TCL array substitution

Question

In TCL (running v8.6.6) I want to create an array with a substitution of one or more of the value of the array with the value of another variable.

If we were in C I will write

float a = 10;
float b[4] = {1.0, 2.0, 3.0, 4.0};
b[2]=a;

and if I print on stdout I got 1.0 10.0 3.3 4.0.

In TCL instead I started by a simple exampe. I wrote

set a 10.0
set b $a

puts $b

I got 10.0 as output, but if I want to do the same in a array so I wrote

set a 10.0
set b {1.0 $a 3.0 4.0}

puts $b

and I'm expecting

1.0 10.0 3.0 4.0

but I got

-0.5 $a 0.5 0.79

Any idea?

Thanks a lot

C indexes from zero (just like Tcl); printing that array should have given 1.0 2.0 10.0 4.0 — Donal Fellows
– Donal Fellows, Commented Jul 9, 2020 at 14:18
Terminology: An array in TCL is, like in awk, an associative array/hash table. You're working with a list, which is more like a C array. — Shawn
– Shawn, Commented Jul 9, 2020 at 20:44
And what you should be seeing printed by that tcl code is 1.0 $a 3.0 4.0. What you say your C code prints is different from what should be seen too, though, so there's got to be more going on that you didn't share in the question. — Shawn
– Shawn, Commented Jul 9, 2020 at 21:08

Colin Macleod · Accepted Answer · 2020-07-09 12:34:02Z

2

Curly brackets {} prevent substitution, try:

set b [list 1.0 $a 3.0 4.0]

answered Jul 9, 2020 at 12:34

Colin Macleod

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Donal Fellows · Accepted Answer · 2020-07-09 14:15:30Z

0

Though you've found that creating a list with substitutions is done via the list command, here's how to do the assignment to an element that is equivalent to b[2]=a; from C.

lset b 2 $a

answered Jul 9, 2020 at 14:15

Donal Fellows

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1 Comment

Donal Fellows Over a year ago

This is technically not the answer to what you asked, but it does show what you might've been thinking about.

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