latform

A Bmad lattice parser, formatter, and analysis toolkit for particle accelerator lattice files. It parses, formats, lints, diffs, inspects, and templates Bmad lattices, and also understands Tao tao.init / Fortran-namelist files.

Installation

pip install latform

conda env create -n latform python=3.12 pip
conda activate latform

git clone https://github.com/ken-lauer/latform
cd latform
python -m pip install .

Quickstart

# Format a lattice and print to stdout
latform my_lattice.bmad

# Format in place
latform -i my_lattice.bmad

# Preview what the formatter would change (no writes)
latform --diff my_lattice.bmad

# Format from a pipe
cat my_lattice.bmad | latform -

# Format every file in a directory, in place
latform -i *.bmad

# Lint without reformatting (exits non-zero on findings — good for CI)
latform-lint my_lattice.bmad

Point latform at a Tao tao.init and it formats the tao.init and every Bmad lattice it references:

latform -i tao.init        # rewrite the init and its lattices in place
latform --diff tao.init    # preview all of the changes

The tools

latform installs several focused commands:

Run any command with -h for its full option list, or see the CLI reference. A ninth command, latform-lsp, provides editor integration — see Editor integration.

Common operations

Enforce house style on save / in CI

See also: latform-pre-commit.

Format in place and lint as two steps:

latform -i lat/*.bmad         # reformat
latform-lint -r lat/main.bmad # lint recursively; exits 1 on any finding

Set your project's rules once in a latform.toml (see Configuration) so every invocation and every contributor gets the same result. latform --lint reports lints alongside the formatted output; latform-lint is the CI-friendly, exit-code-driven counterpart.

Rename elements

# Inline old,new pairs (repeatable)
latform -R 'Q1,QF' -R 'Q2,QD' my_lattice.bmad

# From a CSV of old,new pairs
latform --rename-file renames.csv my_lattice.bmad

Flatten a multi-file lattice into one

latform -r my_lattice.bmad         # parse recursively, following `call`s
latform --flatten my_lattice.bmad  # inline all called files into one output

Inspect a lattice

latform-dump my_lattice.bmad            # parameters, used, and unused elements
latform-dump -u my_lattice.bmad         # only unused elements
latform-dump -m 'Q*' my_lattice.bmad    # filter by glob (or -r for regex)
latform-dump -d ',' my_lattice.bmad     # CSV-style output

Compare lattices

latform-diff old.bmad new.bmad          # structural diff of params & elements
latform-gitdiff my_lattice.bmad HEAD~1  # compare a file against an earlier commit

Visualize the dependency tree

latform-graph my_lattice.bmad                 # text tree of `call`ed files
latform-graph -f mermaid -o deps.mmd main.bmad  # Mermaid diagram to a file

Fill in a single template file

A Bmad template is itself valid Bmad; --set edits one value inline, and a YAML sidecar supplies them in bulk.

latform-apply const.bmad --set 'A = 10' -i             # a constant
latform-apply quad.bmad --set 'Q1[k1] = 1.523'         # an element attribute
latform-apply quad.bmad --set 'parameter[e_tot] = 5e9' # a parameter
latform-apply quad.bmad --unset 'BEN0[type]'           # drop an attribute

# values.yaml:  Q1: { k1: 1.523 }
latform-apply quad.bmad --values values.yaml
latform-apply quad.bmad --rename 'Q(\d+)' 'ARC_Q\1'   # regex rename

The same command edits tao.init / namelist files, keyed by namelist group:

latform-apply tao.init --set 'tao_params[global%n_opti_cycles] = 50' -i

Expand a template set across instances

Describe the template files, per-instance values, and renames in an instances.yaml, then generate every instance at once:

latform-template instances.yaml -d build/            # write instances to build/
latform-template instances.yaml -d build/ --dry-run  # list files without writing

See Templating for the instances.yaml schema (prefix / suffix / regex / parts renames, shared context: files, and per-instance tao_init: generation).

Configuration

latform and latform-lint read project-wide settings from a latform.toml (bare tables) or a [tool.latform] section in pyproject.toml. Discovery walks upward from the current directory: the first latform.toml wins, otherwise the first pyproject.toml that contains a [tool.latform] table. --config PATH forces a specific file; --no-config skips config entirely.

Precedence is CLI flag → config → built-in default. Only latform and latform-lint read this file (latform-apply / latform-template take their namelist options as flags). The block below lists every recognized key with its default; unknown keys in [format] warn and are ignored.

