Leftmost Longest Literal Match Selector

Select nonoverlapping leftmost-longest literal alternatives; equal lengths retain input alternative order.

Description

Select nonoverlapping leftmost-longest literal alternatives; equal lengths retain input alternative order.

Competing literal matches need a consistent selection policy. Leftmost-longest selection chooses the longest option at the current position before continuing past it.

When to use this tool

Select nonoverlapping leftmost-longest literal alternatives; equal lengths retain input alternative order.

Prepare the supplied text, needles fields for this operation.
Compare the complete example with the representation used by your own input before carrying the result into another step.

How to use the tool and how it works

Enter text, needles. Use the exact text syntax, units and index conventions explained below.
Run the tool. If input validation fails, correct the supplied fields before interpreting any result.
Read result.selected. Interpret false, null and empty lists using the distinctions below; they can be valid outputs.

At each UTF-16 offset, find matching nonempty needles, choose the longest and break equal-length ties by needle-list order. Emit offset, needleIndex and matched text, then advance past the selected match.^[1]

Input field	Meaning and representation	Accepted input
text	text.	Text; at most 8,192 UTF-16 code units, subject to the grammar above
needles	needles.	At most 128 strings, each at most 128 UTF-16 code units

Output field	Interpretation
result	Object containing the named outputs below.
result.selected	The selected list in the ordering and representation described above.

json

{
  "input": {
    "text": "ababa",
    "needles": [
      "a",
      "ab"
    ]
  },
  "output": {
    "result": {
      "selected": [
        {
          "offset": 0,
          "needleIndex": 1,
          "text": "ab"
        },
        {
          "offset": 2,
          "needleIndex": 1,
          "text": "ab"
        },
        {
          "offset": 4,
          "needleIndex": 0,
          "text": "a"
        }
      ]
    }
  }
}

Limitations and assumptions

Selected matches do not overlap. The tool does not apply regex syntax, case folding or Unicode normalization; an empty needle list or empty needle is rejected.
Text offsets and lengths use UTF-16 code units unless explicitly described as bytes or code points. CRLF, CR and LF are recognized as line endings; a terminal newline creates a final empty line in the shared line model.
Every declared top-level field is required and unexpected fields are rejected. Numeric inputs must be finite; ordinary text fields are bounded to 8,192 UTF-16 code units, with tighter operation-specific limits where stated.
Ordinary string lists have at most 128 entries of at most 128 code units each; numeric lists and matrices have separate bounded size checks. Nonfinite results and excessively large serialized outputs are rejected.
Indexes are zero-based and spans have an exclusive end unless explicitly stated otherwise. A valid false, null or empty-list result is distinct from malformed input.

Alternative or Complementary methods

Use a parser or language-aware editor when quoting, syntax or nested constructs matter. For plain text transforms, keep UTF-16 offsets, Unicode code points, grapheme clusters and UTF-8 byte offsets distinct; apply changes to the same source version used to calculate spans.

References

Tool behavior and example: Leftmost Longest Literal Match Selector — tool.io

Similar or alternative tools

Overlapping Literal Match Indexes
Return overlapping literal-match UTF-16 offsets; distinct from a nonoverlapping replacement operation.
Enclosing Literal Wrapper Stripper
Strip one complete nonoverlapping enclosing literal wrapper, never internal or partial matches.