Constants in Io

constant.io

Constant := Object clone do (
  with := method(msg, 
    self msg := msg
    self activate := method(call message setName(msg asString); msg)
  )
)

// Lets try it out:
// Make PI a regular number

PI := 3.1415926

// Make b a method that uses it

b := method(PI+PI)

writeln(b) // -> 6.283185

// Inspect bs "source" code

writeln(getSlot("b") code) // -> block(PI +(PI))

// Make PI a constant

PI := Constant with(3.1415926)

writeln(b) // -> 6.283185
writeln(getSlot("b") code) // -> block(3.141593 +(3.141593))

// Still works but when we look at the code of b we see that
// the PIs have been replaced with PIs value!!!