Stems as associative memory (Was: Multi-dimensional arrays in REXX)
One sort of applying this technique of stems is to use the as associative memory - where the content of a storage location is used as an address. Ther rules for resolving elements of a stem variable state that all parts after the first part of a stem are subject to be resolved. As shown in ISDA (the small interactive disassembler in cbttape), which is completely written in Rexx, it works as folllows: Consider a hexcode sequence containing the following (hex)-characters: 0E1A this is resolved to: MVCL R1,R10 Internally it is accomplished by looking for the symbolic representation of x'0E' : OPCODE.0E.FORMAT = 'RR' ; OPCODE.0E.MNEMO = 'MVCL' the Rexx-instructions are: Inst_Form = getInstruction_Format(hexaopcod) . . . getInstruction_Format: arg hxo /* hexadecimal Opcode */ oform = opcode.hxo.fomat return oform /*returns 'RR'*/ . . . IMnemo = opcode.hxo.mnemo /* IMenmo = 'MVCL' */ -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Thu, 19 Mar 2009 01:11:23 -0400, Gerhard Postpischil wrote: Ian S. Worthington wrote: I'm aware of the distinction, but have always felt that that's a fairly reasonable working definition of default, at least up until a reassignment. I suspect that he considers the language assignment of the upper-cased variable name to be the default, hence the distinction? While that's true, it's the lesser concern. Misusing default to describe the universal assignment can mislead the reader to believe that the construct merely defines a value to be used for members otherwise undefined. With this assumption, readers of the following program: /* Rexx */ signal on novalue; /* Universal assignment is not a default value. */ trace R X.42 = 'specific ' say symbol( 'X.42' ) value( 'X.42' ) X.42 = 'universal' say symbol( 'X.42' ) value( 'X.42' ) drop X.42 say symbol( 'X.42' ) value( 'X.42' ) ... may expect incorrect results from the second and/or third say instructions. This is more likely for readers with some programming experience, who are likely to make incorrect and oversimplified assumptions about the implementation mechanism. Even IBM developers have fallen victim: at one point an attempt to optimize storage management caused Rexx to give incorrect results for the third say instruction. This appears to have been repaired by APAR. --gil -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Paul -- What you say, viz: Misusing default to describe the universal assignment can mislead the reader to believe that the construct merely defines a value to be used for members otherwise undefined. is absolutely true, but I would hazard a guess, based on my own 20+ years of rexx experience, that the vast majority of programmers only use, if they use at it at all, the construction x. = 'something' at the top of their programs, and then never change it. Is calling that a default strictly accurate? Of course not. But in the context of the original discussion, does rexx support multi-dimensional arrays? I think that to describe it otherwise in a list of additional features which might be of interest to a newcomer would be a severe case of TMI. BTW, Unless I've misunderstood your point, I'm not sure that your sample program demonstrates the language feature we're discussing. (x. = 'universal' perhaps?) i -- Original Message -- Received: Thu, 19 Mar 2009 06:55:22 AM COT From: Paul Gilmartin paulgboul...@aim.com To: IBM-MAIN@bama.ua.edu Subject: Re: Multi-dimensional arrays in REXX On Thu, 19 Mar 2009 01:11:23 -0400, Gerhard Postpischil wrote: Ian S. Worthington wrote: I'm aware of the distinction, but have always felt that that's a fairly reasonable working definition of default, at least up until a reassignment. I suspect that he considers the language assignment of the upper-cased variable name to be the default, hence the distinction? While that's true, it's the lesser concern. Misusing default to describe the universal assignment can mislead the reader to believe that the construct merely defines a value to be used for members otherwise undefined. With this assumption, readers of the following program: /* Rexx */ signal on novalue; /* Universal assignment is not a default value. */ trace R X.42 = 'specific ' say symbol( 'X.42' ) value( 'X.42' ) X.42 = 'universal' say symbol( 'X.42' ) value( 'X.42' ) drop X.42 say symbol( 'X.42' ) value( 'X.42' ) .. may expect incorrect results from the second and/or third say instructions. This is more likely for readers with some programming experience, who are likely to make incorrect and oversimplified assumptions about the implementation mechanism. Even IBM developers have fallen victim: at one point an attempt to optimize storage management caused Rexx to give incorrect results for the third say instruction. This appears to have been repaired by APAR. --gil -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Stems as associative memory (Was: Multi-dimensional arrays in REXX)
