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5.1 nary | ||
5.2 nofix | ||
5.3 operator | ||
5.4 postfix | ||
5.5 prefix | ||
5.6 Definitions for Operators |
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An nary
operator is used to denote a function of any number of
arguments, each of which is separated by an occurrence of the
operator, e.g. A+B or A+B+C. The nary("x")
function is a syntax
extension function to declare x to be an nary
operator.
Functions may be declared to be
nary
. If declare(j,nary);
is done, this tells the simplifier to
simplify, e.g. j(j(a,b),j(c,d))
to j(a, b, c, d)
.
See also syntax
.
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nofix
operators are used to denote functions of no arguments.
The mere presence of such an operator in a command will cause the
corresponding function to be evaluated. For example, when one types
"exit;" to exit from a Maxima break, "exit" is behaving similar to a
nofix
operator. The function nofix("x")
is a syntax extension
function which declares x to be a nofix
operator.
See also syntax
.
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See operators
.
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postfix
operators like the prefix
variety denote functions
of a single argument, but in this case the argument immediately
precedes an occurrence of the operator in the input string, e.g. 3! .
The postfix("x")
function is a syntax extension function to declare x
to be a postfix
operator.
See also syntax
.
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A prefix
operator is one which signifies a function of one
argument, which argument immediately follows an occurrence of the
operator. prefix("x")
is a syntax extension function to declare x to
be a prefix
operator.
See also syntax
.
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The factorial operator.
For any complex number x
(including integer, rational, and real numbers) except for
negative integers, x!
is defined as gamma(x+1)
.
For an integer x
, x!
simplifies to the product of the integers from 1 to x
inclusive.
0!
simplifies to 1.
For a floating point number x
, x!
simplifies to the value of gamma (x+1)
.
For x
equal to n/2
where n
is an odd integer,
x!
simplifies to a rational factor times sqrt (%pi)
(since gamma (1/2)
is equal to sqrt (%pi)
).
If x
is anything else,
x!
is not simplified.
The variables
factlim
, minfactorial
, and factcomb
control the simplification
of expressions containing factorials.
The functions gamma
, bffac
, and cbffac
are varieties of the gamma function.
makegamma
substitutes gamma
for factorials and related functions.
See also binomial
.
factlim
.
(%i1) factlim: 10$ (%i2) [0!, (7/2)!, 4.77!, 8!, 20!]; 105 sqrt(%pi) (%o2) [1, -------------, 81.44668037931193, 40320, 20!] 16 |
(%i1) [(%i + 1)!, %pi!, %e!, (cos(1) + sin(1))!]; (%o1) [(%i + 1)!, %pi!, %e!, (sin(1) + cos(1))!] (%i2) ev (%, numer, %enumer); (%o2) [(%i + 1)!, 7.188082728976031, 4.260820476357003, 1.227580202486819] |
(%i1) kill (foo)$ (%i2) foo!; (%o2) foo! |
x!
may be replaced even in a quoted expression.
(%i1) '([0!, (7/2)!, 4.77!, 8!, 20!]); 105 sqrt(%pi) (%o1) [1, -------------, 81.44668037931193, 40320, 20!] 16 |
The double factorial operator.
For an integer, float, or rational number n
,
n!!
evaluates to the product n (n-2) (n-4) (n-6) ... (n - 2 (k-1))
where k
is equal to entier (n/2)
,
that is, the largest integer less than or equal to n/2
.
Note that this definition does not coincide with other published definitions
for arguments which are not integers.
For an even (or odd) integer n
, n!!
evaluates to the product of
all the consecutive even (or odd) integers from 2 (or 1) through n
inclusive.
For an argument n
which is not an integer, float, or rational,
n!!
yields a noun form genfact (n, n/2, 2)
.
Represents the negation of syntactic equality =
.
Note that because of the rules for evaluation of predicate expressions
(in particular because not expr
causes evaluation of expr),
not a = b
is not equivalent to a # b
in some cases.
Examples:
(%i1) a = b; (%o1) a = b (%i2) is (a = b); (%o2) false (%i3) a # b; (%o3) a # b (%i4) not a = b; (%o4) true (%i5) is (a # b); (%o5) true (%i6) is (not a = b); (%o6) true |
The dot operator, for matrix (non-commutative) multiplication. When "." is used in this way, spaces should be left on both sides of it, e.g. A . B. This distinguishes it plainly from a decimal point in a floating point number.
