- The binary format command allows you to convert a number into a character (or more generally, a binary string). The advantage of this first method is that you can easily create strings with characters that can not be found directly on the keyboard.
- By selecting characters at random from a given string you can control both which characters you get in the output and their relative frequency (by duplicating characters that should appear more often).

*If you have an interesting method (for instance indeed Markov chains), then please add them!*

# # Proc to generate a string of (binary) characters # Range defaults to 'A'-'z' (this includes several non-alphabetic # characters) # binary scan A c A binary scan z c z proc randomDelimString [list length [list min $A] [list max $z]] { set range [expr {$max-$min}] set txt "" for {set i 0} {$i < $length} {incr i} { set ch [expr {$min+int(rand()*$range)}] append txt [binary format c $ch] } return $txt } # # Proc to generate a string of (given) characters # Range defaults to "ABCDEF...wxyz' # proc randomRangeString {length {chars "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"}} { set range [expr {[string length $chars]-1}] set txt "" for {set i 0} {$i < $length} {incr i} { set pos [expr {int(rand()*$range)}] append txt [string range $chars $pos $pos] } return $txt } puts [randomDelimString 30] puts [randomRangeString 30] puts [randomRangeString 30 "aaabcdeeeeee"] # # Time the performance # puts [time {set x [randomDelimString 100]} 10000] puts [time {set x [randomRangeString 100]} 10000] if { 0 } { # Sample output (Pentium II, 350 MHz, running Windows 98, Tcl 8.3.4): [lmZQAiB]Hb_hFpEw`LiEQSjOSsBfC BnnWCymqGYaFyAKOAMPfmnYKRJTugu abcbdeaeeadeeeceaebaaebeeeebee 3564 microseconds per iteration 2862 microseconds per iteration }

In the chatroom, RS came up with the following solution:

proc lpick L {lindex $L [expr {int(rand()*[llength $L])}]} proc randomlyPicked { length {chars {C G T A}} } { for {set i 0} {$i<$length} {incr i} {append res [lpick $chars]} return $res } puts [randomlyPicked 30]

Stu 2007-02-14 The CAS extension also provides random char/string commands.

The random page also has a random string generator.

Stu 2007-10-23 Random A-Za-z one-liner:

proc randAZazStr {len} { return [subst [string repeat {[format %c [expr {int(rand() * 26) + (rand() > .5 ? 97 : 65)}]]} $len]] }aspect 2014-12: this previously had int(rand() * 10) > 5, which is a long-winded and incorrect way to flip coins (it's true only 40% of the time). A caution to those careless with entropy!