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serial-porttcldts

expected boolean value error in tcl and arrays

I've slowly progressing through my serialport tcl app but hit another wall.

I want to create an array of boolean values to iterate in a for loop.

In the for loop, DTR will send a serial output.

Below I have the following code:

set rs232 [open COM3: r]
fconfigure $rs232 -ttycontrol {DTR 0}

array set values {
0   0
1   1
}

set n [array size values]

set x 0
for {set a 0} {$a <=15} {incr a} {
fconfigure $rs232 -ttycontrol {DTR $values(0)}
wait 1000
fconfigure $rs232 -ttycontrol {DTR $values(1)}
wait 1000
}

I run it and I get the error:

    expected boolean value but got "$values(0)"

Can anyone tell me why this is and how do I fix it?

Solution

  • This invocation:

    fconfigure $rs232 -ttycontrol {DTR $values(0)}

    passes the value "DTR $values(0)" for -ttycontrol to fconfigure. The invocation

    fconfigure $rs232 -ttycontrol [list DTR $values(0)]

    passes "DTR 0".

    The braces prevent substitution of the variable, but the invocation of list enforces it.

    Alternatively, you could use one of

    fconfigure $rs232 -ttycontrol "DTR $values(0)"
fconfigure $rs232 -ttycontrol [subst {DTR $values(0)}]