5.9.8.4 Const-does>

A frequent use of create...does> is for transferring some values from definition-time to run-time. Gforth supports this use with

const-does>       run-time: w*uw r*ur uw ur "name" –         gforth       “const-does>”

Defines name and returns.

name execution: pushes w*uw r*ur, then performs the code following the const-does>.

A typical use of this word is:

     : curry+ ( n1 "name" -- )
     1 0 CONST-DOES> ( n2 -- n1+n2 )
         + ;
     
     3 curry+ 3+

Here the 1 0 means that 1 cell and 0 floats are transferred from definition to run-time.

The advantages of using const-does> are:

• You don't have to deal with storing and retrieving the values, i.e., your program becomes more writable and readable.
• When using does>, you have to introduce a @ that cannot be optimized away (because you could change the data using >body...!); const-does> avoids this problem.

An ANS Forth implementation of const-does> is available in compat/const-does.fs.