under - SuperDB

under — the underlying value

under(val: any) -> any

The under function returns the value underlying the argument val:

for unions, it returns the value as its elemental type of the union,
for errors, it returns the value that the error wraps,
for name-typed values, it returns the value with the named type’s underlying type,
for type values, it removes a named type if one exists; otherwise,
it returns val unmodified.

Unions are unwrapped

# spq
values this
# input
1::(int64|string)
"foo"::(int64|string)
# expected output
1::(int64|string)
"foo"::(int64|string)

# spq
values under(this)
# input
1::(int64|string)
"foo"::(int64|string)
# expected output
1
"foo"

Errors are unwrapped

# spq
values this
# input
error("foo")
error({err:"message"})
# expected output
error("foo")
error({err:"message"})

# spq
values under(this)
# input
error("foo")
error({err:"message"})
# expected output
"foo"
{err:"message"}

Values of named types are unwrapped

# spq
values this
# input
80::(port=uint16)
# expected output
80::(port=uint16)

# spq
values under(this)
# input
80::(port=uint16)
# expected output
80::uint16

Values that are not wrapped are unmodified

# spq
values under(this)
# input
1
"foo"
<int16>
{x:1}
# expected output
1
"foo"
<int16>
{x:1}

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