# Lookup [Obj,Double]

### Description
Finds all items in `B` whose first column matches `A`.

### Input
- `A [OBJ]`: a list of objects to be searched
- `B [OBJ,DOUBLE]`: a list of pairs to be searched with `A`

### Output
- `B1B2 [OBJ,DOUBLE]`: `B` pairs, where the first column matches items in `A`
- `B2 [DOUBLE]`: `B` values, where the first column matches items in `A`

Output scores can be [aggregated](docs://score_aggregation) and/or [normalised](docs://score_normalisation).