SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
function SQUARE.ROOT given NUMBER
let SQRT = NUMBER/2.0
let DELTA = SQRT
until DELTA < 0.00001 * SQRT)
do
let SQRT = (SQRT + NUMBER/SQRT)/2.0
let DELTA = ABSOLUTE(NUMBER/SQRT - SQRT)
loop
return with SQRT
end
By incorporating the function reference directly in the logical control phrase and eliminating the
evaluation of the intermediate result, DELTA, this example reduces to:
function SQUARE.ROOT given NUMBER
let SQRT = NUMBER/2.0
until ABSOLUTE(NUMBER/SQRT - SQRT) < (0.00001 * SQRT)
let SQRT = (SQRT + NUMBER/SQRT)/2.0
return WITH SQRT
end
Function evaluation takes the same precedence as subscripted variable evaluation. The function is
evaluated prior to evaluation of the expression in which the function appears. Obviously, expressions
appearing as arguments to the function are independently evaluated before the function evaluation.
2.14 Global and Local Variables, Routines, Functions, and Side Effects
It has been suggested that communication of values between routines is best done through an explicit
argument list. The interactions between a number of routines using many global variables can
be hard to follow, and a single error may have widespread repercussions. The use of explicit arguments
helps to logically separate the task of a single routine within the entire program. When global
variables are used in routines that interact, care must be exercised to prevent unwanted side effects.
Most rigorously, any change in the value of any nonlocal variable may be termed a side effect.
More commonly, the term refers to an unexpected or unforeseen consequence of any statement,
usually involving a routine or function call. The practice of explicitly declaring all local variables
to a routine helps avoid the inadvertent modification of any global variables.
2.15 Library Functions
Some functions, such as the square root and absolute value, are used so frequently that they are incorporated
in the SIMSCRIPT II.5 language. A list of these functions appears in Appendix B. To
help distinguish the use of these functions, the names are formed from mnemonic abbreviations suffixed
with the two characters .f. For example, abs.f returns the absolute value of the given argument,
sqrt.f returns the square root, and log.e.f returns the natural logarithm. Recall that
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