This is a really nice example of the use stems can be put to once one stops thinking of them as arrays. To my mind though it contains one potential bug -- it depends on FORMAT and MNENO remaining uninitialized. I would prefer to prefix such symbols with, eg, a 0 to make sure they couldn't be, eg 0FORMAT and 0MNEMO. Or, in programs with more complex lookups, I would often be more explicit: 0Opcode2Mnemonic and 0Opcode2Format, which helps me to remember what to put in as as well as what (should) come out: useful as my memory fades... i -- Original Message -- Received: Thu, 19 Mar 2009 02:51:09 AM COT From: Arthur Fichtl arthur_fic...@afisumag.de To: IBM-MAIN@bama.ua.edu Subject: Stems as associative memory (Was: Multi-dimensional arrays in REXX) One sort of applying this technique of stems is to use the as associative memory - where the content of a storage location is used as an address. Ther rules for resolving elements of a stem variable state that all parts after the first part of a stem are subject to be resolved. As shown in ISDA (the small interactive disassembler in cbttape), which is completely written in Rexx, it works as folllows: Consider a hexcode sequence containing the following (hex)-characters: 0E1A this is resolved to: MVCL R1,R10 Internally it is accomplished by looking for the symbolic representation of x'0E' : OPCODE.0E.FORMAT = 'RR' ; OPCODE.0E.MNEMO = 'MVCL' the Rexx-instructions are: Inst_Form = getInstruction_Format(hexaopcod) . . . getInstruction_Format: arg hxo /* hexadecimal Opcode */ oform = opcode.hxo.fomat return oform /*returns 'RR'*/ . . . IMnemo = opcode.hxo.mnemo /* IMenmo = 'MVCL' */ -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Thu, 19 Mar 2009 07:37:08 -0500, Ian S. Worthington wrote: Paul -- What you say, viz: Misusing default to describe the universal assignment can mislead the reader to believe that the construct merely defines a value to be used for members otherwise undefined. is absolutely true, but I would hazard a guess, based on my own 20+ years of rexx experience, that the vast majority of programmers only use, if they use at it at all, the construction x. = 'something' at the top of their programs, and then never change it. Is calling that a default strictly accurate? Of course not. But in the context of the original discussion, does rexx support multi-dimensional arrays? I think that to describe it otherwise in a list of additional features which might be of interest to a newcomer would be a severe case of TMI. The infrequency of use of a facility fails to justify the incorrect description. Rather, it aggravates the astonishment factor when the programmer encounters the behavior, perhaps inadvertently. Suppose: X. = 'something' do I = 1 to 10; X.I = 'defined'; end drop X.7 say X.7 The description in the manual is correct; describing it with the less specific term default might lead the programmer to expect the program to say something rather than X.7, or at least to be uncertain. BTW, Unless I've misunderstood your point, I'm not sure that your sample program demonstrates the language feature we're discussing. (x. = 'universal' perhaps?) I stand corrected. Lazy code copying and inadequate testing. (When corrected, the output is the same.) BTW, the APAR I've mentioned is OA17169, closed SUG in 2006, then The fix for this SUG APAR was shipped in the base for z/OS V1R9. (IBM has lately updated FIN and SUG APARs when/if the fix is shipped. Thanks, IBM.) -- gil -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Thu, 19 Mar 2009 09:21:12 -0500, Paul Gilmartin paulgboul...