[gdal-dev] gdal raster calc - a modulo operator (%)?

[Daniel Baston]

It's fairly straightforward to define functions in C++ and register them
with muparser. You can see how we do this with "isnan" and "isnodata" here:

https://github.com/OSGeo/gdal/blob/ca7a2d38893a8d6cdc03653b47712f4442d99d65/frmts/vrt/vrtexpression_muparser.cpp#L27

I don't think we want too many custom functions, but adding "mod" seems
like a good idea.

Dan

On Tue, Oct 7, 2025 at 12:30 PM Scott via gdal-dev <gdal-dev at lists.osgeo.org>
wrote:

> Greetings!
>
> I've been unable to find a modulo operator in CLI calc. It's not in the
> muparser functions or appear to be in the forth-coming 3.12 C pixel
> functions.
>
> This has been working with muparser, but it's messy every time you need
> a simple modulo. pixel is real or int, div is int:
>
> rint(pixel) - (rint(rint(pixel) / div) * div)
>
> Am I missing something? If not, consider this a feature request! :)
>
> Thanks!
> Scott
>
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