@goebeld If ex is a mathematical expression, then

indets(ex, specindex(y))

willl return all indexed occurences of y as an independent variable. If you want to find indexed occurences of y as a functional variable (e.g., y[2,2](x)), then use

indets(ex, typefunc(specindex(y)))

or you could search for both of these with the single command

indets(ex, {typefunc, thistype}(specindex(y)));

To return just the set of indices used on y, use

[op]~(subsindets[2](Ys, function, 0, op))

where Ys is the set returned by any of the above indets commands.

There is never a good reason in Maple to convert a mathematical expression to a string to extract mathematical information from it. If you ever feel a need to do it, ask here for help.

@mmcdara My primary purpose was to illustrate that in this case converting it to a module-based package is so trivial that it can be done without even explicitly listing the exports. 

Yes, ToInert is definitely an experts' command, and FromInert is a level even beyond that.

@nm I missed StringTools:-Has in the index. I like it better than my evalb(SearchText("y", str) <> 0). Vote up.

@mmcdara Here, I directly copy the table to the module (record) without explicitly declaring its indices as exports. Nonetheless, a special feature of the Record constructor causes them to become exports anyway. Then I hack the record into a package. This works because a record is a type of module: It has all the module infrastructure except access to the keyword thismodule, which this hack gives it.

restart:
OrthoTable:= copy(orthopoly):
unprotect(orthopoly):
_:= N-> _Inert_ || N:
orthopoly:= (FromInert@subs)(
     ["record"= "package", _(PARAMSEQ)()= _(PARAMSEQ)(_(NAME)("thismodule"))], 
     (ToInert@Record@indices)(OrthoTable, 'pairs')
):
proc(m) uses orthopoly; H(m,x) end proc(2);
                               2    
                            4 x  - 2
with(orthopoly);
                       [G, H, L, P, T, U]

I call this type of hack "surgery": rebuilding with FromInert a modification of a structure exposed with ToInert.

@GFY You need to change all the initial conditions from x=0 to x=8.95. You only changed the first two.

Almost certainly you've unintentionally used gamma= 0.577..., as @mmcdara pointed out. However, my Answer still explains how to get past the singularity.

@mmcdara I believe that it would be trivial to rewrite it as a module. For example,

restart:
OrthoTable:= copy(orthopoly):
unprotect(orthopoly):
orthopoly:= module()
option package;
export 
    G:= eval(OrthoTable[:-G]), 
    H:= eval(OrthoTable[:-H]),
    L:= eval(OrthoTable[:-L]),
    P:= eval(OrthoTable[:-P]),
    T:= eval(OrthoTable[:-T]),
    U:= eval(OrthoTable[:-U])
;    
end module
:
proc(m) uses orthopoly; H(m,x) end proc(2);
                               2    
                            4 x  - 2
use orthopoly in H(2,x) end use;
                               2    
                            4 x  - 2
with(orthopoly);
                       [G, H, L, P, T, U]
H(2,x);
                               2    
                            4 x  - 2

However, for the sake of robustness, and to avoid possible backwards-compatibility issues, I think that it'd be better to name such a quick-and-dirty implementation something other than orthopoly, such as orthomodule.

Just a terminology note: Your equations are not integral equations; they're actually much simpler. Integral equations have unknown functions inside integrals. Your equations have nothing unknown inside the integrals; the only unknowns are the real-valued limits of integration. With a little bit of finesse and floating-point-error control, they should be solvable with fsolve, if they have solutions. It's my bedtime now, but I'll get back to this later today if someone else hasn't solved it yet.

@Oliver Munk Okay, then I guess that you mean that you set Windows Defender to not react to Maple, not that you turned it off completely while using Maple.

@Oliver Munk If you truly need to disable your anti-virus to stop this "freezing" problem, I don't think that that's acceptable. How about trying another anti-virus?

This isn't related to your Question. It's just a general hint for you:, You've done

pde1:= subs(case1, pde);
pde2:= subs(case1, pde1);

These would be better replaced by the single command

pde2:= eval[recurse](pde, case1);

I've found it useful to have a verifcation constructor &under just like the longstanding type constructor &under.

Download VerifyUnder.mw

Could the kernel be modified so that when (a,b)::v is used in a boolean context, verify(a,b,v) would be invoked?

@Oliver Munk To check or set your Autosave status, go to Tools ==> Options from the main menu.

To load a Backup file, go to Files ==> Restore Backup.

@Exiu The best first step towards understanding a Maple data structure is to look at it with lprint, and this is often all that's needed to understand it.

lprint(f);
Sum((1/2-1/2*_alpha)/(x-_alpha),_alpha = RootOf(_Z^2+1))+Sum(1/4*_alpha/(x-
_alpha),_alpha = RootOf(_Z^2+2))

From this we see that Sum is a function (in the Maple sense), the 2nd argument of each function contains the RootOf, and the 1st argument contains the expression whose numertaor and denominator you want..

`&<`:= curry:
[op&<[2,2], [numer, denom] @ op&<1]~(indets(f, specfunc(Sum)));
 {[RootOf(_Z^2+1), [-1+_alpha, -2*x+2*_alpha]], [RootOf(_Z^2+2), [-_alpha, -4*x+4*_alpha]]}

The command allvalues can be used to make RootOfs explicit, when it's possible to do that. Thus allvalues(f) returns the same thing as @vv 's convert(f, radical).
 

@mmcdara I don't know if this is true in the Maple 2015 that you use, but it has been true at least for several years: Unit is exactly the same command as Units:-Unit, regardless of whether the Units package is loaded. This just saves some typing; there's no problem with spelling out Units-Unit if you wish. I can't find documentation for this, but it can be confirmed by

restart:
eval(Unit);
               proc () Units:-Unit(args) end proc

@DJJerome1976 

plots:-polarplot(
    4, thickness= 3, 
    coordinateview= [0..6, 0..2*Pi], axis[2]= [tickmarks= [8, subticks= 2]]
);