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Literals in Programming Languages
- tantalor 14y ago> Booleans are ordinal values and usually false is less than true. I was surprised to find this is true, http://plato.stanford.edu/entries/truth-values/#3 http://plato.stanford.edu/entries/truth-values/#3
- jonsen 14y agoSo in fact you believed it was false before true then ;-)
- ibotty 14y agowell i believed that they are not ordered. (which they are not in some languages)
- tantalor 14y agoThat's what I thought, but it appears truth values are typically defined with a partial ordering a <= b iff a && b == a, which gives false <= false < true <= true. You could choose to ignore that partial ordering at your own peril.
- cpeterso 14y agoIn Visual Basic, False is 0 and True is -1.
- ubernostrum 14y agoIn Python, bool is a subclass of int. The constants True and False have the values 1 and 0 respectively, and it's legal to do arithmetic with them :)
- jmmcd 14y agoThis article is only about primitive literals, not compound ones. I think the list and dict literals in Python are the #1 reason I like it better than C. I think the regexp literals in Perl were one of the main reasons people liked Perl better than C.
- mahmud 14y agoThat line blurs when you have homoiconic syntax, specially one with a programmable reader. Common Lisp uses the # for dispatch macro character, you can define your own literals, in whatever environment you want. http://www.franz.com/support/documentation/6.2/ansicl/subsecti/sharpsig.htm http://www.franz.com/support/documentation/6.2/ansicl/subsec...
- pilgrim689 14y ago> I like [Python] better than C Isn't it strange to compare Python/Perl to C and say that one is better than the other? It's apples to oranges. You wouldn't use Python or Perl to build an OS, and you wouldn't use C to prototype a web app.
- jmmcd 14y agoSure, but I said "like", not "better". When I learned Python, I had that feeling described as weightlessness by xkcd [http://xkcd.com/353/ http://xkcd.com/353/], because I didn't have to write several lines and a loop to make a list. It made me happy. Fair comparisons don't really come into it.
- anders0 14y agoTo nitpick, -14 isn't a literal in all languages. :) (In Haskell, it's just sugar for negate 14, while in Standard ML it's spelt ~14. And I assume there are other exceptions too.)
- pdw 14y agoEven in C it's not a literal. The consequence is that in a 32-bit implementation, you can't write INT_MIN as -2147483648 (-2^31), because 2147483648 would overflow a signed int. Instead a workaround such as -2147483647-1 must be used.
- anders0 14y agoHuh. I always assumed it was in C. Shows what I know… :p
- shaurz 14y agoMaking the minus part of the literal can lead to parsing ambiguity. For example, "x-3" would parse as 2 tokens "x" and "-3" (instead of 3 tokens "x", "-" and "3") which would be a syntax error in C. The only workaround I can think of is making any expression followed by a negative number parse as a subtraction.
- reycharles 14y ago> Making the minus part of the literal can lead to parsing ambiguity. Not really. It's done in java. Usually, minus ("-") is parsed as a token and then unary minus on integer literals are transformed to a negative integer literal. So, -2147483648 is read as MINUS INT_LITERAL and thus transformed into "-2147483648" as an INT_LITERAL, but -(2147483648) should be read as MINUS L_PAREN INT_LITERAL R_PAREN and should thus not be transformed.
- swah 14y agoFactor has them for many data-structures: http://docs.factorcode.org/content/article-syntax-literals.html http://docs.factorcode.org/content/article-syntax-literals.h..., but they are simple to add in a concatenative language (they might as well have been added by a user library).