excel-d 0.2.6

Excel bindings for D

To use this package, put the following dependency into your project's dependencies section:



Excel API bindings and wrapper API for D

This dub package contains D declarations for the Excel SDK as well as a D wrapper API. This allows programmers to write Excel worksheet functions in D.

Motivation and background for the project can be found here. And you can see the lightning talk by Atila Neves.

Generated documentation - a work in progress - is available at Kaleidic Open Source Documentation for Excel-D.

A working XLL example can be found in the example directory. Running dub build there will create an XLL (myxll32.xll) that can be loaded in Excel making all of the functions in test/xlld/test_d_funcs.d available to be used in Excel cells. The types are automatically converted between D native types and Excel ones. To build the example: dub build -c example [--arch=x86_mscoff|--arch=x86_64].

For this package to build you will need the Excel SDK xlcall32.lib that can be downloaded from Microsoft. Copying it to the build directory should be sufficient (i.e. when building the example, to the example directory). The library file should be useable as-is, as long as on 32-bit Excel dub build is run with --arch=x86_mscoff to use Microsoft's binary format. If linking with optlink, the file must be converted first. We recommend using link.exe to not need the conversion. On 64 bit Excel just use --arch=x86_64 - no questions of different library formats.

Excel won't load the XLL automatically: this must be done manually in File->Tools->Add-Ins. Click on "Go" for "Excel Add-Ins" (the default) and select your XLL there after clicking on "Browse".

The only difference between building for 32-bit or 64-bit Excel is the arch= option passed to dub. A 32-bit XLL will only work on 32-bit Excel and similarly for 64-bit. You will also need the appropriate 32/64 xlcall32.lib from the Excel SDK to link.

Sample code (see the example directory for more):

    import xlld;

    @Register(ArgumentText("Array to add"),
              HelpTopic("Adds all cells in an array"),
              FunctionHelp("Adds all cells in an array"),
              ArgumentHelp(["The array to add"]))
    double FuncAddEverything(double[][] args) nothrow @nogc { // must be nothrow, @nogc optional
        import std.algorithm: fold;
        import std.math: isNaN;

        double ret = 0;
        foreach(row; args)
            ret += row.fold!((a, b) => b.isNaN ? 0.0 : a + b)(0.0);
        return ret;

and then in Excel:


Future functionality will include creating menu items and dialogue boxes. Pull requests welcomed.

Optional custom memory allocation and @nogc

If you are not familiar with questions of memory allocation, the below may seem intimidating. However it's entirely optional and unless performance and latency are critical to you (or possibly if you are interfacing with C or C++ code) then you do not need to worry about the extra complexity introduced by using allocators. The code in the previous section will simply work.

excel-d uses a custom allocator for all allocations that are needed when doing the conversions between D and Excel types. It uses a different one for allocations of XLOPER12s that are returned to Excel, which are then freed in xlAutoFree12 with the same allocator. D functions that are @nogc are wrapped by @nogc Excel functions and similarly for @safe. However, if returning a value that is dynamically allocated from a D function and not using the GC (such as an array of doubles), it is necessary to specify how that memory is to be freed. An example:

// @Dispose is used to tell the framework how to free memory that is dynamically
// allocated by the D function. After returning, the value is converted to an
// Excel type and the D value is freed using the lambda defined here.
@Dispose!((ret) {
    import std.experimental.allocator.mallocator: Mallocator;
    import std.experimental.allocator: dispose;
double[] FuncReturnArrayNoGc(double[] numbers) @nogc @safe nothrow {
    import std.experimental.allocator.mallocator: Mallocator;
    import std.experimental.allocator: makeArray;
    import std.algorithm: map;

    try {
        // Allocate memory here in order to return an array of doubles.
        // The memory will be freed after the call by calling the
        // function in `@Dispose` above
        return Mallocator.instance.makeArray(numbers.map!(a => a * 2));
    } catch(Exception _) {
        return [];

This allows for @nogc functions to be called from Excel without memory leaks.

Registering code to run when the XLL is unloaded

Since this library automatically writes xlAutoClose it is not possible to use it to run custom code at XLL unloading. As an alternative XLL writers can use xlld.xll.registerAutoCloseFunc passing it a function or a delegate to be executed when xlAutoClose is called.

About Kaleidic Associates

We are a boutique consultancy that advises a small number of hedge fund clients. We are not accepting new clients currently, but if you are interested in working either remotely or locally in London or Hong Kong, and if you are a talented hacker with a moral compass who aspires to excellence then feel free to drop me a line: laeeth at kaleidic.io

We work with our partner Symmetry Investments, and some background on the firm can be found here:


Authors:Laeeth Isharc, Stefan Koch, Atila Neves


0.2.6 2017-Jul-04
0.2.5 2017-Jun-26
0.2.4 2017-May-03
0.2.3 2017-Apr-28
0.2.2 2017-Apr-27
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