which — Resolve which variable, builtin, file, or class matches a given name.
which name reports what RunMat will resolve for name according to MATLAB-compatible search precedence across variables, builtins, files, and class methods.
Syntax
result = which(name)
result = which(name, option)
result = which(option, name)
results = which("-all", name)Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
name | StringScalar | Yes | — | Name to resolve. |
option | StringScalar | No | "-all" | Optional mode filter (-all|-builtin|-var|-file). |
option | StringScalar | Yes | — | Mode filter (-all|-builtin|-var|-file). |
Returns
| Name | Type | Description |
|---|---|---|
result | StringScalar | Single resolution result string. |
results | Any | All matching resolution strings (cell array of char rows). |
Errors
| Identifier | When | Message |
|---|---|---|
| — | No input arguments are provided. | which: not enough input arguments |
| — | More than one name argument is provided. | which: too many input arguments |
| — | Name argument is not a char row or string scalar. | which: name must be a character vector or string scalar |
| — | Option argument is not a char row or string scalar. | which: option must be a character vector or string scalar |
| — | Conflicting mode options are combined. | which: conflicting option |
| — | An unrecognized mode option is provided. | which: unrecognized option |
How which works
- Names can be supplied as character vectors or string scalars. Calling
whichwith no name raiseswhich: not enough input arguments. which namewithout options returns the first match respecting MATLAB's precedence rules.which(name, "-all")(orwhich("-all", name)) returns a cell array with every match on the search path, in discovery order, without duplicates.which(..., "-builtin")restricts the search to builtin functions."-var"restricts to workspace variables, and"-file"restricts the search to files, classes, and folders.- Package-qualified names like
pkg.funcautomatically map to+pkgfolders. Class lookups recognise both@ClassNamefolders and.mfiles containingclassdef. - Relative paths are resolved against the current working directory. Absolute paths and paths beginning with
~or drive letters are honoured directly.
Does RunMat run which on the GPU?
which performs string parsing and filesystem inspection on the host CPU. If you pass GPU-resident strings (for example, gpuArray("sin")), RunMat gathers them automatically before evaluating the request. Results are always host-resident character arrays or cell arrays. Acceleration providers do not implement kernels for this builtin.
GPU memory and residency
No. which gathers GPU arguments implicitly and never produces device-resident output. There is no benefit in moving strings to the GPU before calling which.
Examples
Finding a built-in function's implementation
which("sin")Expected output:
built-in (RunMat builtin: sin)Checking if a workspace variable shadows a builtin
answer = 42;
which("answer")Expected output:
'answer' is a variable.Listing all matches on the path
which("sum", "-all")Expected output:
{
[1,1] = built-in (RunMat builtin: sum)
[2,1] = //runmat/stdlib/sum.m
}Locating a script or function file
which("helpers/process_data")Expected output:
//projects/runmat/helpers/process_data.mRestricting the search to variables
which("-var", "velocity")Expected output:
'velocity' is a variable.Restricting the search to files
which("fft", "-file")Expected output:
//runmat/overrides/fft.mUsing which with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how which changes the result.
Run a small which example, explain the result, then change one input and compare the output.
FAQ
What happens when nothing is found?⌄
which returns the character vector '<name>' not found. just like MATLAB.
Are method lookups supported?⌄
Methods defined via @Class folders or classdef files are discovered through the class search. Package-qualified methods are supported.
Does which canonicalise paths?⌄
Yes. RunMat reports canonical absolute paths where possible; when canonicalisation fails, the original path is returned.
Can I combine -all with other options?⌄
Yes. For example, which("plot", "-all", "-file") lists every file-based implementation without reporting builtins or variables.
Does the search respect RUNMAT_PATH / MATLABPATH?⌄
Yes. The directory list mirrors the logic used by other REPL filesystem builtins.
What about Simulink models or Java classes?⌄
File-based matches with supported extensions (.slx, .mdl, .class, etc.) are reported when present on the path.
Are duplicate results filtered?⌄
Yes. The first occurrence of each unique path is returned.
Is the lookup case sensitive?⌄
No. Matching is case-insensitive on all platforms, following MATLAB semantics.
Does which gather GPU values?⌄
Yes. GPU-resident arguments are automatically gathered before the search begins.
Related Introspection functions
addprop · assignin · class · clear · clearAllMemoizedCaches · clearCache · clearvars · dbclear · dbstack · dbstatus · dbtype · evalc · feval · findprop · getcallinfo · inputParser · isa · ischar · isdeployed · iskeyword · ismethod · isobject · isstring · isUnderlyingType · keyboard · matlab.metadata.DynamicProperty.delete · memoize · metaclass · mislocked · mlock · munlock · namelengthmax · narginchk · nargoutchk · notify · onCleanup · stats · str2func · superclasses · underlyingType · verLessThan · version · who · whos
Open-source implementation
Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how which is executed, line by line, in Rust.
- View the source for which in Rust on GitHub
- Learn how the RunMat runtime works
- Found a bug? Open an issue with a minimal reproduction.
About RunMat
RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.
- RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
- Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.