Common mistakes

Using `=` for strings

Use == for string equality:

# Wrong
arrival(sender | sender = "carol@example.net")

# Correct
arrival(sender | sender == "carol@example.net")

Use != for string disequality:

arrival(sender | sender != "blocked@example.net")

Using `==` for numbers

Use = for numeric equality:

# Wrong
arrival(sender, size | size == 10)

# Correct
arrival(sender, size | size = 10)

Use <> for numeric disequality:

# Wrong
arrival(sender, size | size != 10)

# Correct
arrival(sender, size | size <> 10)

Forgetting a signature

Every event name used in an expression needs a signature:

signature arrival {
    sender: string;
}

arrival(sender)

Forgetting the final expression

Named expressions are definitions, not the final monitored expression. End the file with the expression to monitor:

expr target {
    arrival(sender | sender == "carol@example.net")
}

target

Using `init` in the wrong mode

init is parsed by the syntax, but SyMon only supports initial constraints with parametric timing constraints. If SyMon reports that initial constraints are not supported, remove the init block or run the appropriate parametric timing mode. See Execution modes.

Mixing up `one_of` and `all_of`

one_of branches are separated by or:

one_of {
    arrival(sender | sender == "alice@example.com")
} or {
    arrival(sender | sender == "carol@example.net")
}

all_of branches are separated by and:

all_of {
    arrival(sender | sender == "alice@example.com")
} and {
    arrival(sender | sender != "blocked@example.net")
}

This is wrong:

one_of {
    arrival(sender | sender == "alice@example.com")
} and {
    arrival(sender | sender == "carol@example.net")
}

Trying to update event fields

Updates assign to global variables declared in var, not to fields declared in an event signature:

var {
    saved_sender: string;
}

signature arrival {
    sender: string;
}

arrival(sender | | saved_sender := sender)

Back to the Syntax overview, or continue with Syntax examples.

Common mistakes

Using = for strings

Using == for numbers