Version 25 of HelloWorld

if 0 {

Introduction

MiHa 2015-06-13: HelloWorld-programs are supposed to be the most simple, working programs of a given language.

But I want to extend such a HelloWorld-program to a one-page - reference-card,
where all the essential features of the language are shown.
Several short programs would be ok, too.
If possible, while doing something useful (and/or funny).

Tcl by itself (without Tk) is quite simple , so an amount of code to fill about one printed page should be enough.
(The layout may need to be tweaked, e.g. printing front and back, landscape, and in 2-4 columns:)

Basic Tcl Commands to cover:

Comments / statements
Output: puts / -nonewline
- format
Numeric variables: set
multiple statements / assignments in one line
- simple calculations: incr / expr
proc / return - for functions
basic flowcontrol:
- if / then / else / elseif / comparing
- for - loop, maybe also the while-loop / break / continue
foreach
String variables / quoting
exit

Advanced features (to include if space permits):

input: gets, eof, scan / checking the input
This is an important topic, but likely too much for one page.
catch
global / $::var
string-operations (e.g. find/extract/replace char in a string, append, delete/split ...)
data structures:
- array / parray
- list / lassign, lappend, lset, linsert, lreplace / lindex, llength / lrange, lsearch, lsort
- dict
file-operations / open, close / glob

...

More features, to be left out, for a later lesson (too advanced, or too rarely needed for an introduction):

upvar / uplevel
namespaces
eval
interp
lambda
regexp - this is very likely too complex to cover as just one small example on a general introduction page.
switch
unknown

...

Things to be aware of:

comments are commands, so quotes and braces inside need to be balanced
when to use / not to use "$" with variablenames ( set i 1; puts $i; incr i $i )

Maybe there already are some programs here in the wiki that would qualify for such a refcard-program...

}

Program 1 - puts

  # HelloWorld001.tcl - 2015-06-13 - http://wiki.tcl.tk/41268

  # Output a string to terminal:

  puts "Hello, World!"

  ### END ###

Program 2 - set, incr

# HelloWorld002 - 2015-06-23
# http://ideone.com/9KlN4c

# Assign value to variables, and output:

set a "The answer is"
set n 42

puts $a
puts $n

incr n                ;# add 1 to a numeric variable
puts "$a now $n"

# END #

Output 2

The answer is
42
The answer is now 43

Program 3 - clock, timedate, if, else

# HelloWorld003.tcl - MiHa - 2015-06-13
# http://wiki.tcl.tk/41268 / http://ideone.com/xl0IBI

# Query the time (cs as a number, td and hh as a string), 
# output depending on the value of the hour:

set cs [clock seconds]                                    ;# seconds since 1970-01-01
set td [clock format $cs  -format "%Y-%m-%d  %H:%M:%S" ]  ;# timedate
set hh [clock format $cs  -format %H ]                    ;# hours (00-23)

puts "cs=$cs  td='$td'  hh=$hh"

if { $hh < "12" } {
    puts -nonewline "Good morning, "
} else {
    puts -nonewline "Hello, "
}
puts "World!"

# END #

Output 3

cs=1434926575  td='2015-06-21  22:42:55'  hh=22
Hello, World!

Program 4 - clock, if,else,elseif

# HelloWorld004.tcl - MiHa - 2015-06-21
# http://wiki.tcl.tk/41268 / http://ideone.com/Llp8Os

# Query the hour from the clock, 
# output text depending on the value of the hour:

set cs [clock seconds]                          ;# seconds since 1970-01-01
set hh [clock format $cs  -format %H ]          ;# hours (00-23)

puts "cs=$cs  hh=$hh"

if { $hh < "12" } {
    puts -nonewline "Good morning, "
} elseif { $hh > "18" } {
    puts -nonewline "Good evening, "
} else {
    puts -nonewline "Hello, "
}
puts "World!"

# END #

Output 4

cs=973531773  hh=17
Hello, World!

and

cs=1434927642  hh=23
Good evening, World!

Program 5 - string compare

# HelloWorld005 - 2015-06-23
# http://ideone.com/OJoort

# Comparing strings:

set hh "20"

set tx "Hello"
if { $hh < "12" } { set tx "Good Morning" }
if { $hh > "18" } { set tx "Good Evening" }

puts "It is $hh:00 --> $tx, World !"
#.

Output 5

It is 20:00 --> Good Evening, World !

Program 6 - proc,return

# HelloWorld006 - 2015-06-23
# http://ideone.com/GBiMab

# Comparing strings, proc as function

proc greeting {hh}  {
  set gr "Hello"
  if { $hh <  "12" } { set gr "Good Morning"    }
  if { $hh == "12" } { set gr "Happy Lunchtime" }
  if { $hh  > "18" } { set gr "Good Evening"    }
  return $gr
}

set hh "12"
set tx [greeting $hh]
puts "It is $hh:00 --> $tx, World !"