# latform.toml — all options shown with their defaults.

# ── Entry points ────────────────────────────────────────────────────────────
# Used when latform / latform-lint run with NO file arguments. Paths are
# relative to this config file. Providing either implies recursive parsing.
top-level = ["lat/main.bmad"]     # list of lattice files
tao-init  = "tao.init"            # a path, or a list of paths; its
                                  # design_lattice files become the top level

# ── Formatting ──────────────────────────────────────────────────────────────
# Same names as the CLI flags, minus the leading `--`. An explicit CLI flag
# always overrides the value here.
[format]
line-length              = 100        # int
max-line-length          = 130        # int; default = 130% of line-length
compact                  = false      # bool; no blank lines between statement types
name-case                = "upper"    # upper | lower | same  (element names)
attribute-case           = "lower"    # upper | lower | same  (attribute names)
kind-case                = "lower"    # upper | lower | same  (element types/keywords)
builtin-case             = "lower"    # upper | lower | same  (builtin functions)
controller-variable-case = "same"     # upper | lower | same  (overlay/group/ramper vars)
section-break-character  = "-"        # str
section-break-width      = 100        # int; default = line-length
strip-comments           = false      # bool

# Namelist (tao.init / *.nml) formatting — also under [format]:
format-namelist          = true       # bool; false = preserve layout verbatim
namelist-indent          = 2          # int >= 0; field indent width
namelist-field-case      = "lower"    # upper | lower | same  (field names)
namelist-align-equals    = true       # bool; align `=` into a column
namelist-align-comments  = true       # bool; align trailing `!` comments
namelist-logicals        = ["T", "F"] # [true, false] tokens, or `false` to
                                      # leave logical values untouched

# ── Linting ─────────────────────────────────────────────────────────────────
[lint]
ignore                = ["LF002"]     # list of codes to suppress everywhere
min-name-length       = 1             # int >= 1; LF009 flags names shorter than this
                                      # (at 1, only the confusable i/l/o are flagged)
builtin-constant-rtol = 1e-4          # positive float; LF010 match tolerance vs.
                                      # built-in physical constants

# Per-file lint suppression. Keys are globs matched against the file's name,
# full path, and path relative to this config; values are codes to ignore there.
[lint.per-file-ignores]
"legacy/*.bmad"    = ["LF004", "LF006"]
"vendor/**/*.bmad" = ["LF004"]

Lint ignores are cumulative: --ignore on the CLI, the global [lint] ignore list, and any matching [lint.per-file-ignores] entries all apply.

The equivalent in pyproject.toml nests everything one level deeper under [tool.latform]:

[tool.latform]
top-level = ["lat/main.bmad"]

[tool.latform.format]
line-length = 100
name-case   = "upper"
kind-case   = "lower"

[tool.latform.lint]
ignore = ["LF002"]

[tool.latform.lint.per-file-ignores]
"legacy/*.bmad" = ["LF004", "LF006"]

With no config at all, the tools fall back to a tao.init found in the current directory or a parent, so they work in a bare Tao project directory. See the Lint Codes reference for what each LF0xx means.

Editor integration (language server)

latform ships a Language Server Protocol implementation, latform-lsp, for Bmad lattice files. It provides go-to-definition, find-references, hover, completion, rename, formatting (whole-file and range), document/workspace symbols, semantic highlighting, code actions, and live diagnostics from the same lint rules as latform-lint. It reads your project's latform.toml / pyproject.toml, so formatting and diagnostics match the CLI.

The server is behind the optional lsp extra (it needs pygls):

pip install "latform[lsp]"
latform-lsp --help        # runs over stdio; normally launched by your editor

Editor plugins

Ready-made clients that discover latform-lsp and wire up the Bmad filetype for you:

Each still needs latform-lsp on PATH (pip install "latform[lsp]"); see the plugin's README for install and configuration.

vim.filetype.add({
  extension = { bmad = "bmad", lat = "bmad" },
  filename = { ["tao.init"] = "bmad" },
})

vim.lsp.config("latform", {
  cmd = { "latform-lsp" },
  filetypes = { "bmad" },
  root_markers = { "latform.toml", "pyproject.toml", "tao.init", ".git" },
})
vim.lsp.enable("latform")

augroup latform_ft
  autocmd!
  autocmd BufRead,BufNewFile *.bmad,*.lat,tao.init setfiletype bmad
augroup END

if executable('latform-lsp')
  autocmd User lsp_setup call lsp#register_server({
    \ 'name': 'latform',
    \ 'cmd': {server_info->['latform-lsp']},
    \ 'allowlist': ['bmad'],
    \ })
endif

Using latform as a library

from latform import parse, parse_file, parse_file_recursive

result = parse_file("my_lattice.bmad")

See the Python API docs for details.

Documentation

• CLI reference — full usage for every command
• Configuration — latform.toml / pyproject.toml
• Style guide — the formatting rules latform applies
• Python API — using latform programmatically