future plans:
-------------
* function investigation: intervals of monotonicity, convexity
    and concavity
* ODE:exact equations.
* vylepsit zobrazeni celeho retezce funkci, pres ktere prochazime u
  transformaci grafu zakl el. fci (u PDF  animace). 
* Definicni obor funkci jedne promenne - upravit na vystup do PDF.
* Definicni obor funkci dvou promennych - upravit na vystup do PDF, vystup 
  do html nechat jako jednu z voleb.
* test, jestli jsou v urcitych integralech meze konstanty (a ne napr."exp")
* use a string variable for the name of the maxima executable and the
  same for formconv executable (this is easier, we call formconv using
  echo and /usr/bin/formconv and hence it is possible to grep in all
  *.php and *.pl files)
* lde2: split rhs like x+exp(x)*sin(x)+exp(x)*cos(x) into two (not
   three) right hand sides
* ode: run maxima parser before proceeding equation (like xy'=exp(x) )
* integral: if function can be splitted into sum and is in x variable,
   we can investigate terms separately. Allow this feature also for
   general variable (by converting into x variable first)


changes from January 2008
-------------------------

Some changes are motivatied by error messages from logs. It may
hapen that the problem which caused an error works well after few 
days. 

march 2009
* domains: ratprint:false   - solves the problem related to domain of
      1/3*log(x**3-1+sqrt(x**6-2*x**3))

february 2009
* integral: handle problem even if the user enters 
      "integral(function,x)" 
* all: computations are refused, if the server load is large
* offline version (VMware)
* domains: Maxima 5.17 is used to parse the expression. Model example 
    is sqrt(x^2+y^2-4) - Maxima 5.13 session failed.
    Thanks to Simona Fisnarova.
* derivatives: no simplifications if %i appears in the reslut. 
   Model  example for the problem is sqrt(1-x^2)+sqrt(x^2-1). 
   Thanks to David Kvapil.

january 2009
* integral: improved messages when doing substitution tan(x/2)=t and
     tan(x)=t
* integral: most TeX strings are generated by Maxima to avoid too many
    calls of formconv (which is still used heavily)
* autsyst: fixed the case with double root of characteristic equation
* integral: fixed broken trigsimp in integral with respect to y (x is
     constant)
* geom. application of integral: added float wrapper for bounds for
     integration using quadpack and fixed gettext call in geom.pl file 
     (there was a problem with integration on the interval like 1..e^3)
* ode: fixed missing brace for equations with integrating factor
* function ivestigations: evaluation of y'' preceedes solving y'=0 
     (and hence y'' is evaluated even if y'=0 fails for some reason)
* integral - geom: test that the lower limit which defines a region in the 
     plane is smaller than uppe limit
* ode: fixed solve command for ODE's. 
     y'=y*log(y) does not have constant solution y=0, but y=0 is one of results  
     of maxima command solve(y*log(y),y)

december 2008
* integral2: improved test that radial variable in polar coordinates is nonegative
* trapeziodal: added float around limits for numerical integration 
    (the limits could be something like %e^2)
* changed behavior related to jacobian in double integral and inititated
    support for internalizations and gettext
* highlighting errors and fixed error messages
* shifting graph - added partfrac to handle functions (ax+b)/(cx+d)

november 2008
* autsyst: parameters allowed only when evaluating stationary points. 
      (we get false error message about zero jacobian)
* autsyts: the type of stationary point is printed out and some
      details to the solution were added
* domains: no complex numbers in the solution of an algebraic equations

