@itemize @bullet
@item
-at most of complexity @math{O(n log n)}
+at most of complexity
+@tex
+$O(n\log n)$
+@end tex
+@ifnottex
+@math{O(n log n)}
+@end ifnottex
@item
algebraically correct, possibly except for a set of measure zero (e.g.
@math{x/x} is transformed to @math{1} although this is incorrect for @math{x=0})
The general rule is that when you construct expressions, GiNaC automatically
creates them in canonical form, which might differ from the form you typed in
your program. This may create some awkward looking output (@samp{-y+x} instead
-of @samp{y-x}) but allows for more efficient operation and usually yields
+of @samp{x-y}) but allows for more efficient operation and usually yields
some immediate simplifications.
@cindex @code{eval()}
@end ifnottex
@dots{}
@item @code{pseries} @tab Power Series, e.g. @math{x-1/6*x^3+1/120*x^5+O(x^7)}
-@item @code{function} @tab A symbolic function like @math{sin(2*x)}
+@item @code{function} @tab A symbolic function like
+@tex
+$\sin 2x$
+@end tex
+@ifnottex
+@math{sin(2*x)}
+@end ifnottex
@item @code{lst} @tab Lists of expressions @{@math{x}, @math{2*y}, @math{3+z}@}
@item @code{matrix} @tab @math{m}x@math{n} matrices of expressions
@item @code{relational} @tab A relation like the identity @math{x}@code{==}@math{y}
@item @code{varidx} @tab Index with variance
@item @code{spinidx} @tab Index with variance and dot (used in Weyl-van-der-Waerden spinor formalism)
@item @code{wildcard} @tab Wildcard for pattern matching
+@item @code{structure} @tab Template for user-defined classes
@end multitable
@end cartouche
@end multitable
@end cartouche
+@subsection Converting numbers
+
+Sometimes it is desirable to convert a @code{numeric} object back to a
+built-in arithmetic type (@code{int}, @code{double}, etc.). The @code{numeric}
+class provides a couple of methods for this purpose:
+
+@cindex @code{to_int()}
+@cindex @code{to_long()}
+@cindex @code{to_double()}
+@cindex @code{to_cl_N()}
+@example
+int numeric::to_int() const;
+long numeric::to_long() const;
+double numeric::to_double() const;
+cln::cl_N numeric::to_cl_N() const;
+@end example
+
+@code{to_int()} and @code{to_long()} only work when the number they are
+applied on is an exact integer. Otherwise the program will halt with a
+message like @samp{Not a 32-bit integer}. @code{to_double()} applied on a
+rational number will return a floating-point approximation. Both
+@code{to_int()/to_long()} and @code{to_double()} discard the imaginary
+part of complex numbers.
+
@node Constants, Fundamental containers, Numbers, Basic Concepts
@c node-name, next, previous, up
The GiNaC class @code{lst} serves for holding a @dfn{list} of arbitrary
expressions. They are not as ubiquitous as in many other computer algebra
packages, but are sometimes used to supply a variable number of arguments of
-the same type to GiNaC methods such as @code{subs()} and @code{to_rational()},
-so you should have a basic understanding of them.
+the same type to GiNaC methods such as @code{subs()} and some @code{matrix}
+constructors, so you should have a basic understanding of them.
Lists of up to 16 expressions can be directly constructed from single
expressions:
@example
ex matrix::determinant(unsigned algo=determinant_algo::automatic) const;
ex matrix::trace() const;
-ex matrix::charpoly(const symbol & lambda) const;
+ex matrix::charpoly(const ex & lambda) const;
@end example
The @samp{algo} argument of @code{determinant()} allows to select
@menu
* Information About Expressions::
+* Numerical Evaluation::
* Substituting Expressions::
* Pattern Matching and Advanced Substitutions::
* Applying a Function on Subexpressions::
@end menu
-@node Information About Expressions, Substituting Expressions, Methods and Functions, Methods and Functions
+@node Information About Expressions, Numerical Evaluation, Methods and Functions, Methods and Functions
@c node-name, next, previous, up
@section Getting information about expressions
for checking whether one expression is equal to another, or equal to zero,
respectively.
-@strong{Warning:} You will also find an @code{ex::compare()} method in the
-GiNaC header files. This method is however only to be used internally by
-GiNaC to establish a canonical sort order for terms, and using it to compare
-expressions will give very surprising results.
