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# STSHELL

STSHELL = “shell” - User-defined spectral transformation via callback functions for the application of the operator to a vector and (optionally) the backtransform operation.

## Note

In order to define a `shell` spectral transformation, the user has to provide the `apply` operation via `STShellSetApply()` and related functions, and optionally a `backtransform` operation via `STShellSetBackTransform()`, and in some cases a user-defined context containing relevant data via `STShellSetContext()`.

## See Also

ST: Spectral Transformation, `ST`, `STType`, `STSetType()`, `STShellSetApply()`, `STShellSetBackTransform()`, `STShellSetContext()`

## Level

beginner

## Location

src/sys/classes/st/impls/shell/shell.c

Index of all ST routines Table of Contents for all manual pages Index of all manual pages