### Problem Symbols

The OPTMODEL procedure declares a number of symbols that are aliases for model components in the current problem. These symbols allow the model components to be accessed uniformly. These symbols are described in Table 5.14.

Table 5.14: Problem Symbols

 Symbol Indexing Description _NVAR_ Number of variables _VAR_ {1.._NVAR_} Variable array _NCON_ Number of constraints _CON_ {1.._NCON_} Constraint array _S_NVAR_ Number of presolved variables _S_VAR_ {1.._S_VAR_} Presolved variable array _S_NCON_ Number of presolved constraints _S_CON_ {1.._S_CON_} Presolved constraint array _OBJ_ Current objective _PROBLEM_ Current problem

If the table specifies indexing, then the corresponding symbol is accessed as an array. For example, if the problem includes two variables, `x` and `y`, then the value of _NVAR_ is 2 and the current variable values can be accessed as `_var_` and `_var_`. The problem variables prefixed with _S are restricted to model components in the problem after processing by the OPTMODEL presolver.

The following statements define a simple linear programming model and then use the problem symbols to print out some of the problem results. The `.name` suffix is used in the PRINT statements to display the actual variable and constraint names. Any of the suffixes that apply to a model component can be applied to the corresponding generic symbol.

```proc optmodel printlevel=0;
var x1 >= 0, x2 >= 0, x3 >= 0, x4 >= 0, x5 >= 0;

minimize z = x1 + x2 + x3 + x4;

con a1: x1 + x2 + x3          <= 4;
con a2:               x4 + x5 <= 6;
con a3: x1 +          x4      >= 5;
con a4:      x2 +          x5 >= 2;
con a5:           x3          >= 3;

solve with lp;

print _var_.name _var_ _var_.rc _var_.status;
print _con_.name _con_.lb _con_.body _con_.ub _con_.dual _con_.status;
```

The PRINT statement output is shown in Figure 5.61.

Figure 5.61: Problem Symbol Output

 _VAR_.NAME _VAR_ _VAR_.RC _VAR_.STATUS
1 x1 1 0 B
2 x2 0 1 L
3 x3 3 0 B
4 x4 4 0 B
5 x5 2 0 B

 _CON_.NAME _CON_.LB _CON_.BODY _CON_.UB _CON_.DUAL _CON_.STATUS
1 a1 -1.7977E308 4 4.0000E+00 0 L
2 a2 -1.7977E308 6 6.0000E+00 0 B
3 a3 5 5 1.7977E+308 1 U
4 a4 2 2 1.7977E+308 0 U
5 a5 3 3 1.7977E+308 1 U