See also
dot
,
dot0nscsimp
,
dot0simp
,
dot1simp
,
dotassoc
,
dotconstrules
,
dotdistrib
,
dotexptsimp
,
dotident
,
and
dotscrules
.
The assignment operator. E.g. A:3 sets the variable A to 3.
Assignment operator. :: assigns the value of the expression on its right to the value of the quantity on its left, which must evaluate to an atomic variable or subscripted variable.
Macro function definition operator.
::=
defines a function (called a "macro" for historical reasons)
which quotes its arguments,
and the expression which it returns (called the "macro expansion")
is evaluated in the context from which the macro was called.
A macro function is otherwise the same as an ordinary function.
macroexpand
returns a macro expansion (without evaluating it).
macroexpand (foo (x))
followed by ''%
is equivalent to foo (x)
when foo
is a macro function.
::=
puts the name of the new macro function onto the global list macros
.
kill
, remove
, and remfunction
unbind macro function definitions
and remove names from macros
.
fundef
or dispfun
return a macro function definition
or assign it to a label, respectively.
Macro functions commonly contain buildq
and splice
expressions to construct an expression,
which is then evaluated.
Examples
A macro function quotes its arguments,
so message (1) shows y - z
, not the value of y - z
.
The macro expansion (the quoted expression '(print ("(2) x is equal to", x))
is evaluated in the context from which the macro was called,
printing message (2).
(%i1) x: %pi; (%o1) %pi (%i2) y: 1234; (%o2) 1234 (%i3) z: 1729 * w; (%o3) 1729 w (%i4) printq1 (x) ::= block (print ("(1) x is equal to", x), '(print ("(2) x is equal to", x))); (%o4) printq1(x) ::= block(print("(1) x is equal to", x), '(print("(2) x is equal to", x))) (%i5) printq1 (y - z); (1) x is equal to y - z (2) x is equal to %pi (%o5) %pi |
An ordinary function evaluates is arguments, so message (1) shows the value of y - z
.
The return value is not evaluated, so message (2) is not printed
until the explicit evaluation ''%
.
(%i1) x: %pi; (%o1) %pi (%i2) y: 1234; (%o2) 1234 (%i3) z: 1729 * w; (%o3) 1729 w (%i4) printe1 (x) := block (print ("(1) x is equal to", x), '(print ("(2) x is equal to", x))); (%o4) printe1(x) := block(print("(1) x is equal to", x), '(print("(2) x is equal to", x))) (%i5) printe1 (y - z); (1) x is equal to 1234 - 1729 w (%o5) print((2) x is equal to, x) (%i6) ''%; (2) x is equal to %pi (%o6) %pi |
macroexpand
returns a macro expansion.
macroexpand (foo (x))
followed by ''%
is equivalent to foo (x)
when foo
is a macro function.
(%i1) x: %pi; (%o1) %pi (%i2) y: 1234; (%o2) 1234 (%i3) z: 1729 * w; (%o3) 1729 w (%i4) g (x) ::= buildq ([x], print ("x is equal to", x)); (%o4) g(x) ::= buildq([x], print("x is equal to", x)) (%i5) macroexpand (g (y - z)); (%o5) print(x is equal to, y - z) (%i6) ''%; x is equal to 1234 - 1729 w (%o6) 1234 - 1729 w (%i7) g (y - z); x is equal to 1234 - 1729 w (%o7) 1234 - 1729 w |
The function definition operator. E.g. f(x):=sin(x)
defines
a function f
.
denotes an equation to Maxima. To the pattern matcher in Maxima it denotes a total relation that holds between two expressions if and only if the expressions are syntactically identical.
The negation of =
is represented by #
.
Note that because of the rules for evaluation of predicate expressions
(in particular because not expr
causes evaluation of expr),
not a = b
is not equivalent to a # b
in some cases.
The logical conjunction operator.
and
is an n-ary infix operator;
its operands are Boolean expressions, and its result is a Boolean value.
and
forces evaluation (like is
) of one or more operands,
and may force evaluation of all operands.
Operands are evaluated in the order in which they appear.
and
evaluates only as many of its operands as necessary to determine the result.
If any operand is false
,
the result is false
and no further operands are evaluated.
The global flag prederror
governs the behavior of and
when an evaluated operand cannot be determined to be true
or false
.
and
prints an error message when prederror
is true
.
