I am looking to return all the substrings of a string that match a particular pattern (regexp). This is a very common text processing operation.

StringTools[RegMatch] returns boolean about whether the given pattern exists somewhere in the string. That's a start, but it is not efficient to hunt around for where the match is in order to extract the characters.

StringTools[Search] and [SearchAll] can return position information, but they work on exact matches of the pattern space, not on regular expressions. I could pre-generate all the possible matching sequences of up to some length and search for those exactly, but that is inconvenient at best and pretty much useless if there is a .* or .+ in the regular expression (as the space of potential matches grows exponentially.)

StringTools[RegSub] can be used to find one match by using something like ".*(REALPATTERN).*" = "\1" but since this does not extract any position information, one would at the very least then have to StringTools[Search] of the exact match to determine the position, then take a substring of the original string, and continue searching. And if you are going to do that, you might as well just use StringTools[RegMatch] with an optional third argument of a symbol to return the matched characters, instead of fooliing around with deleting everything else using RegSub.

Have I overlooked a possibility?

Example of use:

I would like to search "variable %1 needs to be of the form %3+2.9 in order to use routine %2 to find the fizturl", extracting the "%1", "%3", "%2". This would be regular expression "%[0-9]+". Notice that there might be other digits in the string that I do not want to extract, so I cannot just search for digits. I also cannot just remove all characters "[^0-9%]" as that would leave digits and would, for example, merge together the %3+2.9 into %329 leaving post-processing to extract the true pattern matches.

For what I am doing at the moment, I do not need to know the positions those occured at, just the matches.

Why is it that

dismantle(3*a);

returns a SUM entity?

SUM(3)
   NAME(4): a
   INTPOS(2): 3

dismantle(3+a);

also returns a SUM entry

SUM(5)
   NAME(4): a
   INTPOS(2): 1
   INTPOS(2): 3
   INTPOS(2): 1

ToInert() looks fine for both of these.

Tested on Maple 16, Maple 17, Maple 18

I want to solve a Laplace integral transform step-by-step its as follows:

f(t):=e^at

IntTutor(Int(e^-st f(t),t=0..infinity)

but it says that the expression can't be integrated, and secondly it does not work with 'infinity'. How I can solve this for step-by-step solution?

Thanxs

When I open My Maple 18 on my Macbook pro, with all updates on the operating system and on Java, my Maple starts up fine, but when I press 2+2 and the enter, nothing happens.

I have tried reinstalling Maple, without any change of the problem

Per Kirkegaard

hi

i want to use Direct Search Package for solve system of equation but i have an error:

Error, SolveEquations is not a command in the DirectSearch package.

please help me. code is attached.boltmohasebe.mw

Hi all.

I try to get the real part from the complex expression. But it turns out to not be the simplest result:

A:=I*sin(k*Pi*(x-h*cos(theta))/a)*sin(l*Pi*(y-h*sin(theta))/b)*exp(-I*k[0]*h)*sin(k*Pi*x/a)*sin(l*Pi*y/b)

convert(exp(-I*k[0]*h), sin);

simplify(Re(A));

Maple results in:

Re(sin(k*Pi*(-x+h*cos(theta))/a)*sin(l*Pi*(-y+h*sin(theta))/b)*exp(-I*k[0]*h)*sin(k*Pi*x/a)*sin(l*Pi*y/b))

while the simplified result should be:

sin(k*Pi*(x-h*cos(theta))/a)*sin(l*Pi*(y-h*sin(theta))/b)*sin(k*Pi*x/a)*sin(l*Pi*y/b)*sin(k[0]*h)

I wander how to get the simplifyed result in maple. Thanks

How can I breal kong code lines in "Code Edit Region" like "..." in Matlab?

How can one use maple to linearized nonlinear ODE of this type Linearize.mw

with maple.

Best regards.

Hi,

  Suppose I have the following code

***

f[1]:=x1^2+x2;
f[2]:=-x2^3+x1-2;

solve({f[1], f[2]}, {x1, x2}):
a,b:= eval([x1, x2], %[1])[]:
a, b;

***

It could work and give me "1 and -1". 

I would like to have a general subroutine, solving f[1]...f[n]. I cannot input  "solve({f[1], f[2],....,f[n]}, {x1, x2}):" just like that. Is ther any way to use "solve" or similar module to handle arbitary number of variables?

I am trying to use solve to determine 5 unknowns from 12 equations each with seperate data points); however, maple requires you to have equal number equations and variables. Is there any way around this?

There are two ways of expressing the solution to a cubic equation, one of them uses cos and arccos [1]. How do I / is there a way to ask Maple to get this form?

More generally, can Maple be instructucted to solve equations using trig identities?

[1] http://en.wikibooks.org/wiki/Trigonometry/The_solution_of_cubic_equations

I am fitting polynomial differential equations to data, and I came across some troubling behavior. I have sets of coordinates in x, y, z, and values w at these coordinates. The x,y,z coordinates and the data at these coordinates are concatenations of three subsets of data each, and depending on the order of the concatenation, I get different polynomials from the stats fit command. The difference is not trivial -- it makes a huge differentce in the stability of the differential equations. I have written a demonstration worksheet to show this problem.

John Starrett

Solve IVP with complex coef. with compplex varables numerically..

the sys. is x'=-iDelta1x(t)+y(t)+epsilon

y'=-iDelta2y(t)+x(t)z(t)

z'=-2(x*(t)y(t)+x(t)y*(t)), where * means complex conjugate 

I solve it as:

epsilon:=5:Delta1:=4:Delta2:=4:assume(z(t),real):

var:={x_R(t),y_R(t),z_R(t),x_I(t),y_I(t),z_I(t)}:
dsys :={diff(x(t),t)=-I*Delta1*x(t)+y(t)+epsilon, diff(y(t),t)=-I*Delta2*y(t)+x(t)*z(t), diff(z(t),t)=-2*(conjugate(x(t))*y(t)+conjugate(y(t))*x(t))}:
functions := indets(dsys, anyfunc(identical(t))):
redefinitions := map(f -> f = cat(op(0, f), _R)(t) + I*cat(op(0,f), _I)(t), functions):
newsys := map(evalc @ Re, redefinitions) union map(evalc @ Im, redefinitions):

incs := {x_R(0)=0, x_I(0)=0, y_R(0)=0, y_I(0)=0,z_R(0)=-1/2, z_I(0)=0}:
dsol1 :=dsolve({newsys,incs},var,numeric, output=listprocedure, abserr=1e-9, relerr=1e-8,range=0..1):

but it seems there is not runing propebly

If we a complex number in Maple, like for example:

I*b+a+x+I*y+I^2*c

How can we make maple rewrite it like this?

a+x-c+I*(y+b)

I tried using the comands Re(%) and Im(%) but Re just gives the whole expression again and Im gives 0.

Hey

I have a excel spreadsheet with a number of data points which I want to plot in Maple.  I have imported the data and I did manage to produce a point plot, but how can I exclude some of the data points when I plot the point plot?
I would, for example, like to exclude the negative values and only plot the data which is greater than zero.

Thanks