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Lexical Elements of the DEC Text Processing Utility Language
4.8 Expressions
There are four types of DECTPU expressions:
•
Arithmetic
•
Relational
•
Pattern
•
Boolean
The following sections discuss each of these expression types.
4.8.1 Arithmetic Expressions
You can use any of the arithmetic operators (+, –, *, / ) with integer data types
to form arithmetic expressions. DECTPU performs only integer arithmetic. The
following are examples of valid DECTPU expressions:
12 + 4
"abc" + "def"
The following is not a valid DECTPU expression because it mixes data types:
"abc" + 12
When performing integer division, DECTPU truncates the remainder; it does not
round. The following examples show the results of division operations:
Expression
39 / 10
-39 / 10
4.8.2 Relational Expressions
A relational expression tests the relationship between items of the same data type
and returns an integer result. If the relationship is true, the result is integer 1; if
the relationship is false, the result is integer 0.
Use the following relational operators with any of the DECTPU data types:
•
Not equal operator (<>)
•
Equal operator ( = )
For example, the following code fragment tests whether string1 starts with a
letter that occurs later in the alphabet than the starting letter of string2:
string1 := "gastropod";
string2 := "arachnid";
IF string1 > string2
THEN
MESSAGE ("Out of alphabetical order ");
ENDIF;
Use the following relational operators for comparisons of integers, strings, or
markers:
•
Greater than operator (>)
•
Less than operator (<)
•
Greater than or equal to operator (>=)
•
Less than or equal to operator (<=)
4–10 Lexical Elements of the DEC Text Processing Utility Language
! adds two integers
! concatenates two strings
! you cannot mix data types
Result
3
-3
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