const

const, keyword, assignment option

The const keyword indicates that the value taken by a variable is known at compile time and that it won’t change later at runtime. Those variables are primarily intended to control the files being read.

const myFolder = "/foo"

read "\{myFolder}/products.csv" as Products with
  Product: text
  Price: number

Notably, the read block requires a text value for its file path that evaluates as const.

const, keyword, pure function option

The const keyword indicates that the pure function can be executed at compile time.

def const pure myInc(a: number) with 
  return a + 1

const x = myInc(42)

show scalar "" with x

In the present reference documentation, pure functions that are part of the Envision standard library and that can be executed at compile time are marked as const.