@aim.com wrote: ... The infrequency of use of a facility fails to justify the incorrect description. Rather, it aggravates the astonishment factor when the programmer encounters the behavior, perhaps inadvertently. Suppose: X. = 'something' do I = 1 to 10; X.I = 'defined'; end drop X.7 say X.7 The description in the manual is correct; describing it with the less specific term default might lead the programmer to expect the program to say something rather than X.7, or at least to be uncertain. ... I agree, but I think the astonishment is aimed at the drop rather than the stem assignment. (At least MY astonishment is.) That behavior implies that the interpreter has to maintain both a list of specifically assigned variables and a list of specifically dropped variables (at least for stems that have been assigned). I have no idea how the interpreters actually support the behavior of stem initialization, but I'm quite sure they don't predefine and assign every possible variable for the given stem. They must, in fact, treat the assigned value as a default to be used for each unassigned and undropped variable associated with the stem. Including dropped variables in that behavior just adds work for the interpreter. Collishaw books include a sample of this behavior so there is no doubt he intended the language to work this way, but I am still astonished. Pat O'Keefe -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Thu, Mar 19, 2009 at 3:26 PM, Patrick O'Keefe patrick.oke...@wamu.net wrote: I agree, but I think the astonishment is aimed at the drop rather than the stem assignment. (At least MY astonishment is.) That behavior implies that the interpreter has to maintain both a list of specifically assigned variables and a list of specifically dropped variables (at least for stems that have been assigned). I have no idea how the interpreters actually support the behavior of stem initialization, but I'm quite sure they don't predefine and assign every possible variable for the given stem. They must, in fact, treat the assigned value as a default to be used for each unassigned and undropped variable associated with the stem. Including dropped variables in that behavior just adds work for the interpreter. The key is to understand how the variables are maintained: in a b-tree. So x.='foo' sets a node for x.. Once you explicitly set x.banana, a new leaf is created for that. And when you drop a variable, the leaf is maintained/created too. Admittedly, the implementation isn't obvious, but it does allow for arbitrary tails. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Thu, 19 Mar 2009 14:26:53 -0500, Patrick O'Keefe wrote: The description in the manual is correct; describing it with the less specific term default might lead the programmer to expect the program to say something rather than X.7, or at least to be uncertain. ... I agree, but I think the astonishment is aimed at the drop rather than the stem assignment. (At least MY astonishment is.) That behavior implies that the interpreter has to maintain both a list of specifically assigned variables and a list of specifically dropped variables (at least for stems that have been assigned). I have no idea how the interpreters actually support the behavior of stem initialization, but I'm quite sure they don't predefine and assign every possible variable for the given stem. They must, in fact, treat the assigned value as a default to be used for each unassigned and undropped variable associated with the stem. Including dropped variables in that behavior just adds work for the interpreter. Collishaw books include a sample of this behavior so there is no doubt he intended the language to work this way, but I am still astonished. You have a pretty good description of how the misunderstanding arises: journeyperson programmers attempt to infer an mechanism of implementation, then erroneously assume the developers take shortcuts because it's too complicated to do it right. I confess I often do the same. But then I test. Sometimes I'm plesantly surprised to find the implementation meets the specification. Other times, I find that the implementor took the shortcut, and I submit a PMR. This thoroughly annoys the support people who argue that I should expect that it would be implemented in the simple and obvious way, not as specified. I may not be able to do that much longer. -- gil -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Terry -- Subtle language gotchas, as previously discussed, not withstanding, the practical upshot is that yes, rexx *does* support multidimensional arrays, and sparse ones with default values to boot. It implements them as a conceptual subset of stems, and they are indexed with strings rather than by integers which actually makes them rather more powerful once one breaks out of the array mindset. I've been using them for years without any problems. i -- Original Message -- Received: Tue, 17 Mar 2009 05:10:37 PM COT From: Terry Sambrooks terry.sambro...