LINGO Interactive Execution
Lingo is basically designed for interactive execution. In this section, an annotative sample of interactive execution is addressed. Annotation is given after ! sign. The ! sign is the symbol for comments, which must end with a semi-colon [unlike Gino]. Lingo will ignore all the command or comment after the ! sign. The other main difference from Gino is that all functions in Lingo begin with @ [for example, @ABS, rather than ABS, denotes the absolute value function].
: ! The prompt is a colon; : ! The Lingo system is case insensative; : ! MODEL is the command used to signify the beginning of model input; : ! : model ! The prompt changes to a question mark, as the model is entered; ? min=2*x+3*y; ! MIN is the reserved keyword meaning minimum in a model; ? x+y>5; ! Note that every INPUT must end with a semicolon (;); ? x>0; ? y>0; ? end ! END statement will terminate the model; :go ! GO command will solve the model; ROWS= 4 VARS= 2 NO. INTEGER VARS= 0 ( ALL ARE LINEAR) NONZEROES= 7 CONSTRAINT NONZ= 4( 4 ARE +- 1) DENSITY= .583 SMALLEST AND LARGEST ELEMENTS IN ABSOLUTE VALUE= 1.00000 5.00000 NO. < : 0 NO. =: 0 NO. > : 3, OBJ=MIN, GUBS <= 2 SINGLE COLS= 0 MAJOR STEP= 1 SUM INF.= 5.00000 OBJ.= 10.0000 MAJOR STEP= 1 SUM INF.= .000000E+00 OBJ.= 10.0000 MAJOR STEP= 1 SUM INF.= .000000E+00 OBJ.= 10.0000 OPTIMUM FOUND AT STEP 1 SOLUTION OBJECTIVE VALUE = 10.00 VARIABLE VALUE REDUCED COST X 5.000000 .0000000E+00 Y .0000000E+00 1.000000 ROW SLACK OR SURPLUS DUAL PRICE 1 10.00000 1.000000 2 .0000000E+00 -2.000000 3 -5.000000 .0000000E+00 4 .0000000E+00 .0000000E+00 : ! If the meaning of this is unclear, talk to your instructor!; : look all ! The current model can be displayed with the LOOK commanl; MODEL: 1) MIN= 2 * X + 3 * Y ; 2) X + Y > 5 ; 3) X > 0 ; 4) Y > 0 ; END : del 4 ! DEL will delete the fourth row of current model; : look 2 3 ! You can specify a particular range to LOOK at; 2) X + Y > 5 ; 3) X > 0 ; : ext ! EXT will extend the current model; ? y > 0; ! You can experiment the new input. Here the deleted; ? end ! row is recovered. END will terminate the model input; : save ! This command asks to save the current model in a file; ! Lingo asks you to provide a file name; FILE NAME= save.out ! This is an arbitrary file name; ! The filename may be included with the save command; : save foo.bar : take save.out ! TAKE command can retrieve the model saved by SAVE; ! Command files may also be created with an editor; : look all ! Use LOOK ALL command to check the content of save.out; MODEL: 1) MIN= 2 * X + 3 * Y ; 2) X + Y > 5 ; 3) X > 0 ; 4) Y > 0 ; END
From the previous screens, a few of the fundamental Lingo commands are introduced. However, there are still more commands for general use. To get a list of available command, you need to type COMMANDS at the Lingo prompt. To get help for a specific command, you need to type HELP LOOK at the system colon prompt, where LOOK can be replaced by any command that you need help with.