Math::NumSeq::Expression -- mathematical expression values
use Math::NumSeq::Expression; my $seq = Math::NumSeq::Expression->new (expression => '2*i+1'); my ($i, $value) = $seq->next;
A string expression evaluated at i=0, 1, 2, etc, by Perl or a choice of evaluator modules.
This is designed to take expression strings from user input though could be used for something quick from program code too.
The default expression_evaluator => 'Perl'
evaluates with Perl itself. This is always available. Expressions are run with the Safe
module to restrict to arithmetic (see Safe).
The i index is in a $i
variable and an i()
function. The i()
function is prototyped like a constant.
i+1 2*$i - 2
The functions made available include
atan2 sin cos exp log \ Perl builtins sqrt rand / min max List::Util floor ceil POSIX module cbrt hypot erf erfc expm1 \ j0 j1 jn lgamma_r log10 | Math::Libm log1p pow rint y0 y1 yn / tan asin acos atan \ csc cosec sec cot cotan | Math::Trig acsc acosec asec acot acotan | sinh cosh tanh | csch cosech sech coth cotanh | asinh acosh atanh | acsch acosech asech acoth acotanh /
expression_evaluator => 'MS'
selects the Math::Symbolic
module, if available.
The expression is parsed with Math::Symbolic->parse_from_string()
and should use a single variable for the i index in the sequence. The variable can be any name, not just "i"
2*i+1 x^2 + x + 1 # any single variable
The usual $ms->simplify()
is applied to perhaps reduce the expression a bit, then to_sub()
for actual evaluation.
expression_evaluator => 'MEE'
selects the Math::Expression::Evaluator
module, if available.
The expression should use a single input variable, which can be any name, and takes the i index in the sequence. Temporary variables can be used by assigning to them,
x^2 + x + 1 # any single variable t=2*i; t^2 # temporary variables assigned
The expression is run with $mee->compiled()
. It turns the expression into a Perl subr for actual evaluation.
expression_evaluator => 'LE'
selects the Language::Expr
module, if available.
The expression should use a single variable, of any name, which will be the i index in the sequence. See Language::Expr::Manual::Syntax for the expression syntax.
$x*$x + $x + 1
The expression is compiled with Language::Expr::Compiler::Perl for evaluation.
See "FUNCTIONS" in Math::NumSeq for behaviour common to all sequence classes.
$seq = Math::NumSeq::Expression->new (radix => $r, modulus => $d)
Create and return a new sequence object.
$value = $seq->ith($i)
Return the expression
evaluated at $i
.
Safe.pm
seems a bit of a slowdown. Is that right or is it supposed to validate ops during the eval which compiles a subr?
http://user42.tuxfamily.org/math-numseq/index.html
Copyright 2010, 2011, 2012, 2013, 2014 Kevin Ryde
Math-NumSeq is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.
Math-NumSeq is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with Math-NumSeq. If not, see <http://www.gnu.org/licenses/>.