Otherwise, and
returns unknown
.
and
is not commutative:
a and b
might not be equal to b and a
due to the treatment of indeterminate operands.
The logical disjunction operator.
or
is an n-ary infix operator;
its operands are Boolean expressions, and its result is a Boolean value.
or
forces evaluation (like is
) of one or more operands,
and may force evaluation of all operands.
Operands are evaluated in the order in which they appear.
or
evaluates only as many of its operands as necessary to determine the result.
If any operand is true
,
the result is true
and no further operands are evaluated.
The global flag prederror
governs the behavior of or
when an evaluated operand cannot be determined to be true
or false
.
or
prints an error message when prederror
is true
.
Otherwise, or
returns unknown
.
or
is not commutative:
a or b
might not be equal to b or a
due to the treatment of indeterminate operands.
The logical negation operator.
not
is a prefix operator;
its operand is a Boolean expression, and its result is a Boolean value.
not
forces evaluation (like is
) of its operand.
The global flag prederror
governs the behavior of not
when its operand cannot be determined to be true
or false
.
not
prints an error message when prederror
is true
.
Otherwise, not
returns unknown
.
Returns the absolute value expr. If expr is complex, returns the complex modulus of expr.
If declare(f,additive)
has been executed, then:
(1) If f
is univariate, whenever the simplifier encounters f
applied
to a sum, f
will be distributed over that sum. I.e. f(y+x)
will
simplify to f(y)+f(x)
.
(2) If f
is a function of 2 or more arguments, additivity is defined as
additivity in the first argument to f
, as in the case of sum
or
integrate
, i.e. f(h(x)+g(x),x)
will simplify to f(h(x),x)+f(g(x),x)
.
This simplification does not occur when f
is applied to expressions of
the form sum(x[i],i,lower-limit,upper-limit)
.
works with the part
commands (i.e. part
, inpart
, substpart
,
substinpart
, dpart
, and lpart
). For example,
(%i1) expr: e+d+c+b+a$ (%i2) part (expr, [2, 5]); (%o2) d + a |
while
(%i3) part (expr, allbut (2, 5)); (%o3) e + c + b |
It also works with the kill
command,
kill (allbut (name_1, ..., name_k)) |
will do a kill (all)
except it will not
kill
the names specified. Note: name_i
means a name such as function
name such as u
, f
, foo
, or g
, not an infolist such as functions
.
If declare(h,antisymmetric)
is done, this tells the
simplifier that h
is antisymmetric. E.g. h(x,z,y)
will simplify to
- h(x, y, z)
. That is, it will give (-1)^n times the result given by
symmetric
or commutative
, where n is the number of interchanges of two
arguments necessary to convert it to that form.
Returns the complex absolute value (the complex modulus) of expr.
When x is a real number, return the least integer that is greater than or equal to x.
If x is a constant expression (10 * %pi
, for example),
ceiling
evaluates x using big floating point numbers, and
applies ceiling
to the resulting big float. Because ceiling
uses
floating point evaluation, it's possible, although unlikely,
that ceiling
could return an erroneous value for constant
inputs. To guard against errors, the floating point evaluation
is done using three values for fpprec
.
For non-constant inputs, ceiling
tries to return a simplified
value. Here are examples of the simplifications that ceiling
knows about:
(%i1) ceiling(ceiling(x)); (%o1) ceiling(x) (%i2) ceiling(floor(x)); (%o2) floor(x) (%i3) declare(n,integer)$ (%i4) [ceiling(n), ceiling(abs(n)), ceiling(max(n,6))]; (%o4) [n, abs(n), max(n,6)] (%i5) assume(x > 0, x < 1)$ (%i6) ceiling(x); (%o6) 1 (%i7) tex(ceiling(a)); $$\left \lceil a \right \rceil$$ |
The function ceiling
does not automatically map over lists or matrices.
Finally, for all inputs that are manifestly complex, ceiling
returns
a noun form.
If the range of a function is a subset of the integers, it can be
declared to be integervalued
. Both the ceiling
and floor
functions
can use this information; for example:
(%i1) declare(f,integervalued)$ (%i2) floor(f(x)); (%o2) f(x) (%i3) ceiling(f(x) -1); (%o3) f(x)-1 |
Return 0 when the predicate p evaluates to false
; return
1 when the predicate evaluates to true
. When the predicate
evaluates to something other than true
or false
(unknown),
return a noun form.
