# LibTmux.FSharp.Filter.eq

- **Module:** LibTmux.FSharp
- **Package:** LibTmux.FSharp
- **Language:** F#
- **Kind:** function
- **Source:** https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/src/LibTmux.FSharp/Query.fsi#L33
- **Page:** https://libtmux.org/en/fsharp/latest/reference/libtmux-fsharp-filter-eq/

```
val eq: value: 'Value -> field: Field<'T, 'Value> -> Filter<'T>
```

Matches a field equal to a constant.

## Examples

Compare native sequence filtering with portable F# filters. Capture the hierarchy before following pane and window relations; listing alone does not capture children. Use Linux or macOS with Git, tmux 3.2a or newer, .NET SDK 10.0.303, and the .NET 8 and 10 runtimes. In an empty directory, fetch the documented library revision:

```console
$ git clone https://github.com/libtmux/libtmux-dotnet.git libtmux-source && \
  git -C libtmux-source checkout --detach cf34b255c896d19a97e7d7fabea58609c916012d
```

Save this complete consumer setup as global.json:

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/global.json).

```json
{
  "sdk": {
    "version": "10.0.303",
    "rollForward": "disable",
    "allowPrerelease": false
  },
  "test": {
    "runner": "Microsoft.Testing.Platform"
  }
}
```

Save this complete consumer setup as NuGet.config:

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/examples/api/NuGet.config).

```xml
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <clear />
    <add key="libtmux-source" value="libtmux-source/artifacts/api-example-packages" />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
  <packageSourceMapping>
    <clear />
    <packageSource key="libtmux-source">
      <package pattern="LibTmux" />
      <package pattern="LibTmux.*" />
    </packageSource>
    <packageSource key="nuget.org">
      <package pattern="*" />
    </packageSource>
  </packageSourceMapping>
</configuration>
```

Save this complete consumer setup as Example.fsproj:

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/examples/api/fsharp/Example.fsproj).

```xml
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFrameworks>net8.0;net10.0</TargetFrameworks>
    <LangVersion>10.0</LangVersion>
    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
    <DisableImplicitFSharpCoreReference>true</DisableImplicitFSharpCoreReference>
    <DisableImplicitLibraryPacksFolder>true</DisableImplicitLibraryPacksFolder>
  </PropertyGroup>
  <ItemGroup>
    <Compile Include="Program.fs" />
    <PackageReference Include="FSharp.Core" Version="[10.1.303]" />
    <PackageReference Include="LibTmux.FSharp" Version="[0.0.0-alpha.20]" />
  </ItemGroup>
</Project>
```

Save this complete program as Program.fs. It creates a private server with LibTmux.Server.CreateOwnedAsync; use! disposes owned scopes after success, cancellation or failure. The F# facade has no separate server constructor.

[Source example](https://github.com/libtmux/libtmux-dotnet/blob/cf34b255c896d19a97e7d7fabea58609c916012d/examples/LibTmux.FSharp.Examples/Programs/ServerFilters.fs).

```fsharp
// fsharp-snippet: ServerFilters
open System
open System.Threading
open LibTmux
open LibTmux.FSharp

let runAsync () =
    task {
        use deadline = new CancellationTokenSource(TimeSpan.FromSeconds 10.)
        let token = deadline.Token

        let options =
            ServerConnectionOptions(
                SocketName = "fsharp-filters-" + Guid.NewGuid().ToString("N"),
                ConfigurationFile = "/dev/null"
            )

        use! owned = options |> Server.createOwned token

        use! demo =
            owned.Value.CreateOwnedSessionAsync(
                NewSessionRequest(Name = "demo", WindowName = "shell", Command = "/bin/sh"),
                token
            )

        use! _worker =
            owned.Value.CreateOwnedSessionAsync(
                NewSessionRequest(Name = "worker", WindowName = "jobs", Command = "/bin/sh"),
                token
            )

        let server = owned.Value
        let! sessions = server |> Server.sessions |> Query.list token

        let nativeMatches =
            sessions
            |> Seq.filter (fun session -> session.Name.StartsWith("de", StringComparison.Ordinal))
            |> Seq.toList

        let portableMatches =
            sessions |> Query.matching (Filter.startsWith "de" SessionFields.name)

        let! windows = server |> Server.windows |> Query.list token

        let matchingWindows =
            windows |> Query.matching (Filter.eq "shell" WindowFields.name)

        let! captured = server |> Server.capture token SnapshotDepth.Panes

        let demoSession =
            captured.Sessions |> Seq.find (fun session -> session.Id = demo.Value.Id)

        let demoPane =
            demoSession.Windows
            |> Seq.collect (fun window -> window.Panes)
            |> Seq.exactlyOne

        let paneFilter = Filter.eq demoPane.Id PaneFields.id
        let matchingPanes = captured.Panes |> Query.matching paneFilter

        let hasDemoPane =
            paneFilter |> Filter.any WindowFields.panes |> Filter.any SessionFields.windows

        let matchingParents = captured.Sessions |> Query.matching hasDemoPane

        use! _control = server |> Control.enter token
        let! clients = server |> Server.clients |> Query.list token

        let controlClients =
            clients |> Query.matching (Filter.eq true ClientFields.controlMode)

        let names (sessions: seq<LibTmux.Session>) =
            [ for session in sessions -> session.Name ]

        printfn "native: %A" (names nativeMatches)
        printfn "portable: %A" (names portableMatches)
        printfn "windows: %A" [ for window in matchingWindows -> window.Name ]
        printfn "panes: %d" matchingPanes.Count
        printfn "parents: %A" (names matchingParents)
        printfn "control clients: %d" controlClients.Count
    }

runAsync().GetAwaiter().GetResult()
// endfsharp-snippet
```

Build the exact source packages and the saved consumer, then run both supported frameworks. The local package feed prevents an unrelated published package from satisfying the restore. Each program checks its result and exits unsuccessfully after an unhandled error:

```console
$ export NUGET_PACKAGES="$PWD/packages" && \
  dotnet restore libtmux-source/src/LibTmux.FSharp/LibTmux.FSharp.fsproj --locked-mode && \
  dotnet pack libtmux-source/src/LibTmux/LibTmux.csproj \
    --configuration Release --no-restore -p:ContinuousIntegrationBuild=true \
    --output "$PWD/libtmux-source/artifacts/api-example-packages" && \
  dotnet pack libtmux-source/src/LibTmux.FSharp/LibTmux.FSharp.fsproj \
    --configuration Release --no-restore -p:ContinuousIntegrationBuild=true \
    --output "$PWD/libtmux-source/artifacts/api-example-packages" && \
  dotnet restore Example.fsproj --configfile NuGet.config && \
  dotnet build Example.fsproj --configuration Release --no-restore --warnaserror && \
  export LIBTMUX_TMUX="$(command -v tmux)" && \
  export TMUX_TMPDIR=/tmp/libtmux-dotnet-dev && \
  mkdir -p "$TMUX_TMPDIR" && \
  unset TMUX TMUX_PANE && \
  dotnet bin/Release/net8.0/Example.dll && \
  dotnet bin/Release/net10.0/Example.dll
```

Expected program output from each framework:

```text
native: ["demo"]
portable: ["demo"]
windows: ["shell"]
panes: 1
parents: ["demo"]
control clients: 1
```

## Parameters

- `value` (`'Value`)
- `field` (`Field<'T, 'Value>`)