Spreadsheet::Engine::Fn::base - base class for spreadsheet functions

  use base 'Spreadsheet::Engine::Fn::text';

This provides a base class for spreadsheet functions.

Each function will generally have an intermediate base class that extends this with methods specific to the type of function that it is providing.

Instantiates with the given variables.

As per SocialCalc (to document fully later)

Each function should declare how many arguments it expects. This should be 0 for no arguments, a positive integer for exactly that many arguments, or a negative integer for at least that many arguments (based on the absolute value).

In the latter case, an optional second value will declare a maximum number of arguments (e.g. return (-2, 4) = between 2 and 4 arguments)

If this method is not provided no checking of arguments is performed.

Functions may also declare a signature function that declares, for each operand that the function can receive, whether it must be 't' (text), 'n' (numeric), or in the case of a number, a test ('>0', '<=1') that it must pass. The entire operand stack can then be popped as $self->_ops, throwing an "Invalid arguments" error if required.

Functions should provide a result() method that will return a value/type hash containing the calculated response.

This will normally be calculated based on a lookup of the types of operands provided, but subclasses can override this.

This delegates to the response() method in the subclass, and pushes the response onto the stack.

	my $op = $self->next_operand
	print $op->{value} => $op->{type};

Pops the top of the operand stack and returns a hash containing the value and type. (This is currently a simple delegation to Sheet::operand_value_and_type/operand_as_text/operand_as_number

next_operand_as_text also encodes its return value as utf8.

Fetch the next operand using top_of_stack_value_and_type(). (This deals differently with ranges and co-ordinates.)

	my $type = $self->optype('twoargnumeric', $op1, $op2);

Returns the resulting value type when doing an operation.

This is a Modified Version of code extracted from SocialCalc::Functions in SocialCalc 1.1.0

Portions (c) Copyright 2005, 2006, 2007 Software Garden, Inc. All Rights Reserved.

Portions (c) Copyright 2007 Socialtext, Inc. All Rights Reserved.

Portions (c) Copyright 2007, 2008 Tony Bowden

The contents of this file are subject to the Artistic License 2.0; you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.perlfoundation.org/artistic_license_2_0