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Frequently Asked Questions

How does LSL handle undefined terms?

Larch Frequently Asked Questions
The following answer is adapted from a posting to 'comp.specification.larch' by Horning (July 19, 1995) in response to a question by Leavens (July 18, 1995). The trouble starts with your question: there are no "undefined terms" in LSL. LSL is a language of total functions. There are no partial functions associated with operators, although there may be underspecified operators (i.e., operators bound to functions with different values in different models).

Why does the build fails with undefined symbols?

LessTif Frequently Asked Questions
On the other hand, please make sure that you've built the entire distribution with the same configuration. Not clear ? After running the "configure" command with its options, you should ideally run "make clean". Otherwise e.g. clients/Motif-1.2/mwm/Makefile may be configured such that it looks for stuff that isn't there in lib/Xm/* .

Where can I get a checker for LSL?

Larch Frequently Asked Questions
You can get the MIT releases of the LSL checker using the world-wide web, starting at the following URL. http://www.sds.lcs.mit.edu/spd/larch/lsl.html You can also get the MIT release by anonymous ftp from the following URL. ftp://ftp.sds.lcs.mit.edu/pub/Larch/LSL/ Iowa State, the Larch/C++ group has made available later beta releases of the LSL checker that fix problems with its profligate use of space. You can get the sources for Unix and Windows 95 executables from the following URL.

How should a PHA handle long term debt in terms of writing it off?

Financial Assessment of Public Housing Agencies - FAQs - HUD
Accounting treatment of HUD Guaranteed and Direct Debt" are discussed in "GAAP Flyer #4". HUD guaranteed or direct debt gets written off to Contributed Capital (FDS Line Item No. 503).

What is the difference between LSL and a Larch BISL?

Larch Frequently Asked Questions
The main difference between LSL and a Larch BISL is that in LSL one specifies mathematical theories of the operators that are used in the pre- and postcondition specifications of a Larch BISL. Thus LSL is used to specify mathematical models and auxiliary functions, and the a Larch BISL is used to specify program modules that are to be implemented in some particular programming language.

What is the Larch Shared Language (LSL)?

Larch Frequently Asked Questions
The Larch Shared Language (LSL) (see [Guttag-Horning93], Chapter 4, and [Guttag-Horning-Modet90]) is a language for specifying mathematical theories. LSL is a kind of equational algebraic specification language [Guttag75] [Guttag-Horning78] [Goguen-Thatcher-Wagner78] [Ehrig-Mahr85] [Futatsugi-etal85] [Mosses96] [Loeckx-Ehrich-Wolf96]. That is, specifications in LSL mainly consist of first-order equations between terms.

Where can I find information on-line about LSL?

Larch Frequently Asked Questions
Besides this FAQ, the best place to look is probably your own computer system. You should have a manual page for the LSL checker, if it's installed on your system. Try the Unix command man lsl to see it. You should also look for a directory (such as '/usr/larch/LSL') where the installation of LSL is found. In that directory, you will find a subdirectory 'Doc', where there is some documentation on the checker. See section 2.

What are the sections of an LSL trait?

Larch Frequently Asked Questions
The sections of an LSL trait are determined by the LSL grammar [Guttag-Horning-Modet90]. (See section 2.3 Where can I get a checker for LSL?, for a more recent grammar, which is found in the file 'Doc/lsl3_1.y', for version 3.1, and 'Doc/lsl3_2.y', for version 3.2.

What is the meaning of an LSL specification?

Larch Frequently Asked Questions
LSL trait denotes a theory, which is a collection of true formulas (of sort Bool). This theory contains "the trait's assertions, the conventional axioms of first-order logic, everything that follows from them, and nothing else" (see [Guttag-Horning93], p. 37). For a brief introduction to these ideas, see Chapter 2 of [Guttag-Horning93]; for general background on equational logic, see [Ehrig-Mahr85] or [Loeckx-Ehrich-Wolf96].

Can I specify a partial function in LSL?

