One problem language designers face is handling embedded comments. The basic problem is that if you comment out a large block, your intent might be thwarted by comments within the block. For example in C, the /* symbol marks the beginning of a block and */ the end. To comment out a block of code it's not sufficient to place these markers at the beginning or end of the block, because if a */ occurs inside the block, it will close the comment. So, most languages forbid the use of embedded comments. (As a result, various work-arounds are used. In C, for example, the #if 0 / #endif combo is used.)
Lua, which is a nifty dynamic language, is the first language I've seen to come up with a solution to this problem. Here goes:
In Lua, block comments start with: --[[ and end with --]] If you want to comment out a chunk that might contain block comments, you can add one or more = signs between the brackets: Open with --[=[ and close with ]=]. You can use any number of = signs between the brackets and Lua will comment out everything until it finds a pair of closing brackets with a matching number of equal signs. So, --[==[ and ]==] or --[===[ and ]===] are valid comment block markers. You can use as many equal signs as you want, as long as beginning and ending counts match. So, you can always block out your code regardless of how many embedded comments it might contain.
I think that's pretty clever. Anyone know of another language with a similar mechanism?
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