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NUMBER, STRING, and SET Parameter Declarations

NUMBER parameter-decl [, ...parameter-decl] ;

STRING parameter-decl [, ...parameter-decl] ;

SET [ <scalar-type, ...scalar-type >] parameter-decl [, ...parameter-decl] ;

NUMBER | NUM

STRING | STR

SET [ <scalar-type, ...scalar-type >]

name [ { index-set } ] [ parameter-option(s) ]

= expression

This option provides an explicit value for each parameter location. In this case the parameter acts like an alias for the expression value.

INIT expression

This option specifies a default value that is used when a parameter value is required but no other value has been supplied. For example:

  
    number n init 1; 
    set s init {'a', 'b', 'c'};
 

PROC OPTMODEL evaluates the expression for each parameter location the first time the parameter needs to be resolved. The expression is not used when the parameter already has a value.

= [ initializer(s) ]

This option provides a compact means to define the values for an array, in which each array location value can be individually specified by the initializers.

  
    proc optmodel; 
       number n; 
       set<number> s = 1..n; 
       number a{s}; 
       n = 3; 
       a[1] = 2;    /* OK */ 
       a[7] = 19;   /* error, 7 is not in s */ 
       n = 10; 
       a[7] = 19;   /* OK now */
 

    proc optmodel;
       num a{i in 1..2} init i**2;
       a[1] = 2;
       put a[*]=;
 

                                                                                
                                                                                 
                                                                                 
 a[1]=2 a[2]=4                                                                   
 

Initializing Arrays

    proc optmodel;
       number a{1..3} = [5 4 7];
       put a[*]=;
 

                                                                                
                                                                                 
                                                                                 
 a[1]=5 a[2]=4 a[3]=7                                                            
 

[ [ index ] ] value

The value specifies the value of an array location and can be a numeric or string constant, a set literal, or an expression enclosed in parentheses.

In array initializers, string constants can be specified using quoted strings. When the string text follows the rules for a SAS name, the text can also be specified without quotation marks. String constants that begin with a digit, contain blanks, or contain other special characters must be specified with a quoted string.

As an example, the following code defines an array parameter that could be used to map numeric days of the week to text strings:

  
    proc optmodel; 
       string dn{1..5} = 
              [Monday Tuesday Wednesday Thursday Friday];
 

The optional index in square brackets specifies the index of the array location to initialize. The index specifies one or more numeric or string subscripts. The subscripts allow the same syntactic forms as the value items. Commas can be used to separate index subscripts. For example, location a[1,'abc'] of an array a could be specified with the index [1 abc]. The following example initializes just the diagonal locations in a square array:

  
    proc optmodel; 
       number m{1..3,1..3} = [[1 1] 0.1 [2 2] 0.2 [3 3] 0.3];
 

An index does not need to specify all the subscripts of an array location. If the index begins with a comma, then only the right-most subscripts of the index need to be specified. The preceding subscripts are supplied from the index that was used by the preceding initializer . This can simplify the initialization of arrays that are indexed by multiple subscripts. For example, you can add new entries to the matrix of the previous example by using the following code:

  
    proc optmodel; 
       number m{1..3,1..3} = [[1 1] 0.1            [,3] 1 
                                        [2 2] 0.2  [,3] 2 
                                                  [3 3] 0.3];
 

The spacing shows the layout of the example array. The previous example was updated by initializing two more values at m[1,3] and m[2,3].

If an index is omitted, then the next location in the order of the array's index set is initialized. If the index set has multiple index-set-items , then the rightmost indices are updated before indices to the left are updated. At the beginning of the initializer list, this is the first member of the index set. The index set must use a range expression to avoid unpredictable results when an index value is omitted.

The initializers can be followed by commas. The use of commas has no effect on the initialization. The comma can be used to clarify layout. For example, the comma could separate rows in a matrix.

Not every array location needs to be initialized. The locations without an explicit initializer are set to zero for numeric arrays, set to an empty string for string arrays, and set to an empty set for set arrays.

Note: An array location must not be initialized more than once during the processing of the initializer list.