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raj051076 · Beginner Joined: 05 Dec 2002 Posts: 64 Topics: 21

I was just wondering what wil be the equivalent of SUBSTRING in assembler. My requirement is I want to compare a part of a string with something. How do I do this with assembler.

I just started learning assembler and found that it is lot different from other languages.
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Rajib

kolusu · Posted: Tue Dec 10, 2002 11:22 pm Post subject:

raj051076,

Substring Notation

Hope this helps...

cheers

kolusu

raj051076 · Beginner Joined: 05 Dec 2002 Posts: 64 Topics: 21

thanks kolusu....i will try this
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Rajib

RonB · Posted: Wed Dec 11, 2002 9:42 am Post subject:

The reference that Kolusu points out is not used in direct assembly code. As the reference points out, "The substring notation can be used only in conditional assembly instructions." ( i.e. in assembler macros ). In direct code, substring notation is accomplished by coding the correct offset and length into the instruction itself, e.g.

Bill Dennis · Posted: Wed Dec 11, 2002 10:44 am Post subject:

Because Assembler offsets are relative to zero, the comparison should really look like this:
Code:

RonB · Posted: Wed Dec 11, 2002 12:30 pm Post subject:

Right you are Bill. Thanks for the correction.

Ron

nxn00 · Posted: Wed Dec 11, 2002 5:51 pm Post subject:

Rajib,

Could you please post the COBOL statement that you want to convert? Also the Working Storage definition of the fields being used.

If we see that, we can probably give you the BAL instruction to do the same thing.
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Natalie

Bill Dennis · Posted: Thu Dec 12, 2002 10:18 am Post subject:

8) Another fun thing is using the EXecuted form of the instruction so you can vary the length of the compare by setting a value in a register.

Click on this link to read about the EXecute instruction.

Bill

DaveyC · Posted: Thu Dec 12, 2002 10:37 am Post subject:

Bills right, EX is the way to go for variable length strings.

A simple assembler program to convert character digits to a binary integer. The program is naturally re-entrant and expects a control block style work area to be passed.

RonB · Posted: Thu Dec 12, 2002 11:08 am Post subject:

Execute IS the way to go, but if you are not using fixed base+displacements for the source/target fields, it requires that you set registers to the actual addresses of the source/target base+displacement values before invoking the EXecute instruction. That's why I didn't mention it in my first post.

Ron

DaveyC · Posted: Thu Dec 12, 2002 11:36 am Post subject:

RonB,

Of course you're quite right. For fixed length buffers using EXecute is an inefficiency.
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Dave Crayford

RonB · Posted: Thu Dec 12, 2002 4:04 pm Post subject:

While efficiency is not unimportant, readability and maintainability are more important ( in application code, that is - "blackbox" code that may be executed millions of times per run is quite another story ).
My rule-of-thumb is: if the LENGTH of the move/compare is VARIABLE ( i.e. determined at EXECUTION time), I use EXecutes; if the LENGTH of the move/compare is FIXED ( i.e. known at ASSEMBLY time ), I use direct code. Direct code is probably "clearer" to the reader, since it's "in-line", but EXecutes shouldn't be a foreign construct to an able programmer.

Ron

Mervyn · Posted: Thu Dec 12, 2002 6:04 pm Post subject:

Dave, you must be psychic! I identified a need for just that subroutine this afternoon! Thanks a bunch.

By the way, why do you use *-* in the length for the Pack? I would have used zero, but I have to admit that *-* is a good eyecatcher.

Cheers,
Merv

DaveyC · Posted: Fri Dec 13, 2002 2:25 am Post subject:

You are quite right, it's an eyecatcher. I probably copied it from a piece of code that I knocked up feeling a bit slack. Like this:

Mervyn · Posted: Fri Dec 13, 2002 5:01 pm Post subject:

I'm lucky enough to have missed most of it. It's on the telly when I'm either in bed or at work. I'm so thankful our Rugby team beat the three Southern Hemisphere teams in successive weekends.

Your son must be having a great time though?