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Index > Main > I can't address a variable given its name as a string?

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bougainville



Joined: 27 Mar 2006
Posts: 8
bougainville
I am trying to parse a simple string that says an arithmetic expression, and then evaluate the result.
I already have:
var1 dd 5
var2 dd6
The expression says to add the two existing variables. After parsing lets suppose I get the following:
sz1 dd 'var1'
sz2 dd 'var2'
sz3 dd '+'
Note that the string operands have the names of the variables that I want to add.
How can I obtain the values in var1 and var2 from the names written in sz1 and sz2?
Post 27 Mar 2006, 01:44
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shoorick



Joined: 25 Feb 2005
Posts: 1605
Location: Ukraine
shoorick
var1 is source label and does not binded with sz1 "var1" noway. if you wish to use such naming you need additional table where sz1 should have reference to var1.

regards!
Post 27 Mar 2006, 04:47
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bougainville



Joined: 27 Mar 2006
Posts: 8
bougainville
Thankyou shoorick. Yes, a table seems to be the way to go. I guess I was hoping that there might be an easier way because a table will get very big for many more variables. Also, there's the problem of adding to the table if a new variable comes by.
As I am essentially trying to parse an expression to perform arithmetic, perhaps there may be another completely different approach?
Post 28 Mar 2006, 00:14
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shoorick



Joined: 25 Feb 2005
Posts: 1605
Location: Ukraine
shoorick
i'm not ready to answer fast and full, but it does not look like a simple parser, much like simple HLL. there should be minimal set of functions: detecting vars, creating list of them, then, when they used in expression, replace them with their values, etc.
i would suggest you walk through the forth - it is excellent language to understand how expressions are solved and calculated.
Post 28 Mar 2006, 08:02
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