How do I cast a string to a symbol?

By applying the $ (cast) operator while passing ` (the null symbol) as its left argument:

q)` $ “foo”
`foo
q)

The cast operator also accepts an uppercase type character as its left argument:

q)”S” $ “foo”
`foo
q)

Moreover, you can convert a list of strings at once:

q)”S” $ (“foo”; “bar”; “baz”)
`foo`bar`baz
q)

To go the other way, use the string function:

q)string `foo
“foo”
q)

Since the string function is implemented as the monadic form (i.e., single argument overload) of the k function $ —

q)string
$:
q)

— it is also possible to write the above cast as follows:

q)($)`foo
“foo”
q)

Although we don’t recommend it, we thought you should know in case you see it in the wild.

See also: type