CDE

Task/Dynamic-variable-names/0DESCRIPTION

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+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.
+
+;See also
+* [[Eval in environment]] is a similar task.

Task/Dynamic-variable-names/1META.yaml

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+---
+note: Programming environment operations

Task/Dynamic-variable-names/AutoHotkey/dynamic-variable-names.ahk

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+InputBox, Dynamic, Variable Name
+%Dynamic% = hello
+ListVars
+MsgBox % %dynamic%  ; says hello

Task/Dynamic-variable-names/BASIC/dynamic-variable-names.bas

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+10 INPUT "Enter a variable name", v$
+20 KEYIN "LET "+v$+"=42"

Task/Dynamic-variable-names/BBC-BASIC/dynamic-variable-names.bbc

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+      INPUT "Enter a variable name: " name$
+      INPUT "Enter a numeric value: " numeric$
+      dummy% = EVAL("FNassign("+name$+","+numeric$+")")
+      PRINT "Variable " name$ " now has the value "; EVAL(name$)
+      END
+
+      DEF FNassign(RETURN n, v) : n = v : = 0

Task/Dynamic-variable-names/Batch-File/dynamic-variable-names.bat

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+@echo off
+setlocal enableDelayedExpansion
+
+set /p "name=Enter a variable name: "
+set /p "value=Enter a value: "
+
+::Create the variable and set its value
+set "%name%=%value%"
+
+::Display the value without delayed expansion
+call echo %name%=%%%name%%%
+
+::Display the value using delayed expansion
+echo %name%=!%name%!

Task/Dynamic-variable-names/Bracmat/dynamic-variable-names.bracmat

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+( put$"Enter a variable name: "
+& get$:?name
+&   whl
+  ' ( put$"Enter a numeric value: "
+    & get$:?numeric:~#
+    )
+& !numeric:?!name
+& put$(str$("Variable " !name " now has the value " !!name \n))
+);

Task/Dynamic-variable-names/Clojure/dynamic-variable-names.clj

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+(eval `(def ~(symbol (read)) 42))

Task/Dynamic-variable-names/Common-Lisp/dynamic-variable-names-1.lisp

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+(defun rc-create-variable (name initial-value)
+  "Create a global variable whose name is NAME in the current package and which is bound to INITIAL-VALUE."
+  (let ((symbol (intern name)))
+    (proclaim `(special ,symbol))
+    (setf (symbol-value symbol) initial-value)
+    symbol))

Task/Dynamic-variable-names/Common-Lisp/dynamic-variable-names-2.lisp

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+CL-USER> (rc-create-variable "GREETING" "hello")
+GREETING
+
+CL-USER> (print greeting)
+"hello"

Task/Dynamic-variable-names/E/dynamic-variable-names.e

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+def makeNounExpr := <elang:evm.makeNounExpr>
+
+def dynVarName(name) {
+    def variable := makeNounExpr(null, name, null)
+
+    return e`{
+
+        def a := 1
+        def b := 2
+        def c := 3
+
+        {
+            def $variable := "BOO!"
+            [a, b, c]
+        }
+
+    }`.eval(safeScope)
+}
+
+? dynVarName("foo")
+# value: [1, 2, 3]
+
+? dynVarName("b")
+# value: [1, "BOO!", 3]
+
+? dynVarName("c")
+# value: [1, 2, "BOO!"]

Task/Dynamic-variable-names/Forth/dynamic-variable-names.fth

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+s" VARIABLE " pad swap move
+." Variable name: " pad 9 + 80 accept
+pad swap 9 + evaluate

Task/Dynamic-variable-names/Haskell/dynamic-variable-names.hs

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+data Var a = Var String a deriving Show
+main = do
+    putStrLn "please enter you variable name"
+    vName <- getLine
+    let var = Var vName 42
+    putStrLn $ "this is your variable: " ++ show var

Task/Dynamic-variable-names/JavaScript/dynamic-variable-names.js

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+var varname = 'foo';  // pretend a user input that
+var value = 42;
+eval('var ' + varname + '=' + value);

