ISLOGICAL Function (Gnumeric)

ISLOGICAL returns TRUE when the value it tests is a genuine Boolean TRUE or FALSE; it returns FALSE for numbers or ordinary text that merely resembles a Boolean. Gnumeric stores Boolean, numeric and text elements as distinct cell value types. R1

=ISLOGICAL(value)

value (required) may be a value, an expression or a reference to a cell containing a value. There is one required parameter, with no optional arguments or default values. Gnumeric’s own help identifies the result as a logical TRUE/FALSE, and the inspected source tests whether the evaluated argument is typed as a Boolean; it does not simply check whether a value is nonzero. R1

Native-validation limits: All outputs are source/documentation-based expectations, not native Gnumeric observations.

Version and locale scope: Written against the official Gnumeric 1.12 Information manual, the public Gnumeric function catalogue and the GNOME-maintained source consulted on 2026-10-12. Gnumeric 1.12.62 is the current series release identified. Actual plugin/build availability and any localization effects must be confirmed in the reader’s installation. These guides use English names and Gnumeric’s manual convention of a leading = and comma-separated arguments. A single-argument function has no delimiter ambiguity; nested IF examples use commas and might need locale-appropriate adjustment. R1R4

1. Enter the entries in A2:A6 below. Enter TRUE/FALSE without quotation marks for Boolean cells; for the text row, begin the input with an apostrophe ' so Gnumeric stores text instead of interpreting a Boolean. Leave A7 empty.
2. Enter =ISLOGICAL(A2) in B2 and fill through B7.
3. Compare the displayed outcomes with the expected logical results below; actual native execution remains pending.

Gnumeric’s manual explicitly explains Boolean entry and recognizes a leading apostrophe to force text. The TRUE/FALSE type classifications and expected outputs follow the function’s documented test and source predicate; no native Gnumeric worksheet was executed. R1R6

Suppose A2:A7 is an audit/import column in which only true Boolean flags should count. In C2, enter and fill down:

=IF(ISLOGICAL(A2),"Valid Boolean","Check input type")

For the example rows, the expected labels are Valid Boolean, Valid Boolean, Check input type, Check input type, Valid Boolean, and Check input type. The text 'TRUE row is flagged even though its letters look right. This is useful before logic-dependent calculations, especially when CSV imports leave values as text. The compound IF example is logically calculated rather than natively tested. R1

Boolean result versus its truth value

=ISLOGICAL(FALSE()) is expected TRUE: this is a type test, not a test for a true condition. Conversely, =ISLOGICAL("FALSE") is expected FALSE, because quoted characters are a string. To ask whether a value is TRUE or FALSE as a condition, use the Boolean value or another logical expression rather than using ISLOGICAL as a truth check. R1R6

Label a computed comparison

=ISLOGICAL(8>3) is expected TRUE, because the comparison itself produces a Boolean. =ISLOGICAL(8+3) is expected FALSE, because arithmetic produces a number. These expectations follow the Gnumeric types described in the manual. R1

• FALSE input returns TRUE: the question is is this Boolean?, not does this evaluate to true? R1
• 1 or 0 unexpectedly returns FALSE: Gnumeric’s own manual distinguishes numbers from Booleans, and the function checks the Boolean type. Avoid coercing numeric flags by assumption. R2
• Quoted TRUE returns FALSE: text 'TRUE and logical TRUE are distinct values; review import types and number formats. R2
• Error cells: the exact user-visible behavior when the argument itself is an error was not native-tested in this run. Check this case on the installed version rather than borrowing Excel/LibreOffice error propagation rules.
• Blank cells or whitespace: a truly blank cell is not a Boolean; a text cell containing spaces is also not a Boolean. Confirm any unexpected result by viewing underlying content. R2
• Locale: use the documented function name in the target installation. This function itself takes just one argument; the example IF formulas use the manual’s English comma convention. R4

Gnumeric’s manual explicitly describes ISLOGICAL as Excel compatible, and its public catalogue classifies it as Complete / Basic project tests. That is not proof this tutorial was tested, nor a guarantee of identical behavior in every Excel, LibreOffice or browser-based edition. Microsoft’s current Excel Information reference separately lists ISLOGICAL. R1R7

ISNUMBER · ISTEXT · ISNONTEXT · IF · TRUE · FALSE.

Checked: 2026-10-12 UTC. These official references support the specific claims above:

• R1 Gnumeric Information functions — official function definitions, signatures, argument descriptions and compatibility notes.
• R2 Gnumeric cells, formulas, references and errors — formula input, Boolean versus text values, cell references and error interpretation.
• R3 Gnumeric public function catalogue — registration, implementation and project test-suite classification; catalogue totals are not the version-pinned 1.12.62 release registry.
• R4 Gnumeric locales — operating-system locale and formatting context.
• R5 Gnumeric 1.12.62 release announcement — current version context; this does not prove execution of these examples on every build.
• R6 Official Gnumeric 1.12.62 source archive — checksum-verified plugins/fn-info/functions.c help and callbacks inspected on 2026-10-13; source-level evidence, not native execution.
• R7 Microsoft’s Excel Information function reference — Excel’s separately documented availability, not a substitute for testing Gnumeric.

Validation: Official manuals and checksum-verified Gnumeric 1.12.62 source were inspected; expected outcomes were logically evaluated. No native Gnumeric execution, screenshots, locale regression or workbook round-trip tests were performed.