SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
The failure of any test causes a transfer to one of the cascaded always statements, and hence a
transfer out of the structure. Successive if statements add further logical tests to that of the first
if statement. This structure may be simplified for readability by prefixing the word then to the
second and subsequent if statements, and eliminating all but one of the consecutive always statements.
The example shown above could be written as:
if VALUE > 100.00
let PRIORITY = 2
then if TIME.DUE < 3
add 1 to PRIORITY
then if WORKTIME < 1
add 1 to PRIORITY
always
Note that the then if construct is only applicable to nested logical tests in which the false condition
for any of the tests is to have the same effect — a transfer of control out of the nest structure.
While the use of then if may reduce the number of statements required, the programmer must
judge whether such use obscures the logical intent of the structure.
1.12 More on Logical Expressions
The logical expressions described above have used relational operators to specify comparison between
two arithmetic expressions, or between one such expression and defined properties such as
zero or negative. This section elaborates on the structure of logical expressions.
A logical expression may be negated by following it with the phrase is false, as in the expression:
value < LIMIT is false
The is false phrase may be used to improve readability by stating a desired condition without
forcing an unnatural transposition of logic. For example, a test may be written as:
or:
if QUANTITY > INVENTORY
let ORDER = ORDER - 1
always
if QUANTITY