october 2008
* trapeziodal: romberg replaced by quad_qags. 
  (Romberg has problem with convergence if integral is exactly zero)
* ode: homogeneous: check that the "constant solution" does not depend on z=y/x
  (problem was for y'= (y*%e^(x/y)-x)/x )
* graph: no animation is created, if server load in last minute is
    bigger than 2 
* minmax3d: check that the stationary point does not contains %r1 etc.
    like for the function x*x*(x*(%e**(-x*x-y*y)))
* integral: if we integrate all terms in a sum, we use map command, this makes 
    integaration of 2/(x^2+1)-1/(x+1)+1/(x-1) simpler, namely 
     -log(x+1)+2*atan(x)+log(x-1) instead of 4*(-log(x+1)/4+atan(x)/2+log(x-1)/4)
* integral: removed radcan before the function is integrated. This allows to evaluate 
    integral of 1/(sqrt(1-x^2)*acos(x)^3) in the form involving acos(x)^(-2).
    The integral of 1/(sqrt(1-x)*sqrt(1+x)*acos(x)^3) involves atan2 and a warning 
    is produced in this case.
* trapezoidal: if scaling in y for the picture is too large, metapost gives error 
   (arithmetic overflow) and hence we draw no picture in this case. This concenrs 
   functions like  1/(x^3+125) on the interval from 0 to 1
* trapezoidal: x coordinates for picture are translated into decimal numbers. this 
   solves the problem with integration from 1e-10 to ....
* geom: no parameters are allowed
* all: detailed error message if greek letter is used instead of pi or %pi on input

september 2008
* banach: nonliner equations using bisection and iterations, variable y is not alloed
* all: sinh, cosh, tanh, coth, .....  on blacklist
* fixed bug in second order ODE's: if decimals are used and if D is 0.0, 
   then D=0 is false

august 2008
* lde2: support for right hand  sides like x+exp(-2x)*sin(x)+cos(2x)   
    (sum of quazipolynomials)
* functions investigation: no factorization if the derivative is number
* integral: support for output into PDF, definite integral, automatical
     back substitution
* double integral: link to swap inside limits, if these limits are
    interchanged and error is generated
* TeX files (maw.tex): \rihgtskip is 0 pt plus 1 fill
* derivative: use power rule for derivative of 1/(sin(x)*cos(x) - 
    not qoutitent rule
* fixed bugs in javascripts in animations produced by transformation of graph

31.7.
* formconv upgraded to last CVS version (solved problems with
  conversion of -(2/sqrt(x)) into TeX)

29.7.
* double integral: added trigsimp if the input contains trigonometric functions
* derivative: added support for derivative of absolute value

28.7.
* integral hints cover R(sin(ax+b),cos(ax+b)) and many other patterns
  (composite functions with powers)

26.7.
* history contains links which show the result of the computation

25.7.
* updated to maxima-5.15.0 (compiled sources) with clisp (sid) and back to 5.13.0 
  (better perfomance)

21.7.
* gnuplot does not evaluate sqrt(x) fox negative x. Hence the graph of
  sqrt(x)*sqrt(x-1) is on the interval (1,infty) only (and not on the
  union with the interval (-infty,0)).

19.7.
* integral called from PDF files (ODE, definite integral): formconv is
   on as default
* test that the degree of Taylor polynomial is an integer (small than
   10) and the center is not a funcito nof x.
* trapezoidal rule: test that the number of subintervals is a number
   between 0 and 20.

18.7.
* geometrical applications of definite integral: if the region is outside 
   the bounds for the picture, the bounds are changed

17.7.
* double integral - picture for domain of integration

16.7.
* double integral - added links from integrals in PDF to integral
   assistant, made necessary changes in integral assistant
* all files - removed hardwired paths nad URLs, fixed bug with missing
   $mpost variable
* trapezoidal rule and geometrical applications: definite integral is
   evaluated using Newton Leibniz formula (model example
   for the problem is integrate(log(x^2+1),x,0,1) which fails as a
   definite integral in Maxima, but it is evaluated as indefinite
   integral)
* updated formconv to 0.8.8 - the cube root is drawn also for negative
   argument 
 
15.7.
* integral - added option to simplify numerator and denominator afre
  multiplying fraction, this allows to integrate functions like
  1/(sqrt(x)+sqrt(x+1))

13.7.
* Fixed english translation (domains of functions)

9.6.
* ODE: y'=exp(2*x-2*y) is solved as separable (maxima reports this
    equation as exact)
* Autonomous systems: support for passing stationary points computed
    by Maxima for further evaluation

27.5.
* ODE: if the ODE is not in the form y'=f(x,y), user can isolate y'
  first and then load into the corresponding form

5.5.
* double integral, 
* 1-st order homogeneous ODE equation, 
* more general right hand side for undetermined coefficients for second 
  order linear ODE

25.4. 
* minima and maxima in two variables: removing "stationary points" if 
  the function takes on complex values, such as log of negative number 
  (thanks to Marie Provaznikova and her students)

22.4. 
* integral: more and better hints, covers e.g. ln^2(x+4)  - substitution
   first and then integration by parts
* fixed bug in partial derivatives - missing ratsimp (thanks to Liiiza)
  and radcan (26.4.)

