works fairly quickly (<10secs) in

Maple 2019
Maple 2018

but fails, or at least takes too long (>1min) for my patience in

Maple 2017
Maple 2016
Maple 2015
Maple 18

By the way responders on this site are Maple users, not (generally-speaking) Maple employees

I have previously noted that *sometimes* the fourier() command "fails", but performing the integration explicitly "works"

This shouldn't really be the case, because (according to the help page), if the command fourier() cannot find the transform in its look-up table, then explict integration is attempted (unless the user sets the NO_INT option)

Even setting 'infolevel' quite high it is not obvious (to me at least) that the fourier() command is even trying explicit integration.

In the attached, explicit integration workss for the erf() function

Download erfFour.mw

using the big green up-arrow in the Mapleprimes toolbar

@Hajra Zeb 

the matrix for any value of 'tau' ( eg 2) just by performing

eval(A, tau=2)

@asma khan 

eval(X, [seq( x[j]=-1+j/3, j=0..N)]);

to my previous worksheet

@radaar 

in the Mapleprimes toolbar, post the "offending" worksheet and specify the Maple version you are using.

@radaar 

depends on the arguments - if these are completely general, then probably(?) not. If these have domains restricted in some way, then possibly(?)

@radaar 

Well, what kind of speedups might be available depend very much on the nature of the arguments which you are supplying to the pochhammer() function.

In the test case you supply, both of these are positive integers. If this is generally true, then use of the pochhammer() function is overkill. There are far more efficient ways to get the same answer.

Such methods *may* be applicable in other cases depending on the domains of the arguments.

Consider the attached, which provides a ~100X speed-up for your test case,  using neither evalf() nor evalhf()

Download evPoch2.mw

@guru kido 

You have used the option metric=arbitrary in the Setup() command.

Neither your original post, nor my earlier response, used this option

@reza gugheri 

which input style you are using: this will be either

1. 'Maple Input', or
2. '2D Input'

Then from the menus, choose Format->Styles: select the appropriate 'style' from the resulting pop-up, then modify it to anything you want (including color)

I have just run this problem through the last few Maple versions

Maple 18:-     No error generated, but no answer
Maple 2015:- No error generated, but no answer
Maple 2016:- No error generated, but no answer
Maple 2017:- No error generated, provides an answer
Maple 2018:- No error generated, provides an answer
Maple 2019:- No error generated, provides an answer

So which version of Maple are you running???

Post a worksheet (big green up-arrow in the Mapleprimes toolbar) which illustrates your problem
 

@acer 

and I may(?) want to withdraw my earlier post, but there is still something odd going on in the attached. Why is the first result different form the others?????

Download confused.mw

The code

restart;
with(VectorCalculus):
assume(x, 'real');
assume(y, 'real');
D[1]((x, y) ->x^2-y^2);

Produces

(x,y)->2 x in Maple 18
(x,y)->2 x in Maple 2015.2
(x,y)->0    in Maple 2016.0
(x,y)->0    in Maple 2017
(x,y)->0    in Maple 2018
(x,y)->0    in Maple 2019

The code

restart;
with(VectorCalculus):
# assume(x, 'real');
# assume(y, 'real');
D[1]((x, y) ->x^2-y^2);

produces

(x,y)->0    in Maple 2019

The code

restart;
#with(VectorCalculus):
assume(x, 'real');
assume(y, 'real');
D[1]((x, y) ->x^2-y^2);

produces

(x,y)->2 x in Maple 2019

So there is definitely something very very odd going on here

@mmcdara 

for

1. Still a pretty basic solution
2. Evaluating dsolve() once - I should have done this before
3. Explanation of parameter passing

(and the output still won't appear on this site!)

Download dsolExpl2.mw