@btclick.com To: IBM-MAIN@bama.ua.edu Subject: Multi-dimensional arrays in REXX Hi, I have done a search of the archives, and read the relevant REXX manuals and am left with a need for a second opinion on my conclusion. The question I have been asked relates to whether REXX supports multi-dimensional arrays. There is a lot of discussion in the manuals about single dimension arrays a.k.a. STEM variables, but additional dimensions are not covered which leads me to conclude that multi-dimensional arrays are not supported. I know this question is better directed at the REXX New Group, but I feel sure that there is enough expertise available here to confirm my assessment or correct any erroneous view I may have formed. Kind regards - Terry Terry Sambrooks Director KMS-IT Limited 228 Abbeydale Road South Dore, Sheffield, S17 3LA, UK Tel: +44 (0)114 262 0933 WEB: www.legac-e.co.uk Company Reg: 3767263 at the above address All outgoing E-mail is scanned, but it remains the recipient's responsibility to ensure their system is protected from spy-ware, trojans, viruses, and worms. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Larry Terry As stated before REXX STEM's are not arrays. Each element is treated as a string, not a number. So: names.john.sam.bill.1.sally='abc' is legal and accepted. Just like A.1.2.3.4.5=99 is accepted. REXX variables are restricted to storage and if assigned to a number will also be restricted by the DIGITS command. Many people I have talked with do not understand that a STEM in REXX could be non-numeric. They always associated STEM's with arrays, but they are not. The convention is that stem.0 or stem.x.0 contains the number of elements in the STEM, but this is not enforced by REXX. It is just a standard. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Ian S. Worthington wrote: It implements them as a conceptual subset of stems, and they are indexed with strings rather than by integers which actually makes them rather more powerful once one breaks out of the array mindset. All generalities are false (?) I'm not sure what you mean by the array mindset? Do you seriously advocate solving a determinant by defining it as DET.ONE.ONE, DET.ONE.TWO, etc. rather than DET.1.1, etc.? I don't consider this a mindset, but rather a prudent approach (and I realize that the computation in ForTran or PL/I would be faster, but could also be less accurate). Gerhard Postpischil Bradford, VT -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
I refer to the tendency of programmers new to rexx stems, but familiar with hll arrays, to reduce their (non-numerical) problem to one of integral indices into arrays rather than make full use of the rexx stem facility. i -- Original Message -- Received: Wed, 18 Mar 2009 09:29:58 AM COT From: Gerhard Postpischil gerh...@valley.net To: IBM-MAIN@bama.ua.edu Subject: Re: Multi-dimensional arrays in REXX Ian S. Worthington wrote: It implements them as a conceptual subset of stems, and they are indexed with strings rather than by integers which actually makes them rather more powerful once one breaks out of the array mindset. All generalities are false (?) I'm not sure what you mean by the array mindset? Do you seriously advocate solving a determinant by defining it as DET.ONE.ONE, DET.ONE.TWO, etc. rather than DET.1.1, etc.? I don't consider this a mindset, but rather a prudent approach (and I realize that the computation in ForTran or PL/I would be faster, but could also be less accurate). Gerhard Postpischil Bradford, VT -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Ian S. Worthington wrote: I refer to the tendency of programmers new to rexx stems, but familiar with hll arrays, to reduce their (non-numerical) problem to one of integral indices into arrays rather than make full use of the rexx stem facility. I agree completely, but that was not the meaning I got from your original statement. Gerhard Postpischil Bradford, VT -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Regrettably you can only set a default for the stem as a whole, not for a subset of the variable space. Its one of my pet peeves. i -- Original Message -- Received: Wed, 18 Mar 2009 03:08:19 PM COT From: Patrick O'Keefe patrick.oke...@wamu.net To: IBM-MAIN@bama.ua.edu Subject: Re: Multi-dimensional arrays in REXX On Wed, 18 Mar 2009 09:48:10 -0500, Ian S. Worthington ianworthing...