Examples:
(%i1) charfun(x<1); (%o1) charfun(x<1) (%i2) subst(x=-1,%); (%o2) 1 (%i3) e : charfun('"and"(-1 < x, x < 1))$ (%i4) [subst(x=-1,e), subst(x=0,e), subst(x=1,e)]; (%o4) [0,1,0] |
If declare(h,commutative)
is done, this tells the
simplifier that h
is a commutative function. E.g. h(x,z,y)
will
simplify to h(x, y, z)
. This is the same as symmetric
.
Return a comparison operator op
(<
, <=
, >
, >=
, =
, or #
) such that
is (x op y)
evaluates to true;
when either x or y depends on %i
and
x # y
, return notcomparable
;
when there is no such operator or
Maxima isn't able to determine the operator, return unknown
.
Examples:
(%i1) compare(1,2); (%o1) < (%i2) compare(1,x); (%o2) unknown (%i3) compare(%i,%i); (%o3) = (%i4) compare(%i,%i+1); (%o4) notcomparable (%i5) compare(1/x,0); (%o5) # (%i6) compare(x,abs(x)); (%o6) <= |
The function compare
doesn't try to determine whether the real domains of
its arguments are nonempty; thus
(%i1) compare(acos(x^2+1), acos(x^2+1) + 1); (%o1) < |
The real domain of acos (x^2 + 1)
is empty.
Returns the largest integer less than or equal to x where x is numeric. fix
(as in
fixnum
) is a synonym for this, so fix(x)
is precisely the same.
Used with an is
, returns true
(or false
) if
and only if expr_1 and expr_2 are equal (or not equal) for all possible
values of their variables (as determined by ratsimp
). Thus
is (equal ((x + 1)^2, x^2 + 2*x + 1))
returns true
whereas if x
is unbound
is ((x + 1)^2 = x^2 + 2*x + 1)
returns false
. Note also that is(rat(0)=0)
yields false
but is (equal (rat(0), 0))
yields true
.
If a determination
can't be made, then is (equal (a, b))
returns a simplified but equivalent expression,
whereas is (a=b)
always returns either true
or false
.
All variables occurring in expr_1 and expr_2 are presumed to be real valued.
The negation of equal
is notequal
.
Note that because of the rules for evaluation of predicate expressions
(in particular because not expr
causes evaluation of expr),
notequal
is not equivalent to not equal
in some cases.
ev (expr, pred)
is equivalent to is (expr)
.
(%i1) is (x^2 >= 2*x - 1); (%o1) true (%i2) assume (a > 1); (%o2) [a > 1] (%i3) is (log (log (a+1) + 1) > 0 and a^2 + 1 > 2*a); (%o3) true |
When x is a real number, return the largest integer that is less than or equal to x.
If x is a constant expression (10 * %pi
, for example),
floor
evaluates x using big floating point numbers, and
applies floor to the resulting big float. Because floor uses
floating point evaluation, it's possible, although unlikely,
that floor
could return an erroneous value for constant
inputs. To guard against errors, the floating point evaluation
is done using three values for fpprec
.
For non-constant inputs, floor
tries to return a simplified
value. Here are examples of the simplifications that floor
knows about:
(%i1) floor(ceiling(x)); (%o1) ceiling(x) (%i2) floor(floor(x)); (%o2) floor(x) (%i3) declare(n,integer)$ (%i3) [floor(n), floor(abs(n)), floor(min(n,6))]; (%o4) [n,abs(n),min(n,6)] (%i4) assume(x > 0, x < 1)$ (%i5) floor(x); (%o5) 0 (%i6) tex(floor(a); $$\left \lfloor a \right \rfloor$$ |
The function floor
does not automatically map over lists or matrices.
Finally, for all inputs that are manifestly complex, floor
returns
a noun form.
If the range of a function is a subset of the integers, it can be
declared to be integervalued
. Both the ceiling
and floor
functions
can use this information; for example:
(%i1) declare(f,integervalued)$ (%i2) floor(f(x)); (%o2) f(x) (%i3) ceiling(f(x) -1); (%o3) f(x)-1 |
Represents the negation of equal (expr_1, expr_2)
.
Note that because of the rules for evaluation of predicate expressions
(in particular because not expr
causes evaluation of expr),
notequal
is not equivalent to not equal
in some cases.
