[Help-glpk] Problem with parameter spec

[Kostas Oikonomou]

Hi,

I am running GLP 4.8 on the two simple files that follow, and getting the 
following
error:

bash-2.05$ glpsol --model t.mod --data t.dat
Reading model section from t.mod...
13 lines were read
Reading data section from t.dat...
t.dat:3: s requires numeric data
Context:                                set V := A B C ; param s := A
Model processing error
bash-2.05$

I've read the manual a number of times, but I can't understand why this is
happening.  Is there some reason that a parameter can't be a string?

Any hints would be appreciated.


                            Kostas Oikonomou


===================================================

set V;
set E within V cross V;
param s in V;
param d in V;
param c{(a,b) in E};
var x{(a,b) in E}, >=0;

minimize length : sum{(a,b) in E} c[a,b]*x[a,b];
subject to
  flow{a in V}: sum{(b,a) in E} x[b,a] + (if a = s then 1) =
                sum{(a,b) in E} x[a,b] + (if a = d then 1);

end;


===================================================

set V := A B C;
param s := A;
param d := C;
set E :=
  A B
  A C
  B C
;
param c :=
  A B  10
  A C  20
  B C  5
;
end;