@usa.net wrote: It implements them as a conceptual subset of stems, and they are indexed with strings rather than by integers which actually makes them rather more powerful once one breaks out of the array mindset. I'm not sure what you mean by the array mindset? I refer to the tendency of programmers new to rexx stems, but familiar with hll arrays, to reduce their (non-numerical) problem to one of integral indices into arrays rather than make full use of the rexx stem facility. ... I'm not new to REXX stems nor recently familiar with HLL arrays, but *still* make REXX blunders based on array-think. It's seductive. An individual compound variable can be assigned a value, and the stem can be assigned a value. That's all there is with REXX stems. You cannot assign a value to a row or a column (or any other more abstract partitioning of the compound variable space) no matter how much you might want to. I conceptually had a very non-array-like structure BASE.i BASE.key.n Where i and n were integers and key was alphanumeric. I wanted all BASE.key.n to be set to the value of key for a fixed set of keys. But what I wanted doesn't count for much. FOO.BAR. = BAR is invalid. :-( I think my attempted logic came more from wishful thinking than from any knowledge of HLL array processing. Even if more powerful that arrays, there are limits to compund varaible processing in REXX. Pat O'Keefe -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Wed, 18 Mar 2009 15:21:31 -0500, Ian S. Worthington wrote: Regrettably you can only set a default for the stem as a whole, not for a subset of the variable space. It is *not* a default, and Rexx documentation avoids the possibly misleading use of default by a correct description that: X. = 'blank' assigns [in effect] the value 'blank' to every possible member of the compound variable with stem X. Not only freshman and sophomore Rexx programmers fail to understand this, but even IBM developers have caused a violation of the specification by introducing a misconceived optimization. -- gil -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Wed, 18 Mar 2009 09:48:10 -0500, Ian S. Worthington ianworthing...@usa.net wrote: It implements them as a conceptual subset of stems, and they are indexed with strings rather than by integers which actually makes them rather more powerful once one breaks out of the array mindset. I'm not sure what you mean by the array mindset? I refer to the tendency of programmers new to rexx stems, but familiar with hll arrays, to reduce their (non-numerical) problem to one of integral indices into arrays rather than make full use of the rexx stem facility. ... I'm not new to REXX stems nor recently familiar with HLL arrays, but *still* make REXX blunders based on array-think. It's seductive. An individual compound variable can be assigned a value, and the stem can be assigned a value. That's all there is with REXX stems. You cannot assign a value to a row or a column (or any other more abstract partitioning of the compound variable space) no matter how much you might want to. I conceptually had a very non-array-like structure BASE.i BASE.key.n Where i and n were integers and key was alphanumeric. I wanted all BASE.key.n to be set to the value of key for a fixed set of keys. But what I wanted doesn't count for much. FOO.BAR. = BAR is invalid. :-( I think my attempted logic came more from wishful thinking than from any knowledge of HLL array processing. Even if more powerful that arrays, there are limits to compund varaible processing in REXX. Pat O'Keefe -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Hi, I though a quick thank you was in order to all those who responded to my earlier query. Having reviewed the various responses and combined that information with some gleaned from query on STEMs posted earlier in the week by somebody else. I have been able to correct my misunderstanding and produce a demonstration routine. Thanks again - Terry Terry Sambrooks Director KMS-IT Limited 228 Abbeydale Road South Dore, Sheffield, S17 3LA, UK Tel: +44 (0)114 262 0933 WEB: www.legac-e.co.uk Company Reg: 3767263 at the above address All outgoing E-mail is scanned, but it remains the recipient's responsibility to ensure their system is protected from spy-ware, trojans, viruses, and worms. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