Task/Dynamic-variable-names/Lua/dynamic-variable-names.lua

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+_G[io.read()] = 5 --puts 5 in a global variable named by the user

Task/Dynamic-variable-names/PHP/dynamic-variable-names.php

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+<?php
+$varname = rtrim(fgets(STDIN)); # type in "foo" on standard input
+$$varname = 42;
+echo "$foo\n"; # prints "42"
+?>

Task/Dynamic-variable-names/Perl/dynamic-variable-names-1.pl

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+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"

Task/Dynamic-variable-names/Perl/dynamic-variable-names-2.pl

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+use strict;
+
+print "Enter a variable name: ";
+my $foo;
+my $varname = <STDIN>; # type in "foo" on standard input
+chomp($varname);
+my $varref = eval('\$' . $varname);
+$$varref = 42;
+print "$foo\n"; # prints "42"

Task/Dynamic-variable-names/PicoLisp/dynamic-variable-names.l

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+(de userVariable ()
+   (prin "Enter a variable name: ")
+   (let Var (line T)                                  # Read transient symbol
+      (prin "Enter a value: ")
+      (set Var (read))                                # Set symbol's value
+      (println 'Variable Var 'Value (val Var)) ) )    # Print them

Task/Dynamic-variable-names/Python/dynamic-variable-names-1.py

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+>>> name = raw_input("Enter a variable name: ")
+Enter a variable name: X
+>>> globals()[name] = 42
+>>> X
+42

Task/Dynamic-variable-names/Python/dynamic-variable-names-2.py

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+>>> name = input("Enter a variable name: ")
+Enter a variable name: X
+>>> globals()[name] = 42
+>>> X
+42

Task/Dynamic-variable-names/R/dynamic-variable-names.r

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+# Read the name in from a command prompt
+varname <- readline("Please name your variable >")
+# Make sure the name is valid for a variable
+varname <- make.names(varname)
+message(paste("The variable being assigned is '", varname, "'"))
+# Assign the variable (with value 42) into the user workspace (global environment)
+assign(varname, 42)
+#Check that the value has been assigned ok
+ls(pattern=varname)
+get(varname)

Task/Dynamic-variable-names/REXX/dynamic-variable-names.rexx

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+/*REXX program to show use of  dynamic variable names.                  */
+
+parse arg new value
+say 'Arguments as they were entered via the command line =' new value
+say
+call value new,value
+say 'The newly assigned value (as per the VALUE bif)------' new value(new)

Task/Dynamic-variable-names/Ruby/dynamic-variable-names.rb

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+p "Enter a variable name"
+x = gets.chomp!
+instance_variable_set "@" + x, 42
+p "The value of #{x} is #{instance_variable_get "@" + x}"

Task/Dynamic-variable-names/Scheme/dynamic-variable-names.ss

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+=> (define (create-variable name initial-val)
+     (eval `(define ,name ,initial-val) (interaction-environment)))
+
+=> (create-variable (read) 50)
+<hello
+
+=> hello
+50

Task/Dynamic-variable-names/Smalltalk/dynamic-variable-names.st

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+| varName |
+varName := FillInTheBlankMorph
+	request: 'Enter a variable name'.
+Compiler
+	evaluate: '| ', varName, ' | ', varName, ' := 42.
+	Transcript
+		show: ''value of ', varName, ''';
+		show: '' is '';
+		show: ', varName.

Task/Dynamic-variable-names/Tcl/dynamic-variable-names-1.tcl

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+puts "Enter a variable name:"
+gets stdin varname
+set $varname 42
+puts "I have set variable $varname to [set $varname]"

Task/Dynamic-variable-names/Tcl/dynamic-variable-names-2.tcl

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+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)"

Task/Dynamic-variable-names/Tcl/dynamic-variable-names-3.tcl

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+puts -nonewline "Enter a variable name: "; flush stdout
+gets stdin varname
+upvar 0 $varname v; # The ‘0’ for “current scope”
+set v [expr int(rand()*100)]
+puts "I have set variable $varname to $v (see for yourself: [set $varname])"