NOTE

At some point in the future the Yapp-based parser will become the default! It is suggested you test your code against it before that. Code that uses the RecDescent based parser's "Extend" method may fail!

Until then, you need to load it by hand as follows:

  $Math::Symbolic::Parser = Math::Symbolic::Parser->new(
    implementation=>'Yapp'
  );

This replaces the default Math::Symbolic parser with an instance of the new Yapp parser.

STRING FORMAT

The supported builtin-functions are listed in the documentation for Math::Symbolic::Operator in the section on the new() constructor.

EXTENSIONS

EXAMPLES

  # An example from analytical mechanics:
  my $hamilton_function =
          Math::Symbolic->parse_from_string(
            'p_q(q, dq_dt, t) * dq_dt(q, t) - Lagrange(q, p_q, t)'
          );

This parses as "The product of the generalized impulse p_q (which is a function of the generalized coordinate q, its derivative, and the time) and the derivative of the generalized coordinate dq_dt (which depends on q itself and the time). This term minus the Lagrange Function (of q, the impulse, and the time) is the Hamilton Function."

Well, that's how it parses in my head anyway. The parser will generate a tree like this:

  Operator {
    type     => difference,
    operands => (
                  Operator {
                    type     => product,
                    operands => (
                                  Variable {
                                    name         => p_q,
                                    dependencies => q, dq_dt, t
                                  },
                                  Variable {
                                     name         => dq_dt,
                                     dependencies => q, t
                                  }
                    )
                  },
                  Variable {
                    name         => Lagrange,
                    dependencies => q, p_q, t
                  }
                )
  }

Possibly a simpler example would be 'amplitude * sin(phi(t))' which descibes an oscillation. sin(...) is assumed to be the sine function, amplitude is assumed to be a symbol / variable that doesn't depend on any others. phi is recognized as a variable that changes over time (t). So phi(t) is actually a function of t that hasn't yet been specified. phi(t) could look like 'omega*t + theta' where strictly speaking, omega, t, and theta are all symbols without dependencies. So omega and theta would be treated as constants if you derived them in respect to t. Figuratively speaking, omega would be a frequency and theta would be a initial value.

PARSING DERIVATIVES

With version 0.511, a new syntax for specifying partial derivatives was added to the parser(s). "f'(x)" denotes the first partial derivative of "f" with respect to "x". If "(x)" is omitted, "f'" defaults to using "x". "f''(a)" is the second order partial derivative with respect to "a". If there are multiple variables in the parenthesis, a la "f'(b, a)", the first variable is used for the derivatives.

EXPORT

Constructor new

The constructor takes key/value pairs of options.

You can regenerate the parser from the grammar in the scalar $Math::Symbolic::Parser::Grammar instead of using the (slightly faster) precompiled grammar from Math::Symbolic::Parser::Precompiled. You can enable recompilation from the grammar with the option "recompile => 1". This only has an effect if the implementation is the Parse::RecDescent based parser (which is the default).

If you care about parsing speed more than about being able to extend the parser at run-time, you can specify the "implementation" option. Currently recognized are "RecDescent" and "Yapp" implementations. "RecDescent" is the default and "Yapp" is significantly faster. The Parse::Yapp based implementation may not support all extension modules. It has been tested with Math::SymbolicX::ParserExtensionFactory and Math::SymbolicX::Complex.