1Math::NumSeq::ExpressioUns(e3r)Contributed Perl DocumentMaattiho:n:NumSeq::Expression(3)
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6 Math::NumSeq::Expression -- mathematical expression values
7
9 use Math::NumSeq::Expression;
10 my $seq = Math::NumSeq::Expression->new (expression => '2*i+1');
11 my ($i, $value) = $seq->next;
12
14 A string expression evaluated at i=0, 1, 2, etc, by Perl or a choice of
15 evaluator modules.
16 This is designed to take expression strings from user input though
18 could be used for something quick from program code too. The
19 expression syntax in the evaluator modules varies in subtle ways.
20 Perl
22 The default "expression_evaluator => 'Perl'" evaluates with Perl
23 itself. This is always available. Expressions are run with the "Safe"
24 module to restrict to arithmetic (see Safe).
25 The i index is in a $i variable and an i() function. The i() function
27 is prototyped like a constant.
28 i+1
30 2*$i - 2
31 The functions made available include
33 atan2 sin cos exp log \ Perl builtins
35 sqrt rand /
36 min max List::Util
37 floor ceil POSIX module
38 cbrt hypot erf erfc expm1 \
39 j0 j1 jn lgamma_r log10 | Math::Libm
40 log1p pow rint y0 y1 yn /
41 tan asin acos atan \
42 csc cosec sec cot cotan | Math::Trig
43 acsc acosec asec acot acotan |
44 sinh cosh tanh |
45 csch cosech sech coth cotanh |
46 asinh acosh atanh |
47 acsch acosech asech acoth acotanh /
48 Math-Symbolic
50 "expression_evaluator => 'MS'" selects the "Math::Symbolic" module, if
51 available.
52 The expression is parsed with "Math::Symbolic->parse_from_string()" and
54 should use a single variable for the i index in the sequence. The
55 variable can be any name, not just "i"
56 2*i+1
58 x^2 + x + 1 # any single variable
59 The usual "$ms->simplify()" is applied to perhaps reduce the expression
61 a bit, then to_sub() for actual evaluation.
62 Math-Expression-Evaluator
64 "expression_evaluator => 'MEE'" selects the
65 "Math::Expression::Evaluator" module, if available.
66 The expression should use a single input variable, which can be any
68 name, and takes the i index in the sequence. Temporary variables can
69 be used by assigning to them,
70 x^2 + x + 1 # any single variable
72 t=2*i; t^2 # temporary variables assigned
73 The expression is run with "$mee->compiled()". It turns the expression
75 into a Perl subr for actual evaluation.
76 Language-Expr
78 "expression_evaluator => 'LE'" selects the "Language::Expr" module, if
79 available.
80 The expression should use a single variable, of any name, which will be
82 the i index in the sequence. See Language::Expr::Manual::Syntax for
83 the expression syntax.
84 $x*$x + $x + 1
86 The expression is compiled with Language::Expr::Compiler::perl for
88 evaluation.
89
91 See "FUNCTIONS" in Math::NumSeq for behaviour common to all sequence
92 classes.
93 "$seq = Math::NumSeq::Expression->new (expression => $str)"
95 Create and return a new sequence object.
96 Random Access
98 "$value = $seq->ith($i)"
99 Return the "expression" evaluated at $i.
100
102 "Safe.pm" seems a bit of a slowdown. Is that right or is it supposed
103 to validate ops during the eval which compiles a subr?
104
106 Math::NumSeq, Safe Math::Symbolic, Math::Expression::Evaluator,
107 Language::Expr
108
110 <http://user42.tuxfamily.org/math-numseq/index.html>
111
113 Copyright 2010, 2011, 2012, 2013, 2014, 2016, 2019, 2020 Kevin Ryde
114 Math-NumSeq is free software; you can redistribute it and/or modify it
116 under the terms of the GNU General Public License as published by the
117 Free Software Foundation; either version 3, or (at your option) any
118 later version.
119 Math-NumSeq is distributed in the hope that it will be useful, but
121 WITHOUT ANY WARRANTY; without even the implied warranty of
122 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
123 General Public License for more details.
124 You should have received a copy of the GNU General Public License along
126 with Math-NumSeq. If not, see <http://www.gnu.org/licenses/>.
127perl v5.36.0 2023-01-20 Math::NumSeq::Expression(3)