#.

Output 6

It is 12:00 --> Happy Lunchtime, World !

Program 7 - while, gets

# HelloWorld007 - 2015-06-23
# http://ideone.com/mcV6YL

# Comparing strings, proc as function, input in while-loop

proc greeting {hh}  {
# This proc returns a result as soon as a match is found:
  set gr "Hello"
  if { $hh <  "12" } { return "Good Morning"    }
  if { $hh == "12" } { return "Happy Lunchtime" }
  if { $hh  > "24" } { return "Goodbye" }
  if { $hh  > "18" } { return "Good Evening"    }
  return $gr
}

set hour "99"               ;# start with any value that keeps the loop going
while { $hour > "0" } {
  puts -nonewline "Enter hour, 0 to quit: "
  set hour [gets stdin]
  puts $hour
  
  puts "It is $hour:00 --> [greeting $hour], World !"
}
puts "Bye!"

#.

Output 7

Enter hour, 0 to quit: 1
It is 1:00 --> Good Morning, World !
Enter hour, 0 to quit: 11
It is 11:00 --> Good Morning, World !
Enter hour, 0 to quit: 12
It is 12:00 --> Happy Lunchtime, World !
Enter hour, 0 to quit: 15
It is 15:00 --> Hello, World !
Enter hour, 0 to quit: 17
It is 17:00 --> Hello, World !
Enter hour, 0 to quit: 18
It is 18:00 --> Hello, World !
Enter hour, 0 to quit: 19
It is 19:00 --> Good Evening, World !
Enter hour, 0 to quit: 25
It is 25:00 --> Goodbye, World !
Enter hour, 0 to quit: 0
It is 0:00 --> Good Morning, World !
Bye!

Program 8 - for, format

# HelloWorld008 - 2015-06-23
# http://ideone.com/lKo08L

# Comparing strings, proc as function, for-loop, format

proc greeting {hh}  {
# This proc returns a result as soon as a match is found:
  set gr "Hello"
  if { $hh <  "12" } { return "Good Morning"    }
  if { $hh == "12" } { return "Happy Lunchtime" }
  if { $hh  > "24" } { return "Goodbye" }
  if { $hh  > "18" } { return "Good Evening"    }
  return $gr
}

puts "Greeting:"
for {set h 0} {$h<=25} {incr h} {
 #set hour $h                  ;# Tcl converts number to string, as needed
 #set hour [format "%2d"  $h]  ;# format as numeric string with 2 digits
  set hour [format "%02d" $h]  ;# format as 2 digits with leading 0
  puts "at $hour:00 --> [greeting $hour], World !"
}
puts "Done."

#.

Output 8

Greeting:
at 00:00 --> Good Morning, World !
at 01:00 --> Good Morning, World !
at 02:00 --> Good Morning, World !
at 03:00 --> Good Morning, World !
at 04:00 --> Good Morning, World !
at 05:00 --> Good Morning, World !
at 06:00 --> Good Morning, World !
at 07:00 --> Good Morning, World !
at 08:00 --> Good Morning, World !
at 09:00 --> Good Morning, World !
at 10:00 --> Good Morning, World !
at 11:00 --> Good Morning, World !
at 12:00 --> Happy Lunchtime, World !
at 13:00 --> Hello, World !
at 14:00 --> Hello, World !
at 15:00 --> Hello, World !
at 16:00 --> Hello, World !
at 17:00 --> Hello, World !
at 18:00 --> Hello, World !
at 19:00 --> Good Evening, World !
at 20:00 --> Good Evening, World !
at 21:00 --> Good Evening, World !
at 22:00 --> Good Evening, World !
at 23:00 --> Good Evening, World !
at 24:00 --> Good Evening, World !
at 25:00 --> Goodbye, World !
Done.

Program 9 - expr, format

# HelloWorld009.tcl - 2015-06-23
# http://ideone.com/kgfFX1

# calculations using expr, formatting numbers

  set x 3.0
  set y 7.0

  set distance [expr sqrt($x * $x + $y * $y)]
  set dist2    [format %9.2f $distance]        ;# format as float with 2 digits
  
  puts "x=$x y=$y  distance=$distance ==> $dist2"

#.

Output 9

x=3.0 y=7.0  distance=7.615773105863909 ==>      7.62

Program 10

# HelloWorld010.tcl - 2015-06-23

#.

Output 10

xx

Some ideas:

Table of primes
Dice-rolling
- with min/max/average
Calculate distance
Number of days between dates

...

 **Program 1x**

# HelloWorld00x.tcl - 2015-06-23

#.

 ***Output 1x***

xx

Remarks

This is the Alpha-version, there will be bugs, so use with caution
...

See also:

ClockDemo
...

Category Example

Category Tutorial