The user may define variables
and functions in the input file, and
apply them subsequently in expressions.
The input file is read sequentially
and variables and functions must be defined before they can be used.
Note carefully that replacement of a variable (or function) by its
value will occur
wherever possible (textually),
even if it leads to non-sense input. A
frequently occurring mistake is that the user defines a variable 'C'
in his (her) input and
then gets his input corrupted because of subsequent isolated C
characters are
replaced by
the defined numerical value.
Therefore: avoid single-character variables and function names.
Always check carefully that the identifier you introduce is not 'used'
already in the input file.
A few variables and functions are pre-defined:
(variables):
pi = 3.1415....
(functions):
sin, cos, tan, asin, acos, atan, exp, log,
sqrt, nint.
The argument list of a function must be enclosed in parentheses, and
the arguments
(in case of more than one)
must be separated by commas.
Defining variables and/or functions is done with the block-type key define.
Example (part of input):
DEFINE
ab = sin(pi/3)
s13 = 14*sqrt(2)
func(x,y,z) = x*ab+y**2-y*z
End
AKEY = FUNC (S13/5, S13/7, SIN(PI/6))
Here a function func and variables ab and s13 are defined, using the
pre-defined functions sin and sqrt,
as well as the pre-defined variable pi. These are then applied to
assign a value to the (hypothetical) key AKEY.
Note 1: the variable ab is also used in the definition of func'; this
is allowed because ab is defined before func.
Note 2: variable- and function names
must have the same form as keywords, i.e. only certain characters
are allowed.
Note 3: in the definition of variables and functions blanks are ignored
altogether (in the value part) and will
not be interpreted as possible
separators of the expression that defines the variable or function.
Definition of user-supplied functions and variables that can subsequently be used in the input file. (see the note on auxiliary input features)