+@subsection Ordering expressions
+@cindex @code{ex_is_less} (class)
+@cindex @code{ex_is_equal} (class)
+@cindex @code{compare()}
+
+Sometimes it is necessary to establish a mathematically well-defined ordering
+on a set of arbitrary expressions, for example to use expressions as keys
+in a @code{std::map<>} container, or to bring a vector of expressions into
+a canonical order (which is done internally by GiNaC for sums and products).
+
+The operators @code{<}, @code{>} etc. described in the last section cannot
+be used for this, as they don't implement an ordering relation in the
+mathematical sense. In particular, they are not guaranteed to be
+antisymmetric: if @samp{a} and @samp{b} are different expressions, and
+@code{a < b} yields @code{false}, then @code{b < a} doesn't necessarily
+yield @code{true}.
+
+By default, STL classes and algorithms use the @code{<} and @code{==}
+operators to compare objects, which are unsuitable for expressions, but GiNaC
+provides two functors that can be supplied as proper binary comparison
+predicates to the STL:
+
+@example
+class ex_is_less : public std::binary_function<ex, ex, bool> @{
+public:
+ bool operator()(const ex &lh, const ex &rh) const;
+@};
+
+class ex_is_equal : public std::binary_function<ex, ex, bool> @{
+public:
+ bool operator()(const ex &lh, const ex &rh) const;
+@};
+@end example
+
+For example, to define a @code{map} that maps expressions to strings you
+have to use
+
+@example
+std::map<ex, std::string, ex_is_less> myMap;
+@end example
+
+Omitting the @code{ex_is_less} template parameter will introduce spurious
+bugs because the map operates improperly.
+
+Other examples for the use of the functors:
+
+@example
+std::vector<ex> v;
+// fill vector
+...
+
+// sort vector
+std::sort(v.begin(), v.end(), ex_is_less());
+
+// count the number of expressions equal to '1'
+unsigned num_ones = std::count_if(v.begin(), v.end(),
+ std::bind2nd(ex_is_equal(), 1));
+@end example
+
+The implementation of @code{ex_is_less} uses the member function
+
+@example
+int ex::compare(const ex & other) const;
+@end example
+
+which returns @math{0} if @code{*this} and @code{other} are equal, @math{-1}
+if @code{*this} sorts before @code{other}, and @math{1} if @code{*this} sorts
+after @code{other}.
-@node Substituting Expressions, Pattern Matching and Advanced Substitutions, Information About Expressions, Methods and Functions
+
+@node Numerical Evaluation, Substituting Expressions, Information About Expressions, Methods and Functions
+@c node-name, next, previous, up
+@section Numercial Evaluation
+@cindex @code{evalf()}
+
+GiNaC keeps algebraic expressions, numbers and constants in their exact form.
+To evaluate them using floating-point arithmetic you need to call
+
+@example
+ex ex::evalf(int level = 0) const;
+@end example
+
+@cindex @code{Digits}
+The accuracy of the evaluation is controlled by the global object @code{Digits}
+which can be assigned an integer value. The default value of @code{Digits}
+is 17. @xref{Numbers}, for more information and examples.
+
+To evaluate an expression to a @code{double} floating-point number you can
+call @code{evalf()} followed by @code{numeric::to_double()}, like this:
+
+@example
+@{
+ // Approximate sin(x/Pi)
+ symbol x("x");
+ ex e = series(sin(x/Pi), x == 0, 6);
+
+ // Evaluate numerically at x=0.1
+ ex f = evalf(e.subs(x == 0.1));
+
+ // ex_to<numeric> is an unsafe cast, so check the type first
+ if (is_a<numeric>(f)) @{
+ double d = ex_to<numeric>(f).to_double();
+ cout << d << endl;
+ // -> 0.0318256
+ @} else
+ // error
+@}
+@end example
+
+
+@node Substituting Expressions, Pattern Matching and Advanced Substitutions, Numerical Evaluation, Methods and Functions
@c node-name, next, previous, up
@section Substituting expressions
@cindex @code{subs()}
expressions via the @code{.subs()} method:
@example
-ex ex::subs(const ex & e);
-ex ex::subs(const lst & syms, const lst & repls);
+ex ex::subs(const ex & e, unsigned options = 0);
+ex ex::subs(const exmap & m, unsigned options = 0);
+ex ex::subs(const lst & syms, const lst & repls, unsigned options = 0);
@end example
In the first form, @code{subs()} accepts a relational of the form
If you specify multiple substitutions, they are performed in parallel, so e.g.
@code{subs(lst(x == y, y == x))} exchanges @samp{x} and @samp{y}.
