In a language, I call something an “indefinite expression” if it denotes multiple values and is grammatically allowed in place of a single-value-denoting expression, causing the semantics of some enclosing phrase to change
Examples:
English: in, “I like everyone”, “everyone” is an indefinite expression
Bash: in
cat ./*, ./* is an indefinite expression
Bash: in
cat ./{here,there}, {here,there} is an indefinite expression
Raku:
all(xs) lt y does not check if all(xs) is less than y, it checks if each x in xs is less than y
SQL: in
WHERE row.id = ANY(...), ANY(...) is an indef expr
Programming: (delimited) continuations can kind of be seen as indefinite expressions
Originally from this Twitter thread