RANK ERROR

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Revision as of 15:05, 17 October 2019 by Miraheze>Adám Brudzewsky
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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 results in a RANK ERROR: <source=apl>

     ⍳2 3⍴⍳6

RANK ERROR

     ⍳2 3⍴⍳6
     ∧

</source>

A RANK ERROR can be caused when arguments do not conform because they have differing ranks: <source=apl>

     (2 3⍴2) + ⍳6

RANK ERROR: Mismatched left and right argument ranks

     (2 3⍴2)+⍳6
            ∧

</source>

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

     2 +/ 0.5

RANK ERROR

     2+/0.5
      ∧

</source>

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: <source=apl>

     (⍳3 4) ⍳ ⊂1 3

RANK ERROR

     (⍳3 4)⍳⊂1 3
           ∧

</source>

Works in: Dyalog APL