retrieving values

[MEdan]

I have a basic question:

a['name] vs b[val;'name]

Do I understand the first is a dictionary and I get the value that corresponds to a key "name"? But what data structure is the second? Is that a list? I am reading the code and trying to make sense of what I see.

[davidcrossey]

Hi MEdan,

It depends if your variable is a dictionary or a table as this flips the indexes:

• dictionary = d[key;index]
• table = t[index;key]

For example:

q)d:`name`iq!(`Dent`Beeblebrox`Prefect;98 42 126)
q)d
name| Dent Beeblebrox Prefect
iq  | 98   42         126

q)t:flip d
q)t
name       iq
--------------
Dent       98
Beeblebrox 42
Prefect    126

q)d[;2]
name| `Prefect
iq  | 126
q)d[`name;]
`Dent`Beeblebrox`Prefect
q)d[`name;2]
`Prefect

q)t[2;]
name| `Prefect
iq  | 126
q)t[;`name]
`Dent`Beeblebrox`Prefect
q)t[2;`name]
`Prefect

Passing only the symbol to either dictionary or table will return the associated values key/column:

q)d `iq
98 42 126
q)t `iq
98 42 126

Further reading:

• Tables | Q For Mortals | A textbook forkdb+ and the q programming language - Q for Mortals (kx.com)
• 5. Dictionaries - Q for Mortals (kx.com)

Thanks for posting your query on the portal!

Kind regards,

David