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Comment by fuball63 | Hacker News Reader

Does that happen automatically in some cases? I think I'm on 8.6 and I'm pretty sure I forgot the expr and it worked OK. Could have been a string operation or something, I don't have the code to check on hand.

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The string command accepts a special syntax for indices, which includes addition (but not the full power of expr) [1]. Maybe you are referring to this? Also, list commands accept the same syntax for list indices.

Example:

    % string index abc 1
    b
    % string index abc 1+1
    c
    % string index abc 1+1+1
    bad index "1+1+1": must be integer?[+-]integer? or end?[+-]integer?
    % string index abc end-1
    b

[1] http://www.tcl.tk/man/tcl8.6/TclCmd/string.htm#M54

Well, you don't need 'expr' in contexts were an expression is expected, e.g. 'if' 'while', 'for' (2nd arg).

I think that this is what I was experiencing.

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