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1. Expressions

 

This example illustrates the use of expressions in MODELS

 

MODEL expr                      

 

CONST  c4 {val: 4}   -- constant with value of 4

 

VAR    a[1..6]       -- variables a[1], a[2], ... a[6]

      k             -- variable k

 

EXEC

IF t=timestep THEN       -- letting contents execute only at the first time step

write("*** Begin results of model 'expr' ***")

 k:=1               write("       1 : ", k)

 k:=2*k             write("       2 : ", k)

 k:=3-k             write("       1 : ", k)

 k:=3+k             write("       4 : ", k)

 k:=3/k             write("    0.75 : ", k)

        -- above, notice that all values are interpreted as real,

        -- even if they are expressed as integers

 k:=c4>3 AND c4=4   write("       1 : ", k)

        -- above, c4>3 is true, c4=4 is true, result is true

        -- notice that all logical values are expressed numerically (0 or 1)

 k:=-10 AND c4=4   write("       0 : ", k)

        -- above, -10 has logical value false because it is <=0

        -- notice cross-mapping of logical and numerical values

        -- -10 maps as false, c4=4 is true, false result maps as 0

 k:= -10 OR c4     write("       1 : ", k)

        -- above, -10 maps as false, c4 maps as true, true result maps as 1

 k:= k OR 0         write("       1 : ", k)

        -- above, k maps as true, 0 maps as false, true results maps as 1

 a[4]:=99           write("      99 : ", a[4])

 a[1..2]:=-a[4]     write("-99, -99 : ", a[1], ', ',a[2])

        -- above, multiple assignment of single value (see example arval.dat)

 a[3]:=NOT a[4]     write("       0 : ", a[3])

        -- above, a[4] maps as true, false result maps as 0

 k:=NOT a[1]       write("       1 : ", k)

        -- above, a[1] is -99 and maps as false, true result maps as 1

 k:=NOT k           write("       0 : ", k)

        -- above, k is 1 and maps as true, false result maps as 0

write("*** End results of model 'expr' ***")

ENDIF

ENDEXEC

ENDMODEL

 

 

 

2. Sums

 

This example illustrates sum() in MODELS

 

MODEL sum_example

CONST  c4 {val: 4}

VAR    a, b, k1, k2

INIT

 b:=2

ENDINIT

 

EXEC

 a:=t

 k1:=sum(c4| -t|a +t|b)                             -- = c4 -t*a +t*b

 k2:=sum(c4| -t|a +t|b) {min:-10.999 max:4.999}     -- same, with limits

ENDEXEC

ENDMODEL