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Questions tagged [gap-system]

GAP (Groups, Algorithms and Programming) is an open source mathematical software system for discrete computational algebra (https://www.gap-system.org). Ask here non-mathematical questions about programming in GAP; for mathematical questions use the (gap) tag at Mathematics Q&A site: https://math.stackexchange.com/questions/tagged/gap. Other places to ask about GAP are the GAP Forum and GAP Support: https://www.gap-system.org/Contacts/Forum/forum.html

This is the tag for questions related to the computational algebra system GAP.

GAP (Groups, Algorithms and Programming) is a system for computational discrete algebra, with particular emphasis on Computational Group Theory. It provides a programming language, a library of thousands of functions implementing algebraic algorithms written in the GAP language as well as large data libraries of algebraic objects. GAP is used in research and teaching for studying groups and their representations, rings, vector spaces, algebras, combinatorial structures, and more.

If you want to ask a question in this category, please note that there are well-established support channels for GAP users such as GAP Forum and GAP Support which may be more suitable places for such questions with a different (though possibly intersecting) audience, and with a different response rate (which may be faster or slower, dependently on your question). While there may be GAP users and some authors of GAP and/or its packages among the users of this Q&A site, please do not assume that the question on GAP asked here will necessarily be noticed by them.

It may also happen that your question is already answered in the Frequently Asked Questions section of the GAP website or in the GAP Forum (to search GAP Forum archives, click here), or under the "gap" tag on the Mathematics Q&A website.

Finally, if you think that you have discovered a bug in the GAP system, the recommended way to report it is to use the GAP issue tracker on GitHub. Many packages have their own issue trackers, which you can find following the links here.

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Loading GAP packages in Sagemath Cloud

I'm trying to load some GAP packages in a Sagemath Cloud terminal session without sucesss. For example, when I try to load the SCSCP package I get the following error: sage: gap.load_package( "SCSCP"…
user997225
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How to export in GAP

I'm fairly new to programming in GAP which is designed for computational algebra. I have made a computation and wish to make a scatter plot with my results however GAP does not have this functionality. Is it possible/how/where could I find out if…
Celal Bey
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Using functions in GAP in C programs

The programming language GAP has a way of compiling into C code using the compiler GAC. I am trying to test this in the following way, to create a C program from functions written in GAP: first.g PrintEO := function() Print("Hello World");…
rwolst
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How to load my program in GAP system?

After downloading the Windows version of the GAP system, I want to ask if GAP can read the file in specified path in Windows? What is the command to load a GAP script in the Windows environment?
ControlPoly
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A problem with IrreducibleRepresentationsDixon in Julia

I have a question on using GAP in Julia in Jupyter notebook. I am trying to run the following sequence in Julia: using GAP const g =GAP.Globals G = g.SmallGroup(4,2) R = g.IrreducibleRepresentationsDixon(G:unitary) and every time I am obtaining…
Igor Sikora
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Cannot install gappy on a MacBook with M1 Pro chip

I tried to install gappy package for Python using Anaconda, following the instructions given here: https://pypi.org/project/gappy-system/. However, every time after using pip install gappy-system I got the following output: (gap)…
Igor Sikora
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Identify the space group isomorphism between the the group created by AffineCrystGroup and the one given by cryst package

I use the following code snippet to create the diamond space group in GAP with the help of cryst package: gap> M1:=[[0, 0, 1, 0],[1, 0, 0, 0],[0, -1, 0, 0],[1/4, 1/4, 1/4, 1]];; gap> M2:=[[0,0,-1,0],[0,-1,0,0],[1,0,0,0],[0,0,0,1]];; gap>…
Hongyi Zhao
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The set of atomic irrational numbers used to express the character table and corresponding (unitary) representations

I want to calculate the irrational number, expressed by the following formula in gap: 3^(1/7). I've read through the related description here, but still can't figure out the trick. Will numbers like this appear in the computation of the character…
Hongyi Zhao
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Long code line continuation method in GAP language

Take the following code snippet as an example: f:= FreeGroup("P","Q","R","S"); AssignGeneratorVariables(f); g:= f/ParseRelators(f, "P^12=Q^4=R^4=S^8=1, Q^2=R^2, S^2 = P^6*Q^2*R, Q*P=P^7*Q^2*R, Q*P^3=P^3*Q, R*P=P^10*Q*R, R*Q=P^6*Q^3*R,…
Hongyi Zhao
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How to expand {} from xargs in process substitution?

I try to use gap version 4.10 with xargs as following: $ echo 1 | xargs -I '{}' gap -b <( echo 'Display("{}");' ) <( echo 'QUIT;') which returns {} However, it should be 1 Following works $ gap -b <( echo 'Display("123");' ) <( echo…
Hotschke
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How do you see the full "called from" chain of function calls after an error?

Upon getting an error in the GAP command line interpreter, the chain of function calls that led to the error get's truncated, so I can see the start of the chain, which is the function I'd need to fix. gap> MyAwesomeFunction(x,y); Error, resulting…
Mike Pierce
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Is there a way to "catch" errors in GAP?

Suppose I'm using a package function f that takes a single argument x and performs some error checking on that argument. Like, is x of the right type? Etc. And if there is an error then f(x) throws an error with Error(). Is there an easy way to…
Mike Pierce
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What are the function-call/procedure-call pairs in GAP?

By function-call/procedure-call pairs, I mean pairs of functions that do the same thing, except one returns it's result whereas the other alters it's argument(s) to be the result. For example the pair List/Apply. List(list, func) Returns the list…
Mike Pierce
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How do you write a procedure call in GAP?

GAP differentiates a procedure call from a function: functions return a value whereas procedure calls produce an effect. Writing a function is fine, but what's the syntax for writing a procedure call in GAP?
Mike Pierce
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Efficient method of finding all maximum cliques of a graph in GAP

I wish to find all maximum cliques of special types of Cayley graphs called derangement graphs. I work in GAP and I currently use the GRAPE package to establish the following: #This is a nice example to work with. grp := PrimitiveGroup(8,2); n :=…
Dan P.
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