checkvalid (cxnew, cynew) then { process } else writeln ('Error');
Russell_Mennie@resbbs.UUCP (Russell Mennie) (06/26/91)
Your other option... would be to use pointers. and have the first pointer
var
p :Pointer;
r :Byte;
point to the byte variable...cslaurie@cybaswan.UUCP (Laurie Moseley ) (06/28/91)
--------------------------------------------------------------------------- If you want to return 2 variables from a function (or 42 for that matter) the easy way to do it is to return a pointer to a linked list of the input data items. That pointer can then be passed to the block which does the processing, and it can process as many as you wish. It even handles null input rather elegantly. I don't know who the original poster was, but if they would like a copy of a program which does this, email me. Laurie (apologies to the referee- original article number not known) ========================================================================== Laurie Moseley Computer Science, University College, Swansea SA2 8PP, UK Tel: +44 792 295399 JANET: cslaurie@uk.ac.swan.pyr ========================================================================= "Why does the Turing test set such abysmally low standards ?" ===========================================================================
hhallika@zeus.calpoly.edu (Harold Hallikainen) (06/29/91)
Ideally, I'd hope we could have a function result type be an array, allowing you to return any specified number of results. I believe you can do this if you want to mess with things a bit. Since a string is the same as a character or byte array, and we are allowed to return strings, declare the function result type as a string. If an array of bytes is a useful result, you can refer to the results directly. If you want some other type of results (maybe even real), seems like something with variant records could be done. Describe the result as a character array and as an array of reals, then refer to the real names. I haven't tried this, but it seems logical (which is probably dangerous!). Good luck! Harold -- Harold Hallikainen ap621@Cleveland.Freenet.edu Hallikainen & Friends, Inc. hhallika@pan.calpoly.edu 141 Suburban Road, Bldg E4 phone 805 541 0200 fax 544 6715 San Luis Obispo, CA 93401-7590 telex 4932775 HFI UI