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[REBOL] problems with local vars??? Re:

From: bhandley:zip:au at: 16-Aug-2000 23:19

Hi Raimund, The first thing is to understand that you can use my-local-string like a variable, but it is not really a variable (in the sense of a pointer to memory). It is a word that can refer to a value. The word my-local-string exists in it's own right - so does the value of type string "that is local". Doing an "assignment" associates the two. With this in mind, Rebol does not "initialise" the variable - it actually associates a word with a value. In C and other compiled languages when you declare a variable you give the variable a datatype and when you assign something to the variable your value is just a bunch of bits that conform to the datatype. This is not the case with Rebol. In Rebol the value has the type information. A word is a value too - a special type of value that can be associated with another value. In Rebol everything is a value including functions. So local-func is a word that refers to a value of type function. Here's your function slightly edited local-func: function [input][my-local-string][ my-local-string: ; This says make it so that my-local-string refers to the next value. (1) "that is local " ; This says create a string value. (2) print append my-local-string input ; (3) ] Both (1) and (2) are part of the function definition. When (3) is actually executed, it in fact changes the value of (2). Why? because when the line is evaluated, my-local-string is evaluted before the append. My local string evaluates to the actual string stored in the function definition. You can see how the function definition has changed by calling your function once and then using the command. source local-func Now, if you function read like this... local-func2: function [input][my-local-string][ my-local-string: ; This says make it so that my-local-string refers to the next value. (4) copy "that is local " ; This says create a new string value that is a copy of another. (5) print append my-local-string input ; (6) ] What would happen in (5) is a copy would be make of the string that is stored inside the function definition and the copy would be "assigned" to the word my-local-string. In this case when line (6) is executed the string will change but the function will not because the function does not refer to the copy. Hope it helps. Brett.