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language:state [2020-06-15 12:53 SLT] sei Improve some wording. |
language:state [2020-06-15 12:58 SLT] (current) sei more wording |
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| where `<state_name`> can be $kw[default] or the name of any existing state. This statement causes a state switch, interrupting execution of the current function or event. | where `<state_name`> can be $kw[default] or the name of any existing state. This statement causes a state switch, interrupting execution of the current function or event. | ||
| - | When a state switch statement is found, a $kw[return] statement is automatically inserted at that point in the code, and when the currently executed event finalizes, if the state is NOT the current state, the state switch happens. This triggers two events: first, the $lev[state_exit] event for this state; then, the $lev[state_entry] event for the state changed to. | + | When a state switch statement is found, a $kw[return] statement is automatically inserted at that point in the code, and when the current event finalizes, if the state is NOT the current state, the state switch happens. This triggers two events: first, the $lev[state_exit] event for this state; then, the $lev[state_entry] event for the state changed to. |
| A state switch statement that specifies the same state where it is executed, causes the interruption of the current event or function, but does not cause any other effects: neither the $ev[state_exit] nor the $ev[state_entry] events of the current state are executed. | A state switch statement that specifies the same state where it is executed, causes the interruption of the current event or function, but does not cause any other effects: neither the $ev[state_exit] nor the $ev[state_entry] events of the current state are executed. | ||
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| ===== Hacks ===== | ===== Hacks ===== | ||
| - | State switches are designed to be used only within event declarations. They work by flagging the state change and adding a $lkw[return] statement at the point where the state switch statement is. The flag is checked when the currently executed event terminates. That creates the illusion that the state switch acts as an immediate jump to another state, stopping execution of the current code. | + | State switches are designed to be used only within event declarations. They work by signalling the state change and adding a $lkw[return] statement at the point where the state switch statement is. The signal is checked when the current event terminates. That creates the illusion that the state switch acts as an immediate jump to another state, stopping execution of the current code. |
| - | This $kw[return] trick, however, does not work in user-defined functions, because it would return to the caller, rather that completely interrupting the currently running event. Since it doesn't work in these circumstances, it can't be properly supported in UDFs easily, and rather than doing something more complex, LL chose to not support it in UDFs at all, and implemented a check to ensure that there is no state switch statement within a user function. | + | This $kw[return] trick, however, does not work in user-defined functions, because it would return to the caller, rather that completely interrupting the currently running event. Since it doesn't work in these circumstances, it can't be properly supported in UDFs easily, and rather than adding the necessary complexity for adding proper support for it, LL chose to not support it in UDFs at all, and implemented a check in the compiler to ensure that there is no state switch statement within a user function. |
| However, due to a bug, the check fails when the statement is somewhere within the block associated to: | However, due to a bug, the check fails when the statement is somewhere within the block associated to: | ||