Understanding the usage of braces

tcl

Solution

In a nutshell,

- Tcl's braces act like sh's single quotes -- group words (and lines) without interpolation.

- Tcl's double quotes act like sh's double quotes -- allowing interpolation.

The fact that you use curly braces in a `proc` definition is not mandatory. It's just the most convenient way to pass a script as an argument to proc without interpolating.

These are equivalent

proc add3 {a b c} {
    return [expr {$a + $b + $c}]
}

and

proc add3_weird [list a b c] "return \[expr {\[set a] + \[set b] + \[set c]}]"

Once you internalize Tcl quoting, you'll realize how truly flexible Tcl can be.

Problem

I'm learning Tcl/Tk and am confused on the usage of curly braces in tcl. To me it seems to be used to both indicate scope and declare strings! Is this a bug (or feature)? Is my interpretation correct?

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