Common Errors¶

SYNTAX ERROR (code 1)¶

The expression could not be parsed.

Common causes: unmatched braces or brackets, missing argument, invalid token, misplaced operator.

      1 + + 2
SYNTAX ERROR

A name has no assigned value.

Common causes: typo in a function or variable name, using a name before assigning it.

      x + 1
VALUE ERROR: Undefined variable: x

The function received an argument outside its domain.

Common causes: division by zero (1÷0), logarithm of zero or negative number, singular matrix in ⌹.

      1÷0
DOMAIN ERROR: Division by zero

Array shapes do not match for a dyadic operation.

Common causes: 1 2 3 + 1 2 (different lengths), mismatched matrix dimensions in inner product.

      1 2 3 + 1 2
LENGTH ERROR: Shape mismatch: [3] vs [2]

The operation is not valid for the array's rank.

Common causes: applying ⌷ (From) to a scalar, transpose of rank > 2, monadic ⍳ on a non-scalar.

      1⌷5
RANK ERROR: requires non-scalar right argument

An index is out of range.

Common causes: index larger than axis length, index less than or equal to 0 with ⎕IO←1.

      V ← 1 2 3
      V[4]
INDEX ERROR

An I-Beam call was blocked by the allowlist.

Cause: the MARPLE_IBEAM_ALLOW environment variable is set and the requested module path is not on the allowlist.

Attempt to change the name class of an existing binding (e.g., assigning an array to a name that currently holds a function).

      f ← {⍵+1}
      f ← 5
CLASS ERROR