The HIDE command hides the text of a model from viewing by the user. This may be useful if you are trying to protect proprietary ideas contained in your model.

When you enter the HIDE command, you’ll be prompted for a password. You may enter any password with up to eight characters. LINGO will prompt you for this password once more for verification. LINGO is sensitive to the case of the alphabetic characters in the password.

Once a model is hidden, commands allowing the user to view the model text (e.g, GEN, LOOK, SMPS) are disabled. All other commands, however, will function as normal with the exception of ALTER.  If a model is hidden, ALTER will perform modifications, but they will not be echoed to the screen.

When a hidden model is saved to disk, its text will be encrypted. This prevents the user from viewing the model from outside of LINGO as well. You will want to distribute the encrypted version of the model to those using your application. However, you should always keep an unhidden version of the model at your site for safekeeping in the event you forget the password.

A hidden model may be returned to the normal unhidden state by once again issuing the HIDE command with the correct password.

A sample session illustrating the use of the HIDE command follows:

: TAKE TRAN.LNG         !Read in a model

: LOOK 4 6              !Display some rows

  4]   SUPPLY / WH1, WH2, WH3/  : CAP;

  5]   DEST / C1, C2, C3, C4/ : DEM;

  6]   LINKS( SUPPLY, DEST) : COST, VOL;

 

: HIDE        !Now hide the model

Password?

TIGER

Please reenter password to verify:

TIGER

Model is now hidden.

 

: ! Model is hidden so LOOK will fail

: LOOK ALL

 

[Error Code:  111]

 

Command not available when model is hidden.

 

: ! We can still solve it though

: TERSE

: GO

 

Global optimal solution found at step:         6

Objective value:                        161.0000

 

: !And get a solution report

: NONZ VOL

 

    Variable         Value      Reduced Cost

VOL( WH1, C1)      2.000000          0.000000

VOL( WH1, C2)      17.00000          0.000000

VOL( WH1, C3)      1.000000          0.000000

VOL( WH2, C1)      13.00000          0.000000

VOL( WH2, C4)      12.00000          0.000000

VOL( WH3, C3)      21.00000          0.000000

 

: !Now, unhide the model

: HIDE

Password?

TIGER

 

Model is no longer hidden.

 

: !Once again, we can view the model

: LOOK 4 6

  4]   SUPPLY / WH1, WH2, WH3/  : CAP;

  5]   DEST / C1, C2, C3, C4/ : DEM;

  6]   LINKS( SUPPLY, DEST) : COST, VOL;

 

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