Creating a record from list values

Hi Dicken,  

Great question! The short version is: [] creates a record literal, and on the left side of = inside a record the thing must be a field name, not an expression.

What’s happening

• let ... in [ a = b ]
  Inside [], a is treated as the field name (literally the text "a"), and b is an expression whose value becomes that field’s value. So this returns a record like [a = "1"]. The earlier variable named a is not referenced as a value here; it’s just the field’s label.

• let ... in [ nlist{0}{0} = nlist{0}{1} ]
  Here, nlist{0}{0} is an expression, not a valid field name token. Record literals don’t allow expressions on the left of =. That’s why it errors. It’s not about “list inside a record” vs “single value”; it’s about field-name syntax.

Do this instead, depending on your intent

If you wanted a boolean comparison of the two items:

let
    nlist = { {"One", "1"}, {"Two", "2"} }
in
    nlist{0}{0} = nlist{0}{1}

or, if you want the boolean inside a record:

let
    nlist = { {"One", "1"}, {"Two", "2"} }
in
    [ result = nlist{0}{0} = nlist{0}{1} ]

If you wanted a record with a dynamic field name taken from the list (e.g., field name "One", value "1"):

let
    nlist = { {"One", "1"}, {"Two", "2"} },
    key   = nlist{0}{0},    // "One"
    val   = nlist{0}{1},    // "1"
    rec   = Record.AddField([], key, val)
in
    rec

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Hi Dicken , 

• In [ a = b ], the field name a is treated as a static identifier, so it works.
• In [ nlist{0}{0} = nlist{0}{1} ], you’re asking Power Query to calculate the label first, which it doesn’t allow in that spot.
• If you want a dynamic field name, you must use Record.AddField.

Thanks,

Jai

Hi Dicken 

It is because of general definition of a record.

A rocrd should be including the field name (what is provided befor the equal sign) and then the field value. in your second case, the field name is define as nlist{0} {0} wich is not valied for field name.