16.4. 
* function investigation: added freeof test if the equation has been
solved. This removes problem with ((2*(x^2))-log(x)) or (x+1)/atan(x)
* ODE: an error occurs and is logged if the evaluatin of integral is 
  terminanted. Model for the problem is y'=(2*cos(x)*sin(x-1))/(sin(x)+2)**3

13.4.
* more accurate hints in integral asssitant
* only the functions which modify the funciton are listed in integral
  assistant

11.4.
* function investiagtion: warning if arc-trig functions are used to
  solve the problem and some solutions are los. minor bugfix to filter
  out complex solutions

April 2008
* more hints in integral assistant, 
* new error messages in integral assistant ("can't integrate" and 
  "too long formula")
* links from PDF files with ODE's and definite integral into integral assistant

27.3.
* Better fix of the bug from tomorrow: used errcatch in new function 
  maw_solve, which replaces the original solve in some problems.
* Minor bugfix in matching patterns for substitution.
* Used our own mathtex server instead of slow is.mendelu.cz
* integral assistant accepts constants a and b

26.3.
* New version of formconv, some previous changes which are no more necessary
  with this new version (concerning acot function)
* More matching patterns for integral.
* Function investigation - fixed problem with error when solving solve(f,x)=0, 
  for example  if f(x)=acot(x).
  
25.3. 
* hints for substitution in indefinite integral, covers selected basic
  types

24.3.
* many changes in indefinite integral (hints for formulas and
  integration by parts and much more)

20.3.-22.3
* sqrt(x) function does not return value for negative x in calculator 
  for function investigation. This prevents to draw graph of a functions like
  sqrt(x+1)/sqrt(x) for x<-1. The solution is to replace sqrt by the function 
  mysqrt(x) = (x>=0)?sqrt(x):0/0, as suggested by Michael Hofmann.
* Support for volume of revolution. Improved routine which checks that the 
  problem to find area between two curves if well posed.
* Indefinite integral: automatical hints that intergration by parts or 
  expansion into partial fraction is a convenient tool. Improved
  integration by partial fraction, there are still problems with 
  expansion of 1/(x^3+2) into partial fractions - we get either no
  expansion or expansion with complex numbers :(

19.3.
* Regular expressions catch inequalitites which not sharp or writen badly 
  (like x,y>0 or 2x+y>9) and give a hint for few common problems 
  (x,y>0 => x>0 and y>0; 2x+y>9 => 2*x+y>9). 

18.3.
* Fixed bug in particular solution of second order LDE via undetermined 
  coefficients.
* Fixed missing parenthesis in integration by parts in integral
  assistant. Thanks to Mirek Machala.

15.3.-17.3
* graphs of elementary functions: fixed acot function (is continuous at 0), 
  accepts also other than natural logs
* PDF output for inequalities in one and two variables.

12.3.
* started to write logs in english
* derivative is able to handle functions like sin(a(2*x)*x^2)
* fixed few security problems
* fixed many things, hope nothing has been broken, only allowed funcitons 
  or parameters are a and b
* registering project on sourceforge

11.3.
* chybova hlaska pokud se nepodari vyresit nerovnici nebo soustavu
  (tj. pokud soustava nema reseni).
* oprava ztracene mezery v souboru ode.pl (reseni rovnice 
  y'=-cos(x)/sin(x)*y+x/sin(x) davalo chybu)
* oprava parametru pouzitych pro rozparsrovani funkce kvuli derivacim v 
  souborech derivace2.mac a derivace2y.mac (aa->aa[1] - thanks to 
  Harald Geyer)

10.3. 
* novy design stranek (prehlednejsi rozdeleni do tematickych skupin) 
* soustava linearnich nerovnic - zatim jenom v html

7.3. 
* Zobrazuji se jednotliva dilci reseni u definicniho oboru funkce dvou 
  promennych
* Definicni obor funkce jedne promenne 

6.3. 
* U definicniho oboru funkce dvou promennych se zobrazuji i podminky,
  ktere je nutno splnit.
* U hledani stac. bodu funkce dvou promennych je umoznem i vypocet v
  pripade, ze funkce obsahuje parametr (a,b, ...) - pridani promennych
  [x,y] do parametru prikazu solve.