Examples:
(%i1) equal (a, b); (%o1) equal(a, b) (%i2) maybe (equal (a, b)); (%o2) unknown (%i3) notequal (a, b); (%o3) notequal(a, b) (%i4) not equal (a, b); `macsyma' was unable to evaluate the predicate: equal(a, b) -- an error. Quitting. To debug this try debugmode(true); (%i5) maybe (notequal (a, b)); (%o5) unknown (%i6) maybe (not equal (a, b)); (%o6) unknown (%i7) assume (a > b); (%o7) [a > b] (%i8) equal (a, b); (%o8) equal(a, b) (%i9) maybe (equal (a, b)); (%o9) false (%i10) notequal (a, b); (%o10) notequal(a, b) (%i11) not equal (a, b); (%o11) true (%i12) maybe (notequal (a, b)); (%o12) true (%i13) maybe (not equal (a, b)); (%o13) true |
As an argument in a call to ev (expr)
,
eval
causes an extra evaluation of expr.
See ev
.
Returns true
if expr is an even integer.
false
is returned in all other cases.
A synonym for entier (x)
.
Similar to map
, but fullmap
keeps mapping
down all subexpressions until the main operators are no longer the
same.
fullmap
is used by the Maxima
simplifier for certain matrix manipulations; thus, Maxima sometimes generates
an error message concerning fullmap
even though fullmap
was not
explicitly called by the user.
(%i1) a + b*c$ (%i2) fullmap (g, %); (%o2) g(b) g(c) + g(a) (%i3) map (g, %th(2)); (%o3) g(b c) + g(a) |
Similar to fullmap
, but fullmapl
only maps onto
lists and matrices.
(%i1) fullmapl ("+", [3, [4, 5]], [[a, 1], [0, -1.5]]); (%o1) [[a + 3, 4], [4, 3.5]] |
Attempts to determine whether the predicate expr
is provable from the facts in the assume
database.
If the predicate is provably true
or false
,
is
returns true
or false
, respectively.
Otherwise, the return value is controlled by the global flag prederror
.
When prederror
is false
, is
returns unknown
for
a predicate which cannot be proven nor disproven,
and reports an error otherwise.
See also assume
, facts
, and maybe
.
Examples:
is
causes evaluation of predicates.
(%i1) %pi > %e; (%o1) %pi > %e (%i2) is (%pi > %e); (%o2) true |
is
attempts to derive predicates from the assume
database.
(%i1) assume (a > b); (%o1) [a > b] (%i2) assume (b > c); (%o2) [b > c] (%i3) is (a < b); (%o3) false (%i4) is (a > c); (%o4) true (%i5) is (equal (a, c)); (%o5) false |
If is
can neither prove nor disprove a predicate from the assume
database,
the global flag prederror
governs the behavior of is
.
(%i1) assume (a > b); (%o1) [a > b] (%i2) prederror: true$ (%i3) is (a > 0); `macsyma' was unable to evaluate the predicate: a > 0 -- an error. Quitting. To debug this try debugmode(true); (%i4) prederror: false$ (%i5) is (a > 0); (%o5) unknown |
Attempts to determine whether the predicate expr
is provable from the facts in the assume
database.
If the predicate is provably true
or false
,
maybe
returns true
or false
, respectively.
Otherwise, maybe
returns unknown
.
maybe
is functionally equivalent to is
with prederror: false
,
but the result is computed without actually assigning a value to prederror
.
See also assume
, facts
, and is
.
Examples:
(%i1) maybe (x > 0); (%o1) unknown (%i2) assume (x > 1); (%o2) [x > 1] (%i3) maybe (x > 0); (%o3) true |
Returns the "integer square root" of the absolute value of x, which is an integer.
When L is a list or a set, return apply ('max, args (L))
. When L isn't a
list or a set, signal an error.
When L is a list or a set, return apply ('min, args (L))
. When L isn't a
list or a set, signal an error.
Return a simplified value for the maximum of the expressions x_1 through x_n.
When get (trylevel, maxmin)
, is 2 or greater, max
uses the simplification
max (e, -e) --> |e|
. When get (trylevel, maxmin)
is 3 or greater, max tries
to eliminate expressions that are between two other arguments; for example,
max (x, 2*x, 3*x) --> max (x, 3*x)
. To set the value of trylevel
to 2, use
put (trylevel, 2, maxmin)
.