-The second form of @code{subs()} takes two lists, one for the objects to be
+The second form of @code{subs()} takes an @code{exmap} object which is a
+pair associative container that maps expressions to expressions (currently
+implemented as a @code{std::map}). This is the most efficient one of the
+three @code{subs()} forms and should be used when the number of objects to
+be substituted is large or unknown.
+
+Using this form, the second example from above would look like this:
+
+@example
+@{
+ symbol x("x"), y("y");
+ ex e2 = x*y + x;
+
+ exmap m;
+ m[x] = -2;
+ m[y] = 4;
+ cout << "e2(-2, 4) = " << e2.subs(m) << endl;
+@}
+@end example
+
+The third form of @code{subs()} takes two lists, one for the objects to be
replaced and one for the expressions to be substituted (both lists must
contain the same number of elements). Using this form, you would write
-@code{subs(lst(x, y), lst(y, x))} to exchange @samp{x} and @samp{y}.
+
+@example
+@{
+ symbol x("x"), y("y");
+ ex e2 = x*y + x;
+
+ cout << "e2(-2, 4) = " << e2.subs(lst(x, y), lst(-2, 4)) << endl;
+@}
+@end example
+
+The optional last argument to @code{subs()} is a combination of
+@code{subs_options} flags. There are two options available:
+@code{subs_options::no_pattern} disables pattern matching, which makes
+large @code{subs()} operations significantly faster if you are not using
+patterns. The second option, @code{subs_options::algebraic} enables
+algebraic substitutions in products and powers.
+@ref{Pattern Matching and Advanced Substitutions}, for more information
+about patterns and algebraic substitutions.
@code{subs()} performs syntactic substitution of any complete algebraic
object; it does not try to match sub-expressions as is demonstrated by the
@end example
@subsection Algebraic substitutions
-The @code{subs()} method has an extra, optional, argument. This argument can
-be used to pass one of the @code{subs_options} to it. The only option that is
-currently available is the @code{subs_algebraic} option which affects
-products and powers. If you want to substitute some factors of a product, you
-only need to list these factors in your pattern. Furthermore, if an (integer)
-power of some expression occurs in your pattern and in the expression that you
-want the substitution to occur in, it can be substituted as many times as
-possible, without getting negative powers.
+Supplying the @code{subs_options::algebraic} option to @code{subs()}
+enables smarter, algebraic substitutions in products and powers. If you want
+to substitute some factors of a product, you only need to list these factors
+in your pattern. Furthermore, if an (integer) power of some expression occurs
+in your pattern and in the expression that you want the substitution to occur
+in, it can be substituted as many times as possible, without getting negative
+powers.
An example clarifies it all (hopefully):
@example
cout << (a*a*a*a+b*b*b*b+pow(x+y,4)).subs(wild()*wild()==pow(wild(),3),
- subs_options::subs_algebraic) << endl;
+ subs_options::algebraic) << endl;
// --> (y+x)^6+b^6+a^6
-cout << ((a+b+c)*(a+b+c)).subs(a+b==x,subs_options::subs_algebraic) << endl;
+cout << ((a+b+c)*(a+b+c)).subs(a+b==x,subs_options::algebraic) << endl;
// --> (c+b+a)^2
// Powers and products are smart, but addition is just the same.
-cout << ((a+b+c)*(a+b+c)).subs(a+b+wild()==x+wild(), subs_options::subs_algebraic)
+cout << ((a+b+c)*(a+b+c)).subs(a+b+wild()==x+wild(), subs_options::algebraic)
<< endl;
// --> (x+c)^2
// As I said: addition is just the same.
-cout << (pow(a,5)*pow(b,7)+2*b).subs(b*b*a==x,subs_options::subs_algebraic) << endl;
+cout << (pow(a,5)*pow(b,7)+2*b).subs(b*b*a==x,subs_options::algebraic) << endl;
// --> x^3*b*a^2+2*b
-cout << (pow(a,-5)*pow(b,-7)+2*b).subs(1/(b*b*a)==x,subs_options::subs_algebraic)
+cout << (pow(a,-5)*pow(b,-7)+2*b).subs(1/(b*b*a)==x,subs_options::algebraic)
<< endl;
// --> 2*b+x^3*b^(-1)*a^(-2)
-cout << (4*x*x*x-2*x*x+5*x-1).subs(x==a,subs_options::subs_algebraic) << endl;
+cout << (4*x*x*x-2*x*x+5*x-1).subs(x==a,subs_options::algebraic) << endl;
// --> -1-2*a^2+4*a^3+5*a
cout << (4*x*x*x-2*x*x+5*x-1).subs(pow(x,wild())==pow(a,wild()),
- subs_options::subs_algebraic) << endl;
+ subs_options::algebraic) << endl;
// --> -1+5*x+4*x^3-2*x^2
// You should not really need this kind of patterns very often now.
