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General HydroStatics
Ship Stability Software |
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Command of the Week
(New or interesting aspects of GHS that you may not know about) |
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Variables in Part Maker
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John Bonn noticed the example in
COW016, and he became very excited about the advantages of
embedding variables and expressions in his
geometry definitions. But he came to us complaining that COW016 was
actually no help
to him because it didn't tell him where and how to define
variables and when to use PMX vs. PM.
Well, we had to agree with him. John suggested that we make another stab at it, keeping it as simple as possible -- which we've done, and here it is. PM can make use of variables defined in the GHS main program. For example, |
variable diam=10
enter pm
create ball
class hull
sphere 0 0 0 {diam}
/
write ball.gf
quit pm
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The reason this works is not obvious.
Before handing the PM portion of the run file off to Part Maker,
GHS processes it, substituting variable values where indicated.
But variables can be defined in Part Maker, making the pre-processing unnecessary. Pre-processing can be turned off by including the /DIRECT parameter. For example, |
enter pmx /direct real diam:=10 create ball class hull sphere 0, 0, 0, diam / write ball.gf quit pm |
| Notice that this uses PMX, which requires separators between parameters (not just spaces). This makes it possible to use arithmetic expressions. For example, |
enter pmx /direct real radius:=5 create ball class hull sphere 0, 0, 0, radius*2 / write ball.gf quit pm |
| The /DIRECT is optional in these examples because there is nothing for the pre-processing to change. But if macros are involved, without the /DIRECT they will disappear and be replaced by their contents. This usually works, but it limits what the macros can do. For example, |
enter pmx /direct macro make create %1 class hull sphere 0, 0, 0, 10 // / str name:="ball" .make name write ball.gf quit pm |
| Without the /DIRECT, the name will not be "ball" as intended because "name" will be passed as a literal. |
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Questions, comments, or requests?
Contact Creative Systems, Inc. USA phone: 360-385-6212 Fax: 360-385-6213 Office hours: 7:00 am - 4:00 pm Pacific Time, Monday - Friday Mailing address: PO Box 1910 Port Townsend, WA 98368 USA Click here for an index to this and previous COWs |