Description
Return a singleton mask's bit index or a sentinel.
Bit positions are usually counted from the least-significant bit, while a displayed binary string has its own left-to-right indexing convention. Masks, fields and parity predicates describe a selected region or pattern; local agreement does not validate a complete encoded record.
Return a singleton mask's bit index or a sentinel.
When to use this tool
Use Bitwise: Bitmask Singleton Index Check when checking the stated mask, field, parity or bit-index convention.
How to use the tool and how it works
- Enter mask, width. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read result. Expand result to inspect the returned fields.
Return a singleton mask's bit index or a sentinel. Validate bounded mask; singleton means nonzero with mask AND (mask-1) zero, index is its set-bit position or -1 otherwise.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| mask | Mask | Required. Text. Integer syntax: optional + or - and 1-128 decimal digits; leading zeros accepted. Apply the sign restriction above. Implementation limit: 8192 Unicode code points and 16384 UTF-16 code units. Word value must satisfy 0 <= value < 2^width. |
| width | Width under the stated bit, interval or geometry convention; apply the field-specific units and bounds. | Required. Safe integer. Fixed-word implementation domain: whole width 1-128 bits. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| result | Returned calculated value or nested object under the stated output convention. | Required. Object. |
| result.singleton | Singleton | Calculated result member: boolean. |
| result.index | Zero-based singleton bit position from the least-significant end, or -1 when not singleton. | Calculated result member: number. |
{
"input": {
"mask": "8",
"width": 8
},
"output": {
"result": {
"singleton": true,
"index": 3
}
}
}Limitations and assumptions
- Zero and multi-bit masks are successful false results, not invalid inputs or index zero.
- Outputs are nested inside result. Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Choose an explicit bit order, word width and missing-position policy; use the complete record format and appropriate parsing or checksum methods for full validation.
References
Similar or alternative tools
- Gray Code Single Transition Bit Index
Check whether two words differ in exactly one bit.
- Lowest Zero Bit Index
Return the least-significant zero-bit index.