Larch Frequently Asked Questions
Technically, no; all functions specified in LSL are total (see section 2.14 What is the meaning of an LSL specification?). Thus every operator specified in LSL takes on some value for every combination of arguments. What you can do is to underspecify such an operator, by not specifying what its value is on all arguments. For example, the operator head in the handbook trait List (see [Guttag-Horning93], p. 173) is underspecified in this sense, because no value is specified for head(empty).

Do I have to specify everything completely in LSL?

Larch Frequently Asked Questions
No, you don't have to specify everything completely in LSL. It's a good idea, in fact, to only specify the aspects that are important for what you are doing. For example, if you want to reason about graph data structures, it's best to not (at first, anyway) try to specify the theory of graphs in great detail. Put in what you want, and go with that. (This won't hurt anything, because whatever you need to prove you'll be forced to add eventually.

What pitfalls are there for LSL specifiers?

Larch Frequently Asked Questions
According to Guaspari (posting to the larch-interest mailing list, on March 8, 1995), "the commonest 'purely mathematical' mistakes" in trait definitions occur when one uses structural induction "over constructors that don't freely generate a sort". To understand this, consider his example, which includes the handbook trait Set (see [Guttag-Horning93], page 167).

Can you give me some tips for specifying things with LSL?

Larch Frequently Asked Questions
The first tip helps you write down an algebraic specification of a sort that is intended to be used as an abstract data type (see [Guttag-Horning78], Section 3.4, and [Guttag-Horning93], Section 4.9). The idea is to divide the set of operators of your sort into generators and observers. A constructor returns your sort, while an observer takes your sort in at least one argument and returns some more primitive sort (such as Bool). The tip (quoted from [Guttag-Horning93], p.

Where can I find handbooks of LSL traits?

Larch Frequently Asked Questions
The most commonly-used handbook of LSL traits is Guttag and Horning's handbook ([Guttag-Horning93], Appendix A). This can be obtained by anonymous ftp with the LSL checker (see section 2.3 Where can I get a checker for LSL?). A hypertext version is on-line in http://www.research.digital.com/SRC/larch/toc.html A general resource for all known handbooks that are publically available is found on the world-wide web, at the following URL. http://www.cs.iastate.edu/~leavens/Handbooks.

Where can I find LaTeX or TeX macros for LSL?

Larch Frequently Asked Questions
You can get a LaTeX style file, 'larch.sty', and a macro file defining a bunch of mathematical symbols, 'larchmath.tex', by anonymous ftp from the following URL. ftp://ftp.cs.iastate.edu/pub/larch/tex The documentation for 'larch.sty' says that it is to be used with LaTeX 2.09. However, it can be used with LaTeX2e. To do so, put the following lines at the start of your LaTeX input.

Why does HitLens report undefined pages?

Web CEO: Frequently Asked Questions
If the page on your Web server is tracked by HitLens, but there is no page name that corresponds to it in the HitLens Tracking system, you will see an 'Undefined page' in the HitLens reports. You inserted the HitLens script into a few local pages using the HitLens wizard and uploaded them to your host. After this, you removed the HitLens code from these pages and pressed 'Apply' or saved changes on exit.

Why does Timezone show as undefined when I schedule an appointment?

The default timezone has not been specified on the Application Settings page, update that field and try again.

Why does my referrer link come up as undefined?

A - You need to edit your options and set 'List Top' to a bigger number. Set it to the number of top referrers you want to show on your site. Then recalculate your stats and everything should be fine.

How does PAPI handle threads?

Frequently Asked Questions
Currently, PAPI only supports thread level measurements with kernel or bound threads. Each thread must manipulate and read its own counters. When a thread is created, it inherits no PAPI information from the calling thread. Support for this kind of functionality is being implemented.

How does the Handle System compare to LDAP?

HANDLE.NET FAQs
the infrastructure level, the Handle System allows individual namespaces to be registered and later discovered by any application over the Internet. Namespaces registered under the Handle System are unique, and queries will always be directed to the responsible handle server for resolution. An LDAP server typically runs in isolation, with service referrals from one namespace to another performed at the peer level when available.
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