#Upvar command ties (make an alias)the name of a variable in the current 
#scope to a variable in diffrent scope
#this is commonly used to simulate pass by refrence to procs
#1 using return
proc proc_by_copy { a b c } {
  return  [expr $a*2]
  return  [expr $b*2]
  return  [expr $c*2]
  }
set l [proc_by_copy 2 3 4]
puts "$l"
#2 using set(copy by value)(copied the values but not modified it)
proc proc_by_copy { a b c } {
  set a [expr $a*2]
  set b [expr $b*2]
  set c [expr $c*2]
  puts "new values are $a $b $c"
 }
set l [proc_by_copy 2 3 4 ]
#proc_by_copy $a $b $c
#3 Using Upvar (copy by refrence)(taking their address)
#proc proc_by_refrence { a b c } {
 # upvar $a a_
 # upvar $b b_
  #upvar $c c_
  #set a_  [expr $a_*2]
  #set b_  [expr $b_*2]
  #set c_  [expr $c_*2]
  #puts "new values are $a $b $c"
#}
#proc printbyname { varname } {
 # upvar $varname var
  #puts  stdout " $varname = $var "
#}
#printbyname x
#set x 10
puts "what is your name ?"
set answer [gets stdin]
puts "$answer"
by

Tool Command Language(TCL) online compiler

Write, Run & Share TCL code online using OneCompiler's TCL online compiler for free. It's one of the robust, feature-rich online compilers for TCL language, running the latest TCL version 8.6. Getting started with the OneCompiler's TCL editor is easy and fast. The editor shows sample boilerplate code when you choose language as TCL and start coding.

Taking inputs (stdin)

OneCompiler's TCL online editor supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample TCL program which takes name as input and prints hello message with your name.

set name [gets stdin]
puts "Hello $name"

About TCL

Tool Command Language(TCL) is a general purpose scripting language which is commonly used for GUIs and for testing. Everything is by default string in TCL. It was created by John Osterhout in 1989.

Syntax help

Variables

Variable is a identifier which is used to hold the value. set is used to create variables.

Examples

set name onecompiler

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition IF-ELSE is used.

if(conditional-expression) {
   #code
} else {
   #code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression) {    
value1 {     
 # code
}    
value1 {     
 # code
}    
...
default {
# code
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for{start}{test}{next}{  
  # code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 # code 
}

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

set ArrayName(Index) value

Procedures

Procedure is a sub-routine which contains set of statements. Uusually procedures are required when multiple calls are made to same set of statements. Procedures increases re-usuability and modularity.

Syntax

proc procedureName {arguments} {
   # code
}