1Math::Symbolic::CompileUrs(e3r)Contributed Perl DocumentMaattiho:n:Symbolic::Compiler(3)
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6 Math::Symbolic::Compiler - Compile Math::Symbolic trees to Perl code
7
9 use Math::Symbolic::Compiler;
10 # A tree to compile
12 my $tree = Math::Symbolic->parse_from_string('a^2 + b * c * 2');
13 # The Math::Symbolic::Variable 'a' will be evaluated to $_[1], etc.
15 my $vars = [qw(b a c)];
16 my ($closure, $code, $trees) =
18 Math::Symbolic::Compiler->compile($tree, $vars);
19 print $closure->(2, 3, 5); # (b, a, c)
21 # prints 29 (= 3^2 + 2 * 5 * 2)
22 # or:
24 ($closure, $trees) =
25 Math::Symbolic::Compiler->compile_to_sub($tree, $vars);
26 ($code, $trees) = Math::Symbolic::Compiler->compile_to_code($tree, $vars);
28
30 This module allows one to compile Math::Symbolic trees to Perl code
31 and/or anonymous subroutines whose arguments will be positionally
32 mapped to the variables of the compiled Math::Symbolic tree.
33 The reason you'd want to do this is that evaluating a Math::Symbolic
35 tree to its numeric value is extremely slow. So is compiling, but once
36 you've done all necessary symbolic calculations, you can take advantage
37 of the speed gain of invoking a closure instead of evaluating a tree.
38 UNCOMPILED LEFTOVER TREES
40 Not all, however, is well in the land of compiled Math::Symbolic trees.
41 There may occasionally be trees that cannot be compiled (such as a
42 derivative) which need to be included into the code as trees. These
43 trees will be returned in a referenced array by the compile*() methods.
44 The closures will have access to the required trees as a special
45 variable '@_TREES inside the closure's scope, so you need not worry
46 about them in that case. But if you plan to use the generated code
47 itself, you need to supply an array named @_TREES that contains the
48 trees as returned by the compile*() methods in the scope of the eval()
49 you evaluate the code with.
50 Note that you give away all performance benefits compiling the tree
52 might have if the closure contains uncompiled trees. You can tell there
53 are any by checking the length of the referenced array that contains
54 the trees. If it's 0, then there are no trees left to worry about.
55 AVOIDING LEFTOVER TREES
57 In most cases, this is pretty simple. Just apply all derivatives in the
58 tree to make sure that there are none left in the tree. As of version
59 0.130, there is no operator except derivatives that cannot be compiled.
60 There may, however, be some operators you cannot get rid of this easily
61 some time in the future. If you have problems getting a tree to
62 compile, try using the means of simplification provided by
63 Math::Symbolic::* to get a simpler tree for compilation.
64 EXPORT
66 None by default, but you may choose to import the compile(),
67 compile_to_sub(), and compile_to_code() subroutines to your namespace
68 using the standard Exporter semantics including the ':all' tag.
69
71 ($code, $trees) = compile_to_code($tree, $vars)
72 The compile_to_code() class method takes one mandatory argument which
73 is the Math::Symbolic tree to be compiled. Second argument is optional
74 and an array reference to an array of variable mappings. See "VARIABLE
75 PASSING STYLES" for details on how this works.
76 compile_to_code() returns a string and an array reference. The string
78 contains the compiled Perl code that uses the values stored in @_ as
79 described in the section on positional variable passing. It also
80 accesses a special variable @_TREES if there were any sub-trees (inside
81 the tree that has been compiled) that were impossible to compile. The
82 array reference returned by this method contains any of the
83 aforementioned trees that failed to compile.
84 If there are any such trees that did not compile, you may put them into
86 the @_TREES variable in scope of the eval() that evaluates the compiled
87 code in the same order that they were returned by this method. If you
88 do that, the code will run and determine the value of the tree at run-
89 time. Needless to say, that is slow.
90 ($sub, $trees) = compile_to_sub($tree, $vars)
92 The compile_to_sub() class method takes one mandatory argument which is
93 the Math::Symbolic tree to be compiled. Second argument is optional and
94 an array reference to an array of variable mappings. See "VARIABLE
95 PASSING STYLES" for details on how this works.
96 compile_to_sub() returns a list of two elements, the first being the
98 compiled anonymous subroutine. For details on the second element,
99 please refer to the docs on the compile_to_code() subroutine.
100 ($sub, $code, $trees) = compile($tree, $vars)
102 The compile() class method takes one mandatory argument which is the
103 Math::Symbolic tree to be compiled. Second argument is optional and an
104 array reference to an array of variable mappings. See "POSITIONAL
105 VARIABLE PASSING" for details on how this works.
106 compile() returns a list of three elements, the first being the
108 compiled anonymous subroutine, the second being the compiled code. For
109 details on the second and third elements, please refer to the docs on
110 the compile_to_code() subroutine.
111 VARIABLE PASSING STYLES
113 Currently, the Math::Symbolic compiler only supports compiling to subs
114 with positional variable passing. At some point, the user should be
115 able to choose between positional- and named variable passing styles.
116 The difference is best explained by an example:
117 # positional:
119 $sub->(4, 5, 1);
120 # named: (NOT IMPLEMENTED!)
122 $sub->(a => 5, b => 4, x => 1);
123 With positional variable passing, the subroutine statically maps its
125 arguments to its internal variables. The way the subroutine does that
126 has been fixed at compile-time. It is determined by the second argument
127 to the various compile_* functions found in this package. This second
128 argument is expected to be a reference to an array of variable names.
129 The order of the variable names determines which parameter of the
130 compiled sub will be assigned to the variable. Example:
131 my ($sub) =
133 Math::Symbolic::Compiler->compile_to_sub($tree, [qw/c a b/]);
134 # First argument will be mapped to c, second to a, and third to b
136 # All others will be ignored.
137 $sub->(4, 5, 6, 7);
138 # Variable mapping: a = 5, b = 6, c = 4
140 One important note remains: if any (or all) variables in the tree are
142 unaccounted for, they will be lexicographically sorted and appended to
143 the variable mapping in that order. That means if you don't map
144 variables yourself, they will be sorted lexicographically.
145 Thanks to Henrik Edlund's input, it's possible to pass a hash reference
147 as second argument to the compile* functions instead of an array
148 reference. The order of the mapped variables is then determined by
149 their associated value, which should be an integer starting with 0.
150 Example:
151 Math::Symbolic::Compiler->compile_to_sub($tree, {b => 2, a => 1, c => 0});
153 Would result in the order c, a, b.
155
157 Please send feedback, bug reports, and support requests to the
158 Math::Symbolic support mailing list: math-symbolic-support at lists dot
159 sourceforge dot net. Please consider letting us know how you use
160 Math::Symbolic. Thank you.
161 If you're interested in helping with the development or extending the
163 module's functionality, please contact the developers' mailing list:
164 math-symbolic-develop at lists dot sourceforge dot net.
165 List of contributors:
167 Steffen Mueller, symbolic-module at steffen-mueller dot net
169 Stray Toaster, mwk at users dot sourceforge dot net
170 Oliver Ebenhoeh
171
173 New versions of this module can be found on http://steffen-mueller.net
174 or CPAN. The module development takes place on Sourceforge at
175 http://sourceforge.net/projects/math-symbolic/
176 Math::Symbolic
178perl v5.30.0 2019-07-26 Math::Symbolic::Compiler(3)