MODELS > Examples > Models Controls

The MODELS language supports four types of control structures

1. IF

2. FOR

3. DO

4. WHILE

1. if - then - else - elseif - endif

This example illustrates how to used the IF structure in MODELS.

MODEL if_example

VAR k

INIT

k:=0

ENDINIT

EXEC

if k=0 then

k:=1

elsif k=1 then

write("In first 'elsif' with k=1")

k:=2

elsif k=2 then

write("In second 'elsif' with k=2")

k:=3

else

write("In 'else' with k=3")

endif

ENDEXEC

ENDMODEL

2. for - to - by - do - endfor

This example illustrated the usage of the FOR statement in MODELS.

MODEL for_example

VAR k

EXEC

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

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

FOR z10:=0 TO 5, 6, 7 TO 9 BY 1 -- 3 value groups: 0 to 5 : 0,1,2,3,4,5

-- 6 : 6

-- 7 to 9 by 1 : 7,8,9

FOR z1:=0 TO 8 BY 2 -- 1 group of values: 0,2,4,6,8

k:=z10*10 +z1 -- 0,2,4,6,8,10,12,14,16,18,20,22,24,...,94,96,98

write(k)

ENDFOR

FOR z10:=9 TO 0 by -1 -- 1 group of values: 9,8,7,6,5,4,3,2,1,0

FOR z1:=5, 0 -- 2 groups of single values (call it a list?): 5, 0

DO write(z10*10 +z1) -- 95,90,85,80,75,...,15,10,5,0

ENDFOR

FOR n:= 1 to 4

FOR m:= n to 4

DO write( m ) -- 1,2,3,4, 2,3,4, 3,4, 4

ENDFOR

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

ENDIF

ENDEXEC

ENDMODEL

Note!

The keyword DO is needed perform commands and must be concluded with ENDFOR. Nested FOR loops do not need DO-ENDFOR.

Standard syntax:

for i:=1 to 4 do

for j:=i to 4 do

x:=i*j

endfor

Simplified syntax:

for i:=1 to 4

for j:=i to 4 do

x:=i*j

endfor

3. do - redo - enddo

This example illustated the DO structure in MODELS.

MODEL do_example

VAR k

EXEC

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

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

k:=5

write('k=', k, ' in loop ')

k:=k-1

IF k>0 THEN REDO -- jump up to DO statement

ENDIF

ENDDO

write('k=', k, ' after loop ')

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

ENDIF

ENDEXEC

ENDMODEL

4. while - do - endwhile

This example illustrates the use of WHILE..ENDWHILE in MODELS.

MODEL while_example

VAR k

EXEC

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

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

k:=5

WHILE k>0 DO

write('k=', k, ' in loop ')

k:=k-1

ENDWHILE

write('k=', k, ' after loop ')

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

ENDIF

ENDEXEC

ENDMODEL