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DEF
Abbreviation: D <SHIFT+E>
TYPE: Statement
FORMAT: DEF FN <name> ( <variable> ) = <expression>
Action: This sets up a user-defined function that can be used
later in the program. The function can consist of any mathematical
formula. User defined functions save space in programs where a
long formula is used in several places. The formula need only
be specified once, in the definition statement, and then it is
abbreviated as a function name. It must be executed once, but
any subsequent executions are ignored.
The function name is the letters FN followed
by any variable name. This can be 1 or 2 characters, the first
being a letter and the second a letter or digit.
EXAMPLES of DEF FN Statement:
10 DEF FN A(X)=X+7
20 DEF FN AA(X)=Y*Z
30 DEF FN A9(Q) = INT(RND(1)*Q+1)
The function is called later in the program by using the function
name with a variable in parentheses. This function name is used
like any other variable, and its value is automatically calculated,
EXAMPLES of FN Use:
40 PRINT FN A(9)
50 R=FN AA(9)
60 G=G+FN A9(10)
In line 50 above, the number 9 inside the parentheses does not
affect the outcome of the function, because the function definition
in line 20 doesn't use the variable in the parentheses. The result
is Y times Z, regardless of the value of X. In the other two functions,
the value in parentheses does affect the result.
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