The following functions are built-in to DDS and can be used for the mapping, read or write Definitions:
Function Usage Description
------------------ ------------ ----------------------------------
x+y Addition
x-y Subtration
x*y Mulitplication
x/y Division
x%y Modulo (Remainder of x/y)
x&&y Logical AND
x||y Logical OR
!x Logical Negation
x<<y Bit-wise Left shift
x>>y Bit-wise Right Shift
x&y Bit-wise AND
x|y Bit-wise OR
~x Bit-wise Compliment
x ? y : z Conditional returns y if <x> != 0,
else returns z.
x[y] Subscript x with y
sqrt(x) Returns double value of sqrt of
"x" cast to a double value.
abs(x) Returns double value of absolute
of "x" cast to a double value.
sign(x) Returns 1 if x>0; -1 if x<0; else 0
("x" cast to a double value)
ceil(x) Returns double value of smallest
integer not less than "x".
floor(x) Returns double value of largest
integer not greater than "x".
sin(x) Returns double value of sine of "x"
in radians cast to a double value.
cos(x) Returns double value of cosine of "x"
in radians cast to a double value.
tan(x) Returns double value of tangent of "x"
in radians cast to a double value.
asin(x) Returns double value in radians of
arcsine of "x" cast to a double value.
acos(x) Returns double value in radians of
arccosine of "x" cast to a double value in.
atan(x) Returns double value in radians of
arctangent of "x" cast to a double value.
atan2(x,y) Returns double value in radians of
arctangent of "x/y" cast to a double value.
log(x) Returns double value of natural log
of "x" cast to a double value.
log10(x) Returns double value of base-10 log
of "x" cast to a double value.
exp(x) Returns double value of e**x (ex)
cast to a double value.
pow(x,y) Returns double value of x**y (xy)
cast to a double value.
field(a,b) map: Specify expression "a" if exists
otherwise the value from "b" which
could be "nop" which does nothing.
ident(a) map: Used to specify a field name which
may contain special characters
that could be interpreted by DDS
(eg. "-" in "SHT-X")
linetrc() read:/write: Provide sequential I/O numbers
for each trace starting with 1.
reeltrc() read:/write: Provide sequential I/O numbers
for each trace starting with 1.
This is reset after remounting
a new tape real or disk file.
datestruct(SGRDat) map: Takes a Julian date stored as an
integer (as done with usp header
SGRDat) & converts it to the Date
structure used in segy Date.
dateint(Date) map: Takes the segy Date structure &
converts it to the usp Julian
date integer.
defn_value(dict,name) Pull a value out of Dictionary
eg. defn_value("hist:","delta.x")
ordinal(n) read:/write: Provide sequential ordinal values starting
with 0 for axis number "n". (use
edit:out=force.a to force the ordinal
values; this must be done for all lower
axes as well)
An example of the use of the "field()" function would be in the case:
map:segy:asp.UphlTm= UPHOLE
This mapping would require the member, "UPHOLE", to exist, otherwise an error would result. If there is any doubt, the function, "field()", can be used to guarantee that if a member doesn't exist, then an alternate value would be used. The following example will assign the value in "UPHOLE" to "UphlTm" if "UPHOLE" exists, otherwise nothing is assigned to "UphlTm".
map:segy:asp.UphlTm= field(UPHOLE, nop)