I'm aware of the distinction, but have always felt that that's a fairly reasonable working definition of default, at least up until a reassignment. i -- Original Message -- Received: Wed, 18 Mar 2009 03:39:27 PM COT From: Paul Gilmartin paulgboul...@aim.com To: IBM-MAIN@bama.ua.edu Subject: Re: Multi-dimensional arrays in REXX On Wed, 18 Mar 2009 15:21:31 -0500, Ian S. Worthington wrote: Regrettably you can only set a default for the stem as a whole, not for a subset of the variable space. It is *not* a default, and Rexx documentation avoids the possibly misleading use of default by a correct description that: X. = 'blank' assigns [in effect] the value 'blank' to every possible member of the compound variable with stem X. Not only freshman and sophomore Rexx programmers fail to understand this, but even IBM developers have caused a violation of the specification by introducing a misconceived optimization. -- gil -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Wed, 18 Mar 2009 15:36:24 -0500, Paul Gilmartin paulgboul...@aim.com wrote: On Wed, 18 Mar 2009 15:21:31 -0500, Ian S. Worthington wrote: Regrettably you can only set a default for the stem as a whole, not for a subset of the variable space. It is *not* a default, and Rexx documentation avoids the possibly misleading use of default by a correct description that: X. = 'blank' assigns [in effect] the value 'blank' to every possible member of the compound variable with stem X. ... Whether or not this behavior fits the definition of default, it does highlight the meaning of stem. In the compund variable A.B.C.D the stem is A., not A.B. or A.B.C., and only the stem or a whole compound variable can be assigned a value. Last I knew (and admitedly, that was 25 years ago) PL/I was even less flexable than that. You cfould assign a value to a whole dimension of an array, but that generated code to set every element in that dimension to that value. You can obviously do the same thing (explicitly) in REXX but that is a lot different (and a whole lot less efficient) than setting an initial value for otherwise unset elements of a compound variable. It would be tough for REXX to handle initilized stems differently, actually. Pat O'Keefe -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Ian S. Worthington wrote: I'm aware of the distinction, but have always felt that that's a fairly reasonable working definition of default, at least up until a reassignment. I suspect that he considers the language assignment of the upper-cased variable name to be the default, hence the distinction? Gerhard Postpischil Bradford, VT -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Multi-dimensional arrays in REXX
Hi, I have done a search of the archives, and read the relevant REXX manuals and am left with a need for a second opinion on my conclusion. The question I have been asked relates to whether REXX supports multi-dimensional arrays. There is a lot of discussion in the manuals about single dimension arrays a.k.a. STEM variables, but additional dimensions are not covered which leads me to conclude that multi-dimensional arrays are not supported. I know this question is better directed at the REXX New Group, but I feel sure that there is enough expertise available here to confirm my assessment or correct any erroneous view I may have formed. Kind regards - Terry Terry Sambrooks Director KMS-IT Limited 228 Abbeydale Road South Dore, Sheffield, S17 3LA, UK Tel: +44 (0)114 262 0933 WEB: www.legac-e.co.uk Company Reg: 3767263 at the above address All outgoing E-mail is scanned, but it remains the recipient's responsibility to ensure their system is protected from spy-ware, trojans, viruses, and worms. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Tue, 17 Mar 2009 22:09:15 - Terry Sambrooks terry.sambro...@btclick.com wrote: :I have done a search of the archives, and read the relevant REXX manuals and :am left with a need for a second opinion on my conclusion. :The question I have been asked relates to whether REXX supports :multi-dimensional arrays. There is a lot of discussion in the manuals about :single dimension arrays a.k.a. STEM variables, but additional dimensions are :not covered which leads me to conclude that multi-dimensional arrays are not :supported. Why can't stems be multi-dimensional? STEM.x.y.z :I know this question is better directed at the REXX New Group, but I feel :sure that there is enough expertise available here to confirm my assessment :or correct any erroneous view I may have formed. -- Binyamin Dissen bdis...@dissensoftware.com http://www.dissensoftware.com Director, Dissen Software, Bar Grill - Israel Should you use the mailblocks package and expect a response from me, you should preauthorize the dissensoftware.com domain. I very rarely bother responding to challenge/response systems, especially those from irresponsible companies. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Wed, 18 Mar 2009 00:11:35 +0200, Binyamin Dissen wrote: On Tue, 17 Mar 2009 22:09:15 - Terry Sambrooks wrote: :The question I have been asked relates to whether REXX supports :multi-dimensional arrays. There is a lot of discussion in the manuals about :single dimension arrays a.k.a. STEM variables, but additional dimensions are :not covered which leads me to conclude that multi-dimensional arrays are not :supported. True, they are not. Why can't stems be multi-dimensional? STEM.x.y.z Which is equivalent to: I = x'.'y'.'z STEM.I But this suffers an ambiguity. Consider: I = 'A.B' J = 'C' X = 'A' Y = 'B.C' Then STEM.I.J and STEM.X.Y refer to the same variable, even though IX and JY. When this occurs, admittedly seldom but not never, the astonishment factor is likely to be enormous. FORTRAN introduces a similar ambiguity with its flattening of subscripts. -- gil -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
On Tue, 17 Mar 2009 17:22:29 -0500 Paul Gilmartin paulgboul...@aim.com wrote: :On Wed, 18 Mar 2009 00:11:35 +0200, Binyamin Dissen wrote: :On Tue, 17 Mar 2009 22:09:15 - Terry Sambrooks wrote: ::The question I have been asked relates to whether REXX supports ::multi-dimensional arrays. There is a lot of discussion in the manuals about ::single dimension arrays a.k.a. STEM variables, but additional dimensions are ::not covered which leads me to conclude that multi-dimensional arrays are not ::supported. :True, they are not. :Why can't stems be multi-dimensional? :STEM.x.y.z :Which is equivalent to: :I = x'.'y'.'z :STEM.I :But this suffers an ambiguity. Consider: :I = 'A.B' :J = 'C' :X = 'A' :Y = 'B.C' :Then STEM.I.J and STEM.X.Y refer to the same variable, :even though IX and JY. When this occurs, admittedly :seldom but not never, the astonishment factor is likely :to be enormous. Also when a = 4 b = 04 Even though a=b, stem.Astem.B Plenty of ammunition if one plans to shoot at the toes. :FORTRAN introduces a similar ambiguity with its flattening :of subscripts. -- Binyamin Dissen bdis...@dissensoftware.com http://www.dissensoftware.com Director, Dissen Software, Bar Grill - Israel Should you use the mailblocks package and expect a response from me, you should preauthorize the dissensoftware.com domain. I very rarely bother responding to challenge/response systems, especially those from irresponsible companies. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
Re: Multi-dimensional arrays in REXX
Terry, OK - I'm no REXX expert, so take this for what it's worth: In the technical/classical sense of arrays, REXX does not have any support of arrays per se - either single or multi-dimensional. When I was using Fortran you had: Dimension array(10,10) Do I = 1 to 10 Do X = 1 to 10 Array(I,X) = some value End End Instead, Rexx has STEM variables that can be made to work as arrays: Do I = 1 to 10; Stemvar.I = some value; End; This makes STEM variables 'look' like arrays. However, REXX and STEM variables are perfectly happy with saying Stemvar.5 = some value The above only creates the STEM variable 'stemvar.5' and assigns it some value. Note there is no STEM variable of 'stemvar.1/2/3/4/6/7/8/9/10'. Only 'stemvar.5' exists. Also, please save yourself some embarrassment when talking to anyone who is a REXX bigot/user and NEVER - NEVER say that stem variables are arrays. Doing so causes you life-long shame. HTH HITACHI DATA SYSTEMS Raymond E. Noal Senior Technical Engineer Office: (408) 970 - 7978 -Original Message- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Terry Sambrooks Sent: Tuesday, March 17, 2009 3:09 PM To: IBM-MAIN@bama.ua.edu Subject: Multi-dimensional arrays in REXX Hi, I have done a search of the archives, and read the relevant REXX manuals and am left with a need for a second opinion on my conclusion. The question I have been asked relates to whether REXX supports multi-dimensional arrays. There is a lot of discussion in the manuals about single dimension arrays a.k.a. STEM variables, but additional dimensions are not covered which leads me to conclude that multi-dimensional arrays are not supported. I know this question is better directed at the REXX New Group, but I feel sure that there is enough expertise available here to confirm my assessment or correct any erroneous view I may have formed. Kind regards - Terry Terry Sambrooks Director KMS-IT Limited 228 Abbeydale Road South Dore, Sheffield, S17 3LA, UK Tel: +44 (0)114 262 0933 WEB: www.legac-e.co.uk Company Reg: 3767263 at the above address All outgoing E-mail is scanned, but it remains the recipient's responsibility to ensure their system is protected from spy-ware, trojans, viruses, and worms. -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html -- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
