File trimmers allow only a portion of a file to be read in.
When a file trimmer is used the file looks (to the primitive) as if
the file has been "trimmed" to a smaller size. The "trimming" is done
internal to the Midas framework without modifying the file.
File trimmers are specified by appending them to the end of a file
name but before any qualifiers. For example:
myfile.prm(<start>:<end>)
In the above example <start> is the start position
in the file and <end> is the end position in the
file.
The start/end position can be one of the following:
blank
Use the actual start/end of the file.
myfile.prm(:<end>)
myfile.prm(<start>:)
N
The absolute index (N) into the file.
myfile.prm(N:<end>)
myfile.prm(<start>:N)
-N
Start/end N elements before the end of the file.
myfile.prm(-N:<end>)
myfile.prm(<start>:-N)
~N
Start/end at abscissa value N.
myfile.prm(~N:<end>)
myfile.prm(<start>:~N)
Qualifiers and trimmers can be used at the same time, with trimmers followed by
qualifiers. For example: