Nested loop with changing parameters values - error

[18...@novasbe.pt]

Hello everyone.

I am new to AMPL. I am trying to execute a loop in two layers  where i am trying to change the initial values of my variables and the values of my parameters in each loop. However I get the error when I try to run I get the following message: "error at _cmdno 40 executing "let" command  a has an = assignment in the model  " This is the structure of my code:

reset;

param a :=1;

var x>=0;

model model.mod;

option solver knitrampl;

repeat {

    for {i in 0..1 by 0.1} {

   let x:=i;

  solve;

  display x , i, a;

}

let a:=a-0.1 ;

}

[Robert Fourer]

You should write "param a default 1;" -- or else just "param a;" and then "let a := 1;" before the repeat. (When you write "param a := 1;" then a is permanently defined as being 1.)

Bob Fourer
am...@googlegroups.com

=======

[18...@novasbe.pt]

Perfect. Thank you very much Robert.