5.3.
* derivace krok po kroku
* u urciteho integralu v geometrii, prubehu funkce a mozna jeste nekde 
  jinde se kontroluje, ze zadana funkce je funkci jedne promenne
* uprava zobrazovani definicniho oboru funkce dvou promennych, vysledek
  se zobrazuje v html strance, ne jako samostatny png soubor.
* negsumdispflag:false u neurciteho integralu

3.3.
* Urcity integral: funkce se kresli ne na intervalu (a,b), ale na
  (a-0.0000001,b+0.0000001), aby byla mensi pravdepodobnost ze vyjde
  log(-1) a aby se tim padem pekne nakreslil graf funkce x*(log(x))^2
* integral: konverze hranatych zavorek na kulate (hranate maji v maxime
   jiny  vyznam)

29.2.
* Integral: zpetna substituce, integral souctu
* Urcity integral: zahazuji se komplexni cisla, tohle resi 
  problem pri kresleni funkci jako arccos(x) nebo sqrt(1-x^2),
  odchytavaji se numericke chyby jako deleni nulou a logaritmus nuly,
  aby nevadily prikresleni grafu

26.2.
* Integral: u substituce se kontroluje, jestli se nepouziva uz jednou
  pouzite pismenko, anglicka verze

23.2.2008 
* Rada vylepseni do kalkulacky s neurcitym integralem a nahled
  zadani v prubehu funkce 
  
21.2.2008
* pridan "pruvodce neurcitym integralem", zatim jenom v cestine, stejne
  jako posunute grafy funkci.

20.2.2008
* pridan prikaz errcatch do filtru, ktery filtruje koreny funkce a
  jejich derivaci u prubehu. Po uprave filtru totiz daval prubeh funkce
  y=tan(x) chybu.

18.2.2008
* Grafy zakladnich elementarnich funkci v posunutem a natazenem tvaru
* Vylepsena detekce komplexnich korenu u prubehu, napriklad 
  x^4-10*x^2-1 hlasilo 4 koreny, ale jsou jenom dva. Pokud je koren moc
  slozity (TeXovsky zapis vic jak 200 znaku) netiskne se.

13.2.2008
* Nova verze programu formconv (resi napriklad problem s (x*log(x))^2) a
  zobrazuje se nahled vzorce v nekterych pripadech, kdy vstupni filtr
  zachyti problem v zapisu matematickeho vzorce (chybi zavorka za
  jemenem funkce a podobne)

9.2.2008
* Prubeh: opraveno derivovani funkci jako 1/2*(x+1/x), pri derivovani se 
  vytyka konstanta v citateli, pokud to jde. Drobne upravy chybovych
  hlasek. Pridano logexpand:false, aby se nasel i zaporny koren funce
  ln(x^2).
* Novy kalkulator: Lagrageuv interpolacni polynom 
* Opraveno zahazovani nerealnych korenu u ODR a u prubehu (zadny koren 
  rovnice x^4+1=0 se od ted uz netvari jako realny)
* MNC: kontrola zapomenutych nebo prebytecnych souradnic a prebytecnych 
  nebo chybejicich carek nebo stredniku
* Lepsi zobrazovani Taylorova polynomu (pridano pfeformat:true)
* prubeh a taylor: uprava, aby se nepouzival formconv (problemy s
  (x*ln(x))^2)
* prubeh: trigsimp se pouzije jenom, kdyz je v zadani trigonometricka
  nebo k ni inverzni funkce. To osetri nezadouci prevod log(x^2) na 
  2*log(x) treba pri derivovani funkce x*log(x^2).
* uprava vstupniho filtru: podrobnejsi chybove hlasky a zakazana
  desetinna cisla (program je nekdy prevadi na zlomky, coz muze vest ke 
  zmateni ctenare), osetreni zpetnych lomitek
* funkce dvou promennych: umi kreslit definicni obor

31.1.2008
* ODE: automaticky se zahazuji komplexni vysledky pri hledani
  konstatnich reseni separovatelne DR a byly opraveny drobne chybky.

