User Manual

260
CATC MERLIN’S WAND 1.22 APPENDIX D
User’s Manual CATC Scripting Language
x > 2
which indicates that x is greater than 2. This is a Boolean expression, so it
will evaluate to either true or false. Therefore, if x = 3, then x > 2 will
evaluate to true; if x = 1, it will return false.
True is denoted by a non-zero integer (any integer except 0), and false is a
zero integer (0). True and false are also supported for lists (an empty list is
false, while all others are true), and strings (an empty string is false, while
all others are true), and null is considered false. However, all Boolean
operators will result in integer values.
select expression
The select expression selects the value to which it evaluates based on
Boolean expressions. This is the format for a select expression:
select {
<expression1> : <statement1>
<expression2> : <statement2>
...
};
The expressions are evaluated in order, and the statement that is associated
with the first true expression is executed. That value is what the entire
expression evaluates to.
x = 10
Value_of_x = select {
x < 5 : "Less than 5";
x >= 5 : "Greater than or equal to 5";
};
The above expression will evaluate to "Greater than or equal to 5" because
the first true expression is x >= 5. Note that a semicolon is required at the
end of a select expression because it is not a compound statement and
can be used in an expression context.
There is also a keyword default, which in effect always evaluates to
true. An example of its use is
Astring = select {
A == 1 : "one";
A == 2 : "two";
A == 3: "three";
A > 3 : "overflow";
default : null;