#Formulacrum

Formulacrum is an API for dynamically composing formulas for Microsoft Excel, without directly manipulating strings. It is intended for use in Excel add-ins or applications generating reports to be viewed in Excel.

###Requirements and Compatibility###

• Source is written in C#6, targeting .NET 4.0.
• Assembly is CLS compliant, for use with VB.NET, F#, etc. clients.
• Assembly is not yet COM visible, but this is a goal for use with VBA clients.
• The only dependencies are mscorlib.dll and System.dll. This (theoretically) allows for simple integration with any Excel automation or reporting API (ExcelDNA, PIA, VSTO, EPPlus, Aspose,...).

###Design###

• Formulacrum models an Excel formula as a tree-like hierarchy of objects called Nodes.
• Each Node represents a formula element, such as a function, operator, literal value, or reference.
• There is no "Formula" object at the top of the hierarchy, only nodes linked to nodes.
• Depending on the specific type, nodes can have zero or more child nodes. This nesting can go on repeatedly, much like in Excel. (Excel does have a formula length limit, and Formulacum does not, at least for now.)

###Benefits###

• Using an object model of formulas, rather than creating them with direct string manipulation, allows the client compiler to be used for some basic syntax checking on generated formulas.
• IDE text editor color schemes can be used to highlight the different syntactic parts of formulas, to give more readily visible structure.
• The code for generating formulas actually resembles the formulas themselves, as opposed to a low-level approach with StringBuilder and String.Format.
• Null slots can be left in the node hierarchy, for deferred binding of function or operator arguments.