Return a simplified value for the minimum of the expressions x_1
through x_n
.
When get (trylevel, maxmin)
, is 2 or greater, min
uses the simplification
min (e, -e) --> -|e|
. When get (trylevel, maxmin)
is 3 or greater, min
tries
to eliminate expressions that are between two other arguments; for example,
min (x, 2*x, 3*x) --> min (x, 3*x)
. To set the value of trylevel
to 2, use
put (trylevel, 2, maxmin)
.
Converts the polynomial p to a modular representation
with respect to the current modulus which is the value of the variable
modulus
.
polymod (p, m)
specifies a modulus m to be used
instead of the current value of modulus
.
See modulus
.
If x and y are real numbers and y is nonzero,
return x - y * floor(x / y)
.
Further for all real x, we have mod (x, 0) = x
. For a discussion of
the definition mod (x, 0) = x
, see Section 3.4, of "Concrete Mathematics,"
by Graham, Knuth, and Patashnik. The function mod (x, 1)
is a sawtooth function with period 1 with mod (1, 1) = 0
and
mod (0, 1) = 0
.
To find the principal argument (a number in the interval (-%pi, %pi]
) of a
complex number, use the function x |-> %pi - mod (%pi - x, 2*%pi)
, where
x is an argument.
When x and y are constant expressions (10 * %pi
, for example), mod
uses the same big float evaluation scheme that floor
and ceiling
uses.
Again, it's possible, although unlikely, that mod
could return an
erroneous value in such cases.
For nonnumerical arguments x or y, mod
knows several simplification
rules:
(%i1) mod(x,0); (%o1) x (%i2) mod(a*x,a*y); (%o2) a*mod(x,y) (%i3) mod(0,x); (%o3) 0 |
is true
if expr is an odd integer.
false
is returned in all other cases.
As an argument in a call to ev (expr)
,
pred
causes predicates (expressions which evaluate to true
or false
) to be evaluated.
See ev
.
A random state object represents the state of the random number generator. The state comprises 627 32-bit words.
make_random_state (n)
returns a new random state object
created from an integer seed value equal to n modulo 2^32.
n may be negative.
make_random_state (s)
returns a copy of the random state s.
make_random_state (true)
returns a new random state object,
using the current computer clock time as the seed.
make_random_state (false)
returns a copy of the current state
of the random number generator.
Copies s to the random number generator state.
set_random_state
always returns done
.
Returns a pseudorandom number. If x is an integer, random (x)
returns an
integer from 0 through x - 1
inclusive. If x is a floating point number,
random (x)
returns a nonnegative floating point number less than x.
random
complains with an error if x is neither an integer nor a float,
or if x is not positive.
The functions make_random_state
and set_random_state
maintain the state of the random number generator.
The Maxima random number generator is an implementation of the Mersenne twister MT 19937.
Examples:
(%i1) s1: make_random_state (654321)$ (%i2) set_random_state (s1); (%o2) done (%i3) random (1000); (%o3) 768 (%i4) random (9573684); (%o4) 7657880 (%i5) random (2^75); (%o5) 11804491615036831636390 (%i6) s2: make_random_state (false)$ (%i7) random (1.0); (%o7) .2310127244107132 (%i8) random (10.0); (%o8) 4.394553645870825 (%i9) random (100.0); (%o9) 32.28666704056853 (%i10) set_random_state (s2); (%o10) done (%i11) random (1.0); (%o11) .2310127244107132 (%i12) random (10.0); (%o12) 4.394553645870825 (%i13) random (100.0); (%o13) 32.28666704056853 |
Convert all double floats and big floats in the Maxima expression
expr to their exact rational equivalents. If you are not familiar with
the binary representation of floating point numbers, you might
be surprised that rationalize (0.1)
does not equal 1/10. This behavior
isn't special to Maxima - the number 1/10 has a repeating, not a terminating,
binary representation.
