SIMSCRIPT II.5 Programming Language

SIMSCRIPT II.5 Programming Language
substr.f to provide a copy of an embedded character string from a specified position within a
source text string.
Defining a function as "left-handed" indicates that it receives a value, rather than computing one.
SIMSCRIPT II.5 also allows the function substr.f to be used in a left-handed manner. The statement:
let substr.f(STRING,1,3) = "ABC"
replaces the first three character positions in the text variable STRING. The substr.f function
appears to receive, rather than return, a value.
Any function can be defined to be used in both a right- and a left-handed manner. To compute a
value, the right-handed version of the function is called. When a reference is made in a left-handed
manner, that is, to store a value, the left-handed version is called.
No new concepts or statements are involved in the definition of right-handed functions, for all the
functions dealt with thus far have been right-handed. All of the by-now-familiar declarative forms:
function name given argument
function name (argument list)
indicate that the statements that follow, up to the statement end, define a computational process,
hence, a right-handed function. In programs that use both right-and left-handed functions, the word
right may be put before function, but this is optional.
A left-handed function is headed by one of the forms of the routine statement shown above, preceded
by the word left, as in:
and
left function ACCESS given I and J
left function ALLOCATE
In addition to the usual mechanism for transmitting input argument values to a function when it is
called, a left-handed function must have a way of receiving a right-hand-side value. A special statement
of the form:
enter with variable
must be the first executable statement in every left-handed function. It specifies that the value
"computed on the right" and thus transmitted to the left-handed function is to be stored in the named
variable, which can be local or global, unsubscripted, subscripted, or an attribute, for use within the
function. From there on, a left-handed function functions exactly like any other function. It can
store the value, perform computations with it, execute input-output statements, etc. Program 6-3
illustrates the definition and use of right- and left-handed functions.
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