On 11/16/17, Cecil Westerhof <cldwester...@gmail.com> wrote:
> puts $Tea, $Location
Everything in TCL is a function. The syntax is "FUNCTIONNAME ARG1
ARG2 ARG3 ..." where the arguments are separated by white space. The
"puts" function takes either one or two arguments. The one-argument
form of "puts" outputs ARG1 to standard-output. The two-argument form
of "puts" sends ARG2 to output stream specified by ARG1.
Your code above tries to invoke the two-argument form of "puts".
Equivalent javascript code would be:
puts(Tea + ",", Location)
The error arises because there is no output channel named by the
result of Tea+",". What you want is the one-argument form, equivalent
to this JS:
puts(Tea + ", " + Location)
To get that using TCL syntax, you can use quoting to make the two
separate arguments into one:
puts "$Tea, $Location"
The key point is that everything in TCL is of the format FUNCTION ARG1
ARG2 .... The processing steps are like this:
(1) Identify arguments separated by whitespace. Note that all text
within "..." and within nested {...} is a single argument.
(2) Resolve quotes. This means remove the outermost {...} from
arguments quoted using {...}. Remove the "..." around double-quoted
argments, and also resolve any $variable name within the double
quotes. The $variable name resolution does not happen with {...}
(3) Invoke the function with its arguments.
Note that *everything* is a function. Even "control" statements. In
Tcl when you see:
if {$i<10} {
puts "yes"
} else {
puts "no"
}
That really is invoking the "if" function with 4 arguments. Since
everything is a function, everything follows exactly the same quoting
rules. This is an important feature of Tcl that programmers whose
prior experience has been exclusively using Algol-derived languages
such as C, Java, Javascript, and Python may have difficulty getting
their heads around. But once you do "get it", it starts to seem very
natural.
--
D. Richard Hipp
d...@sqlite.org
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