(%i1) rationalize(0.5); (%o1) 1/2 (%i2) rationalize(0.1); (%o2) 3602879701896397/36028797018963968 (%i3) fpprec : 5$ (%i4) rationalize(0.1b0); (%o4) 209715/2097152 (%i5) fpprec : 20$ (%i6) rationalize(0.1b0); (%o6) 236118324143482260685/2361183241434822606848 (%i7) rationalize(sin(0.1 * x + 5.6)); (%o7) sin((3602879701896397*x)/36028797018963968+3152519739159347/562949953421312) |
Example use:
unitfrac(r) := block([uf : [], q], if not(ratnump(r)) then error("The input to 'unitfrac' must be a rational number"), while r # 0 do ( uf : cons(q : 1/ceiling(1/r), uf), r : r - q), reverse(uf)); (%i2) unitfrac(9/10); (%o2) [1/2,1/3,1/15] (%i3) apply("+",%); (%o3) 9/10 (%i4) unitfrac(-9/10); (%o4) [-1,1/10] (%i5) apply("+",%); (%o5) -9/10 (%i6) unitfrac(36/37); (%o6) [1/2,1/3,1/8,1/69,1/6808] (%i7) apply("+",%); (%o7) 36/37 |
Attempts to determine the sign of expr
on the basis of the facts in the current data base. It returns one of
the following answers: pos
(positive), neg
(negative), zero
, pz
(positive or zero), nz
(negative or zero), pn
(positive or negative),
or pnz
(positive, negative, or zero, i.e. nothing known).
For numeric x, returns 0 if x is 0, otherwise returns -1 or +1 as x is less than or greater than 0, respectively.
If x is not numeric then a simplified but equivalent form is returned.
For example, signum(-x)
gives -signum(x)
.
Sorts list according to a predicate p
of two arguments,
such as "<"
or orderlessp
.
sort (list)
sorts list according to Maxima's built-in ordering.
list may contain numeric or nonnumeric items, or both.
The square root of x. It is represented internally by
x^(1/2)
. See also rootscontract
.
radexpand
if true
will cause nth roots of factors of a product
which are powers of n to be pulled outside of the radical, e.g.
sqrt(16*x^2)
will become 4*x
only if radexpand
is true
.
Default value: true
When sqrtdispflag
is false
,
causes sqrt
to display with exponent 1/2.
Makes multiple parallel substitutions into an expression.
The variable sublis_apply_lambda
controls simplification after
sublis
.
Example:
(%i1) sublis ([a=b, b=a], sin(a) + cos(b)); (%o1) sin(b) + cos(a) |
Returns the list of elements of list for which the
predicate p
returns true
.
Example:
(%i1) L: [1, 2, 3, 4, 5, 6]$ (%i2) sublist (L, evenp); (%o2) [2, 4, 6] |
Default value: true
- controls whether lambda
's
substituted are applied in simplification after sublis
is used or
whether you have to do an ev
to get things to apply. true
means do the
application.
Substitutes a for b in c. b must be an atom or a
complete subexpression of c. For example, x+y+z
is a complete
subexpression of 2*(x+y+z)/w
while x+y
is not. When b does not have
these characteristics, one may sometimes use substpart
or ratsubst
(see below). Alternatively, if b is of the form e/f
then one could
use subst (a*f, e, c)
while if b is of the form e^(1/f)
then one could
use subst (a^f, e, c)
. The subst
command also discerns the x^y
in x^-y
so that subst (a, sqrt(x), 1/sqrt(x))
yields 1/a
. a and b may also be
operators of an expression enclosed in double-quotes "
or they may be function
names. If one wishes to substitute for the independent variable in
derivative forms then the at
function (see below) should be used.
subst
is an alias for substitute
.
subst (eq_1, expr)
or subst ([eq_1, ..., eq_k], expr)
are other permissible
forms. The eq_i are equations indicating substitutions to be made.
For each equation, the right side will be substituted for the left in
the expression expr.
exptsubst
if true
permits substitutions
like y
for %e^x
in %e^(a*x)
to take place.
When opsubst
is false
,
subst
will not attempt to substitute into the operator of an expression.
E.g. (opsubst: false, subst (x^2, r, r+r[0]))
will work.
Examples:
(%i1) subst (a, x+y, x + (x+y)^2 + y); 2 (%o1) y + x + a (%i2) subst (-%i, %i, a + b*%i); (%o2) a - %i b |
For further examples, do example (subst)
.
Similar to substpart
, but substinpart
works on the
internal representation of expr.
