Index Origin ⎕IO

⎕IO determines the index of the first element of a non-empty vector.

⎕IO may be assigned the value 0 or 1.  The value in a clear workspace is 1.

⎕IO is an implicit argument of any function derived from the Axis operator ([K]), of the monadic functions Fix (⎕FX), Grade Down (), Grade Up (), Index Generator (), Roll (?), and of the dyadic functions Deal (?), Grade Down (), Grade Up (), Index Of (), Indexed Assignment, Indexing, Pick () and Transpose ().

Examples

        ⎕IO←1
        ⍳5
1 2 3 4 5
 
        ⎕IO←0
        ⍳5
0 1 2 3 4
 
        +/[0]2 3⍴⍳6
3 5 7
 
        'ABC',[¯.5]'='
ABC
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