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Vex

#REF!: an address outside the space

#REF! means that an address or an axis points to a key that the space does not have. A spreadsheet gives the same code for a reference to a cell that does not exist.

A reference to the key Zorigin
ref("position", [key("Z")])
step 1 of 1

Result at A: #REF! the space has no key "Z"

originABCD
result#REF! unknown-key#REF! unknown-key#REF! unknown-key#REF! unknown-key

The program reads position at the key Z. The space has the keys A, B, C and D, so the address fails at each origin. The error has the path of the reference node, the origin and the focus.

Kinds

Section titled “Kinds”
Kind Cause
unknown-key The move key(k) goes to a key that the space does not have. An origin that is not a key also gives this kind.
not-a-pair The move other or the axis other is in a space that does not have two keys.
out-of-bounds The move index(i) or offset(d) goes outside the space.
no-offset The move offset(d) is in a record space, or d has the wrong number of values.
no-grid The axis neighbors is in a space that is not a grid.

How the types prevent it

Section titled “How the types prevent it”

The typed builder accepts only the keys of the space. root.of("Z", "position"), .to("Z") and .at("Z") do not compile. other() exists only on a chain over a pair. Thus the program above is possible only as IR, for example from JSON.

const root = vex(Vec2Domain).over(space.record({ A, B, C }));


root.from("position")._.add(root.of("Z", "size")); // type error: "Z" is not a key
root.from("position").other();                     // type error: the space is not a pair

The fix

Section titled “The fix”
  • Use a key of the space. For a key from outside the program, check it with space.has(k) before the evaluation.
  • At the edge of an array or a grid, give a fallback with ifError, like IFERROR in a spreadsheet.
  • For a pair axis, make a space with two keys.

Refer to error values for the other codes.