30.1.2008 
* Vstupni filtr odchyti pokus pouzit jako oddelovac desetinnych
  mist carku misto tecky a vyvola srozumitelne chybove hlaseni.
* prubeh: Hezci kresleni asymptot (plna modra cara)
* prubeh: Opravena chyba zpusobena koncem radku pri detekci, zda je funkce
  polynom. Opravena kontrola, zda se da kratit: v nekterych pripadech
  davala falesnou chybovou hlasku.

27.1.2008
* pokud je tecka pritomna v jinem kontextu, nez jako oddelovac
  desetinnych mist, vyvola vstupni filtr odpovidajici chybove hlaseni
* prubeh: pokud je zadana racionalni lomena funkce, kde se da kratit,
  program odmitne vypocet a pozaduje zadani ve zkracene forme (citatel
  a jmenovatel nemaji stejne koreny). Zkraceny tvar zlomku je soucasti
  chybove hlasky.

26.1.2008
* prubeh: detekce, jestli zadana funkce je polynom nebo podil dvou
  polynomu a pokud ano, tak se provede detailnejsi analyza (definicni
  obor, body nespojitosti, asymptoty v nekonecnech a bodech
  nespojitosti, postup pri uprave derivace pokud jmenovatel ma vsechny 
  koreny stejne nasobnosti)

24.1.2008
* prubeh: oprava volani programu formconv - pridan parametr -r pri
  vykreslovani grafu (thanks to Zoltan Kovacs). Absence toho parametru
  zpusobovala, ze zlomky typu 1/2 byly pri kresleni grafu programem
  GNUplot povazovane za celociselne deleni a vysledkem byla nula

20.1.2008
* oprava mensi chyby, ktera zpusobovala chybu pri pouziti konstanty %pi
  ve vypoctech (omylem smazana mezera)
* u geometricke aplikace kontrola na spojitost funkci v krajnich bodech
* oprava filtru matematickych vyrazu, vyraz typu 4e^x nespusti
  vypocet, ale zobrazi varovani (zapomenute znamenko pro nasobeni)

19.1.2008
* metoda odhadu partikularniho reseni pro LDR druheho radu, kdy na prave 
  strane je polynom, nebo polynom v soucinu s exponencialni funkci

15.1.2008
* dve jazykove mutace
* uprava vetsiny kalkulatoru

10.1.2008
* bod kolem nehoz se dela Tayloruv polynom muze byt i %pi nebo %e a
  podobne
* nastavena restriktivni pravidla, co je a co neni mozno zapisovat do 
  formularu (pismena s diakritikou, recka pismena jina nez %pi, 
  hyperbolicke funkce a podobne)

9.1.2008
* filtr pi->%pi a osetreni absolutni hodnoty zapsane pomoci svislych car

7.1.2008
* css styly a jednotny vizualni styl html a PDF souboru
* uprava reseni ODE (nejdriv jako linearni, potom pripadne separace)

6.1.2008 
* lepsi separace promennych u ODE prvniho radu a chybova hlaska
  pokud Maxima rovnici nevyresi
* nova verze konverzniho programu formconv, osetruje problem ze obcas
  byly ve TeXovskem vystupu vynechane zavorky
* kodovani cestiny zmeneno na UTF-8
* kontrola parovosti zavorek a prazdnych retezcu
* logovani nekterych matematicky nekorektnich vyrazu do souboru

5.1.2008 
* Taylor: pridana kontrola, jestli je funkce v zadanem bode spojita,
  pokud ne, vypise se varovani. Oprava mensich chyb v TeXovskem ovladaci.

* MNC: Pridan filtr pro vyvolani chyby v pripade, kdy jsou na vstupu
  i jine znaky nez cisla a oddelovace

* Podorobnejsi chybove hlasky v pripade nekorektnich nebo nepovolenych
  dat na vstupu. 

4.1.2008
* NOVA APLIKACE: linearni diferencialni rovnice druheho radu
* Kalkulacka na prubeh funkce se snazi zobrazit i nulove body funkce
* Vstupni formulare byly upraveny aby varovaly uzivatele, pokud
  nenapise explicitne nasobeni a pokud nevyznaci kulatou zavorkou
  rozsah pusobnosti funkci jako sin, cos a podobne

3.1.2008
* Uprava souboru taylor.pl, aby nezjednodusoval zadanou funkci