Throw codes from to

[ruv]

Preamble

In the standard, the Table 9.1: THROW code assignments contains the line:

• -32 invalid name argument (e.g., TO name)

The term «name» refers to a parameter in the stack diagram, e.g. for TO:

• Interpretation: ( i*x "<spaces>name" -- )
• Compilation: ( "<spaces>name" -- )

This is the so-called parsed-text notation, in which:

• name: a token delimited by space, equivalent to «ccc<space>» or «ccc<eol>»

Side note: in the word name parse-name, «name» refers to a token delimited by space (a lexeme). But in the word names name>, find-name, find-name-in, name>string, name>compile, name>interpret, «name» refers to the name token (nt). This is an inconsistency in naming.

So, "name argument" is an immediate argument from the input source. For example, in the phrase «to xxx», "xxx" is an immediate argument.

Update: in some cases a name argument is not an immediate argument. For example, if a word is an ordinary word such as «'», «constant», and it's used in a definition body.

Question

The word to might detect the following problems with its immediate argument:
— a word with this name is not found in the search order;
— a word is found, but it is not created with value (or a such), i.e., "TO name" semantics are not defined for this word.

My question is: what throw code would be best for each of these cases?

The candidates are:

• -13 undefined word
• -32 invalid name argument (e.g., TO name)
• -21 unsupported operation (e.g., AT-XY on a too-dumb terminal)

What are your arguments in favor of using one option or another?