Elm-Spreadsheet

Elm-spreadsheet provides the means to represent and compute with spreadsheets. A spreadsheet is a two-dimensional array of cells, each of which may contain either data (values) or formulas. To evaluate a spreadsheet is to apply the formulas to create a new spreadsheet. If the new spreadsheet contains no formulas, we say that it is fully evaluated. The eval function calls itself repeatedly so as to attempt full evaluation.

Representation

A Spreadsheet is defined internally as an Array2D Cell. Externally, it can be represented as a string, with cells separated by semicolons. Cells are referred to in the same way as in Excel.

ss = """
100; 1.1; mul A1,A2
120; 1.4; mul B1,B2
140; 0.8; mul C1,C2
-;   add A2:C2; add A3:C3
"""

The entry mul A1,A2 means multiply the contents of cell A1 by the contents of cell A2. The entry add A2:C2 means add the entries in column 2 between rows A and C.

Use

   read: String -> Spreadsheet

to compute the internal representation as Array2D Cell, use

   eval : Spreadsheet -> Spreadsheet

to evaluate the formulas in a spreadsheet, and use

  print : Spreadsheet -> String

to render the result back into text:

   > ss |> read |>  eval |> print
  "100; 1.1; 110\n120; 1.4; 168\n140; 0.9; 126\n-; 3.4; 404"

Thus the result is the fully evaluated spreadsheet

100; 1.1; 110
120; 1.4; 168
140; 0.9; 126
-;   3.4; 404

Operations

Currently the operations implemented are limited:

add A1,H4   -- cellwise addition
mul A1,H4   -- cellwise multiplication
sub A1,H4   -- cellwise subtraction
div A1,H4   -- cellwise division


add B2:B9   -- add the elements of row B from columns 2 through 9
add B2:Q2   -- add the elements of column 2 from rows B through Q

More operations later.