RANK ERROR

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A RANK ERROR is an error message which indicates that an array had an incorrect rank for the way it was used. For example, in most APLs, Iota only accepts a vector or scalar, so giving it a higher-rank array as argument results in a RANK ERROR:

      ⍳2 3⍴⍳6
RANK ERROR
      ⍳2 3⍴⍳6
      ∧

A RANK ERROR can be caused when arguments do not conform because they have differing ranks:

      (2 3⍴2) + ⍳6
RANK ERROR: Mismatched left and right argument ranks
      (2 3⍴2)+⍳6
             ∧

It may also be caused when an array's rank is too small for a function. Windowed Reduction is not defined on scalars:

      2 +/ 0.5
RANK ERROR
      2+/0.5
       ∧

A RANK ERROR may be caused when argument ranks are incompatible in some other way. In languages with high-rank set functions such as Dyalog APL and J, the right argument rank must be at least the left argument rank minus one. Calling it with a matrix left argument and a scalar right argument, which has a rank two smaller, gives a RANK ERROR:

      (⍳3 4) ⍳ ⊂1 3
RANK ERROR
      (⍳3 4)⍳⊂1 3
            ∧
Works in: Dyalog APL


APL features [edit]
Built-ins Primitives (functions, operators) ∙ Quad name
Array model ShapeRankDepthBoundIndex (Indexing) ∙ AxisRavelRavel orderElementScalarVectorMatrixSimple scalarSimple arrayNested arrayCellMajor cellSubarrayEmpty arrayPrototype
Data types Number (Boolean, Complex number) ∙ Character (String) ∙ BoxNamespaceFunction array
Concepts and paradigms Conformability (Scalar extension, Leading axis agreement) ∙ Scalar function (Pervasion) ∙ Identity elementComplex floorArray ordering (Total) ∙ Tacit programming (Function composition, Close composition) ∙ GlyphLeading axis theoryMajor cell search
Errors LIMIT ERRORRANK ERRORSYNTAX ERRORDOMAIN ERRORLENGTH ERRORINDEX ERRORVALUE ERROREVOLUTION ERROR