SIMSCRIPT II.5 Programming Language

Programming Language Concepts
2.6 Reading Subscripted Variables
Subscripted variable values can be assigned from input data by including each element of an array
in the variable name list of a read statement. In the following examples, let LIST be a singly subscripted
variable allocated by the statement reserve LIST(*) as 10.
Individual elements of the array are read by listing their names (the array identifier followed by the
appropriate subscript expression(s) enclosed in parentheses) in the list of a read statement. Values
of LIST(1), LIST(5), and LIST(9) are read by the statement:
read LIST(1), LIST(5), LIST(9)
A variable name list can contain array elements whose subscript designators are expressions, such
as LIST(N*M+2/J) or LIST(I), as long as the variables appearing in these expressions have had
values assigned to them. Note that, as the variables named in a read statement are processed from
left to right, variables to be used as subscripts may be assigned if they appear in a read statement
before their subsequent use in the same statement as subscripts, as in:
read N, M, LIST(N), LIST(LIST(N) + M)
This example shows that both unsubscripted and subscripted variables can appear in the same read
statement list.
This procedure is obviously tedious for large arrays, and so provision is also made for reading all
the values of a subscripted array, in order, by including the unsubscripted array name in the list.
Read LIST reads the 10 elements of LIST, as defined by the reserve statement. Numbers are
read and assigned to the elements of LIST in increasing subscript order: the first data item is
assigned to LIST(1), the next to LIST(2), and so on. If LIST were a multidimensional array, the
data would be assigned to successive elements whose subscripts change in increasing order, with
the last subscript position varying most rapidly. A two-dimensional array is read in row-by-row, as
in TABLE(1,1), TABLE(1,2), TABLE(1,3), ..., TABLE(1,N), TABLE (2,1),
TABLE(2,2), ..., TABLE(2,N), etc.
Mixtures of unsubscripted variables, elements of arrays, and entire arrays can be read in one read
statement. In the following example, if LIST and VECTOR are one-dimensional arrays and X and Y
unsubscripted variables, the statement:
read X, LIST(Y), VECTOR
reads a data item and assigns its value to X, reads another data item and assigns its value to
LIST(Y), and then reads as many values as there are elements reserved in VECTOR.
Clearly, the repetition provided by the use of a control phrase is useful when processing the elements
of subscripted variables. Such a control phrase may be used to govern the reading of array
values. The following statement reads N data values, assigning them to the first N elements of the
array LIST:
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