ENDF Syntax Highlighting

Syntax highlighting for ENDF and ENDF-6 evaluated nuclear data files in VS Code.

This extension helps inspect fixed-width ENDF records by contributing a language id, a TextMate grammar, and a small runtime hover provider. It is intentionally lightweight: there is no parser, diagnostics engine, language server, or network dependency.

Supported Files

VS Code recognizes these extensions as ENDF by default:

• .endf
• .endf6
• .pendf
• .gendf
• .tape

It also recognizes ENDF-like .dat files through ENDF-specific filename patterns such as *endf*.dat, *pendf*.dat, and *gendf*.dat. Generic .dat files are not claimed by extension alone; files with no specific extension can still be detected when the first line has an ENDF-like fixed-column tail.

Highlighting Model

ENDF records are fixed-width cards. The grammar treats each line as:

• columns 1-66: payload fields
• columns 67-70: MAT
• columns 71-72: MF
• columns 73-75: MT
• columns 76-80: optional sequence number (NS)

Both 75-column records, where the sequence number is omitted, and standard 80-column records are supported.

The grammar highlights:

• fixed-width numeric payload fields, including ENDF implicit-exponent values such as 3.007000+3
• integer control fields
• MAT, MF, MT, and optional NS tail columns
• SEND, FEND, MEND, and TEND structural end records
• MF ..., MT ..., MF=..., and MT=... references in descriptive text

Number Meanings

When the cursor, selection, or hover is on a recognized ENDF number, the extension explains the fixed-column meaning. Selection and cursor movement update the status bar; hover shows the fuller explanation.

• payload fields in columns 1-66 are identified as C1, C2, L1, L2, N1, or N2, with parsed ENDF implicit-exponent values
• tail fields in columns 67-80 are identified as MAT, MF, MT, and NS
• common MF and MT numbers are expanded to their ENDF-6 descriptions
• textual references such as MF=3, MF3, MF 12, MT=102, MT1, and MT=52-82 are also explained

Payload field meanings are often record-specific, so the hover reports the reliable fixed-field role unless a standard MF/MT code description applies.

Local Testing

Open this folder in VS Code and press F5, or run Run Extension from the Run and Debug view. In the Extension Development Host, open a local ENDF test file; VS Code should select the ENDF language mode automatically for supported extensions and ENDF-like fixed-column first lines.

Useful sample checks:

• line 2: ENDF numeric HEAD-style fields and MAT/MF/MT tail
• lines 18-19: descriptive MF 12 / MT 102 text
• lines 456-457: SEND and FEND
• lines 5505-5506: MEND and TEND

Use Developer: Inspect Editor Tokens and Scopes in VS Code to inspect the actual TextMate scopes assigned to a token.

Install From Source

Clone the repository and package the extension locally:

npx @vscode/vsce package --no-dependencies
code --install-extension endf-syntax-0.0.1.vsix

Local sample ENDF files used for development checks are ignored by git and are not included in the packaged extension.

Development

The extension entry point is extension.js, the language contribution is declared in package.json, and the TextMate grammar is in syntaxes/endf.tmLanguage.json.

To test changes, open the repository in VS Code and use the provided .vscode/launch.json configuration. Reload the Extension Development Host after grammar or runtime edits.

Issues

Please report bugs and syntax highlighting gaps at https://github.com/tokamaster/vscode_endf/issues.

License

This project is released under the MIT License. See LICENSE for details.

References

• IAEA ENDF-6 format overview
• ENDF-6 Formats Manual, ENDF-102 PDF