(%i1) x . 'diff (f(x), x, 2); 2 D (%o1) x . --- (f(x)) 2 dx (%i2) substinpart (d^2, %, 2); 2 (%o2) x . d (%i3) substinpart (f1, f[1](x+1), 0); (%o3) f1(x + 1) |
If the last argument to a part function is a list of indices then several subexpressions are picked out, each one corresponding to an index of the list. Thus
(%i1) part (x+y+z, [1, 3]); (%o1) z + x |
piece
holds the value of the last expression selected when using the
part functions. It is set during the execution of the function and
thus may be referred to in the function itself as shown below.
If partswitch
is set to true
then end
is returned when a
selected part of an expression doesn't exist, otherwise an error
message is given.
(%i1) expr: 27*y^3 + 54*x*y^2 + 36*x^2*y + y + 8*x^3 + x + 1; 3 2 2 3 (%o1) 27 y + 54 x y + 36 x y + y + 8 x + x + 1 (%i2) part (expr, 2, [1, 3]); 2 (%o2) 54 y (%i3) sqrt (piece/54); (%o3) abs(y) (%i4) substpart (factor (piece), expr, [1, 2, 3, 5]); 3 (%o4) (3 y + 2 x) + y + x + 1 (%i5) expr: 1/x + y/x - 1/z; 1 y 1 (%o5) - - + - + - z x x (%i6) substpart (xthru (piece), expr, [2, 3]); y + 1 1 (%o6) ----- - - x z |
Also, setting the option inflag
to true
and calling part
or substpart
is
the same as calling inpart
or substinpart
.
Substitutes x for the subexpression
picked out by the rest of the arguments as in part
. It returns the
new value of expr. x may be some operator to be substituted for an
operator of expr. In some cases x needs to be enclosed in double-quotes "
(e.g. substpart ("+", a*b, 0)
yields b + a
).
(%i1) 1/(x^2 + 2); 1 (%o1) ------ 2 x + 2 (%i2) substpart (3/2, %, 2, 1, 2); 1 (%o2) -------- 3/2 x + 2 (%i3) a*x + f (b, y); (%o3) a x + f(b, y) (%i4) substpart ("+", %, 1, 0); (%o4) x + f(b, y) + a |
Also, setting the option inflag
to true
and calling part
or substpart
is
the same as calling inpart
or substinpart
.
Returns true
if expr is a subscripted variable, for example
a[i]
.
Returns true
if expr is a symbol, else false
.
In effect, symbolp(x)
is equivalent to the predicate atom(x) and not numberp(x)
.
See also Identifiers
.
Disables the aliasing created by the last use of the ordering
commands ordergreat
and orderless
. ordergreat
and orderless
may not
be used more than one time each without calling unorder
.
See also ordergreat
and orderless
.
(%i1) unorder(); (%o1) [] (%i2) b*x + a^2; 2 (%o2) b x + a (%i3) ordergreat (a); (%o3) done (%i4) b*x + a^2; 2 (%o4) a + b x (%i5) %th(1) - %th(3); 2 2 (%o5) a - a (%i6) unorder(); (%o6) [a] |
Returns the vector potential of a given
curl vector, in the current coordinate system.
potentialzeroloc
has a similar role as for potential
, but the order of
the left-hand sides of the equations must be a cyclic permutation of
the coordinate variables.
Combines all terms of expr (which should be a sum) over a
common denominator without expanding products and exponentiated sums
as ratsimp
does. xthru
cancels common factors in the numerator and
denominator of rational expressions but only if the factors are
explicit.
Sometimes it is better to use xthru
before ratsimp
ing an
expression in order to cause explicit factors of the gcd of the
numerator and denominator to be canceled thus simplifying the
expression to be ratsimp
ed.
(%i1) ((x+2)^20 - 2*y)/(x+y)^20 + (x+y)^(-19) - x/(x+y)^20; 20 1 (x + 2) - 2 y x (%o1) --------- + --------------- - --------- 19 20 20 (y + x) (y + x) (y + x) (%i2) xthru (%); 20 (x + 2) - y (%o2) ------------- 20 (y + x) |
Tests whether the expression expr in the variable
v is equivalent to zero, returning true
, false
, or
dontknow
.
zeroequiv
has these restrictions:
For example zeroequiv (sin(2*x) - 2*sin(x)*cos(x), x)
returns
true
and zeroequiv (%e^x + x, x)
returns false
.
On the other hand zeroequiv (log(a*b) - log(a) - log(b), a)
returns dontknow
because
of the presence of an extra parameter b
.
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