Alter Query¶

The alter function modifies elements at specific indices in Vectors, Lists, or Tables using a function. It applies the function to the element at the specified index with a given value.

(set prices [100 200 300])
[100 200 300]

(set prices (alter prices + 1 10))
[100 210 300]

The alter function takes 3-4 arguments:

The object to modify (vector, list, or table)
A binary Function to apply
An optional index (if omitted, applies to all elements)
A value to use with the function

Working with Tables¶

When working with Tables, specify the column name as a symbol:

(set trades (table [price volume] (list [100 200] [50 60])))

(set trades (alter trades + 'price 10))  ;; Add 10 to all values in the price column

(select {price: price volume: volume from: trades})
┌───────┬────────┐
│ price │ volume │
├───────┼────────┤
│ 110   │ 50     │
│ 210   │ 60     │
└───────┴────────┘

In-Place Modification¶

To modify the object in place without reassigning, pass the object name as a quoted Symbol:

(set prices [100 200 300])

(alter 'prices + 10)

Important: Persisting Changes

By default, alter returns a modified copy and does not modify the original. To persist changes, you have two options:

Reassign the result:
```
(set prices (alter prices + 10))
```

Use in-place modification with quoted symbol:

(alter 'prices + 10)  ;; Modifies prices directly