Table 20. Rules for Names
Name
Category
1
Maximum Length
(number of
characters)
Allowed characters
Units 38
or underscore. CRBasic is not case sensitive.
Units are excepted from the above rules. Since
units are strings that ride along with the data,
they are not subjected to the stringent syntax
checking that is applied to variables, constants,
subroutines, tables, and other names.
Alias 39
Station name 64
Data-table name 20
Field name 39
Field-name
description
64
1
Variables, constants, units, aliases, station names, field names, data table names, and file names
can share identical names; that is, once a name is used, it is reserved only in that category. See
the section Predefined Constants
(p. 138) for another naming limitation.
7.8.4.14 Expressions in Arguments
Read More See Programming Express Types (p. 160) for more information on
expressions.
Many CRBasic instruction parameters allow the entry of arguments as
expressions. If an expression is a comparison, it will return -1 if true and 0 if false.
(See the section Logical Expressions
(p. 164)). The following code snip shows the
use of an expressions as an argument in the TrigVar parameter of the
DataTable() instruction:
'DataTable(Name, TrigVar, Size)
DataTable(Temp, TC > 100, 5000)
When the trigger is TC > 100, a thermocouple temperature greater than 100 sets
the trigger to True and data are stored.
7.8.4.15 Programming Expression Types
An expression is a series of words, operators, or numbers that produce a value or
result. Expressions are evaluated from left to right, with deference to precedence
rules. The result of each stage of the evaluation is of type Long (integer, 32 bits) if
the variables are of type Long (constants are integers) and the functions give
integer results, such as occurs with INTDV(). If part of the equation has a
floating point variable or constant (24 bits), or a function that results in a floating
point, the rest of the expression is evaluated using floating-point, 24-bit math,
even if the final function is to convert the result to an integer, so precision can be
lost; for example, INT((rtYear-1993)*.25). This is a critical feature to consider
when, 1) trying to use integer math to retain numerical resolution beyond the limit
of floating point variables, or 2) if the result is to be tested for equivalence against
another value. See section Floating-Point Arithmetic
(p. 161) for limits.
Two types of expressions, mathematical and programming, are used in CRBasic.
A useful property of expressions in CRBasic is that they are equivalent to and
often interchangeable with their results.
160
To Next Page
Loading...
Need help?
General
