> ## Documentation Index
> Fetch the complete documentation index at: https://errand.nuvrel.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# concat

> Combine two or more lists or tuples into a single sequence.

`concat(seqs...)` appends all given lists or tuples together and returns the combined result. If all inputs are lists of the same element type, the result is a list. Otherwise, the result is a tuple.

## Signature

```
concat(seqs... list | tuple) list | tuple
```

## Example

Combine a fixed set of required linting steps with an optional set of extra checks passed as a variable:

```hcl theme={null}
variable "extra_checks" {
  description = "Additional linting targets to include"
  type        = list(string)
  default     = []
}

computed "all_checks" {
  description = "Full set of linting targets"
  expression  = concat(["./internal/...", "./pkg/...", "./cmd/..."], var.extra_checks)
}

task "lint" {
  description = "Lint all packages"
  commands    = ["golangci-lint run ${join(" ", computed.all_checks)}"]
}
```

When `extra_checks` is empty, only the base packages are linted. When `--var 'extra_checks=["./tool/..."]'` is passed, the extra path is appended.

## Notes

* `concat` preserves order and duplicates. Use [`distinct`](/functions/collection/distinct) afterward if uniqueness is required.
* When mixing lists of different types or including tuples, the result is a tuple rather than a list.