// But perhaps this it's-not-a-bug-it's-a-feature (c/sh)ould still change.
cout << ex(sin(1+sin(x))).subs(sin(wild())==cos(wild()),
- subs_options::subs_algebraic) << endl;
+ subs_options::algebraic) << endl;
// --> cos(1+cos(x))
cout << expand((a*sin(x+y)*sin(x+y)+a*cos(x+y)*cos(x+y)+b)
.subs((pow(cos(wild()),2)==1-pow(sin(wild()),2)),
- subs_options::subs_algebraic)) << endl;
+ subs_options::algebraic)) << endl;
// --> b+a
@end example
To bring an expression into expanded form, its method
@example
-ex ex::expand();
+ex ex::expand(unsigned options = 0);
@end example
may be called. In our example above, this corresponds to @math{4*x*y +
The two functions
@example
-ex quo(const ex & a, const ex & b, const symbol & x);
-ex rem(const ex & a, const ex & b, const symbol & x);
+ex quo(const ex & a, const ex & b, const ex & x);
+ex rem(const ex & a, const ex & b, const ex & x);
@end example
compute the quotient and remainder of univariate polynomials in the variable
The additional function
@example
-ex prem(const ex & a, const ex & b, const symbol & x);
+ex prem(const ex & a, const ex & b, const ex & x);
@end example
computes the pseudo-remainder of @samp{a} and @samp{b} which satisfies
The methods
@example
-ex ex::unit(const symbol & x);
-ex ex::content(const symbol & x);
-ex ex::primpart(const symbol & x);
+ex ex::unit(const ex & x);
+ex ex::content(const ex & x);
+ex ex::primpart(const ex & x);
@end example
return the unit part, content part, and primitive polynomial of a multivariate
above. You do this by calling
@example
-ex ex::to_polynomial(lst &l);
+ex ex::to_polynomial(exmap & m);
+ex ex::to_polynomial(lst & l);
@end example
or
@example
-ex ex::to_rational(lst &l);
+ex ex::to_rational(exmap & m);
+ex ex::to_rational(lst & l);
@end example
-on the expression to be converted. The supplied @code{lst} will be filled
-with the generated temporary symbols and their replacement expressions in
-a format that can be used directly for the @code{subs()} method. It can also
-already contain a list of replacements from an earlier application of
-@code{.to_polynomial()} or @code{.to_rational()}, so it's possible to use
-it on multiple expressions and get consistent results.
+on the expression to be converted. The supplied @code{exmap} or @code{lst}
+will be filled with the generated temporary symbols and their replacement
+expressions in a format that can be used directly for the @code{subs()}
+method. It can also already contain a list of replacements from an earlier
+application of @code{.to_polynomial()} or @code{.to_rational()}, so it's
+possible to use it on multiple expressions and get consistent results.
The difference betwerrn @code{.to_polynomial()} and @code{.to_rational()}
is probably best illustrated with an example:
ex a = pow(sin(x), 2) - pow(cos(x), 2);
ex b = sin(x) + cos(x);
ex q;
- lst l;
- divide(a.to_polynomial(l), b.to_polynomial(l), q);
- cout << q.subs(l) << endl;
+ exmap m;
+ divide(a.to_polynomial(m), b.to_polynomial(m), q);
+ cout << q.subs(m) << endl;
@}
@end example
@item @code{Order(x)}
@tab order term function in truncated power series
@cindex @code{Order()}
+@item @code{Li(n,x)}
+@tab polylogarithm
+@cindex @code{Li()}
+@item @code{S(n,p,x)}
+@tab Nielsen's generalized polylogarithm
+@cindex @code{S()}
+@item @code{H(m_lst,x)}
+@tab harmonic polylogarithm
+@cindex @code{H()}
+@item @code{Li(m_lst,x_lst)}
+@tab multiple polylogarithm
+@cindex @code{Li()}
+@item @code{mZeta(m_lst)}
+@tab multiple zeta value
+@cindex @code{mZeta()}
@end multitable
@end cartouche
git://www.ginac.de / ginac.git / blobdiff