Dynamic variable names
You are encouraged to solve this task according to the task description, using any language you may know.
Create a variable with a user-defined name. The variable name should not be written in the program text, but should be taken from the user dynamically.
AutoHotkey
<lang AutoHotkey> InputBox, Dynamic, Variable Name %Dynamic% = hello ListVars MsgBox % %dynamic% ; says hello </lang>
Common Lisp
<lang lisp>(defmacro set-string (string value)
`(setf ,(read-from-string string) ,value))
(set-string "dynamicA" "hello") (print dynamicA)</lang>
Forth
<lang forth>s" VARIABLE " pad swap move ." Variable name: " pad 9 + 80 accept pad swap 9 + evaluate</lang> Of course, it is easier for the user to simply type VARIABLE name at the Forth console.
Perl
<lang perl>print "Enter a variable name: "; $varname = <STDIN>; # type in "foo" on standard input chomp($varname); $$varname = 42; # when you try to dereference a string, it will be
# treated as a "symbolic reference", where they
# take the string as the name of the variable
print "$foo\n"; # prints "42"</lang>
PHP
<lang php><?php $varname = rtrim(fgets(STDIN)); # type in "foo" on standard input $$varname = 42; echo "$foo\n"; # prints "42" ?></lang>
Python
<lang python>>>> n = raw_input("Enter a variable name: ") Enter a variable name: X >>> exec n + " = 42" >>> X 42</lang>
<lang python>>>> n = input("Enter a variable name: ") Enter a variable name: X >>> exec(n + " = 42") >>> X 42</lang>
Tcl
<lang Tcl>puts "Enter a variable name:" gets stdin varname set $varname 0</lang> Note that it is more normal to use the user's name to index into a Tcl associative array, as the syntax gets easier to work with in that case: <lang tcl>puts -nonewline "Enter an element name: "; flush stdout gets stdin elemname set ary($elemname) [expr int(rand()*100)] puts "I have set element $elemname to $ary($elemname)"</lang>