fb_system()

[txt, OK]: fb_system(names, sys, emv, hint)

• names list from the names input field
• sys list of indices of elements which belong to the system (to be active)
• env list of indices of elements which belong to the environment and have to be deactivated and replaced by reactions
• hint text, problem-specific hint if the system boundaries aren't correct.

Templates

Question text

[[feedback:System]]

Feedback variables

obj: stackjson_parse(objects);
[txt, OK]: fb_reactions(obj, 3, 1);

Feedback:

Field	Value
sans	OK
tans	true
feedback true	{@txt@}
feedback false	{@txt@}

Activation/Deactivation

names[n]="show" is true if element with index n is activated and false if not.

This can be used to check if all supports or distributed loads are de-activated.

The following snippet from the Feedback variables sets OK to true if the object with number i_beam are activated and the objects i_S1, i_S2 and i_S3 are not.

i_beam: 2; i_S1: 5; i_S2: 6; i_S3: 7; 
OK: is(
  names[i_S1]   # "show" and 
  names[i_S2]   # "show" and 
  names[i_S3]   # "show" and 
  names[i_beam] = "show");
txt: if OK then " Die Systemgrenzen stimmen." 
  else " Die Systemgrenzen stimmen nicht. Nur der Balken gehört zum System. Mindestens die Stäbe müssen entfernt (deaktiviert) werden.";

Use AlgEquiv question test with OK as sans and true as tans.

In both branches, say

{@txt@}