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For example, 0x10ULL evaluates to the value 16 as an unsigned long long integer in C++: the 0x prefix indicates hexadecimal, while the suffix ULL indicates unsigned long long. Similarly, prefixes are often used to indicate a raw string , such as r"C:\Windows" in Python, which represents the string with value C:\Windows ; as an escaped string ...
In the above example, form1 contains the symbol +. Evaluation of this symbol must yield the function for addition to make the example work as intended. Thus some dialects of Lisp allow an additional parameter for eval to specify the context of evaluation (similar to the optional arguments to Python's eval function - see below).
The length of a string can also be stored explicitly, for example by prefixing the string with the length as a byte value. This convention is used in many Pascal dialects; as a consequence, some people call such a string a Pascal string or P-string .
In Python, functions are first-class objects, just like strings, numbers, lists etc. This feature eliminates the need to write a function object in many cases. Any object with a __call__() method can be called using function-call syntax. An example is this accumulator class (based on Paul Graham's study on programming language syntax and ...
As another example, the scope resolution operator :: and the element access operator . (as in Foo::Bar or a.b) operate not on values, but on names, essentially call-by-name semantics, and their value is a name. Use of l-values as operator operands is particularly notable in unary increment and decrement operators. In C, for instance, the ...
A string literal or anonymous string is a literal for a string value in the source code of a computer program. Modern programming languages commonly use a quoted sequence of characters, formally "bracketed delimiters", as in x = "foo" , where , "foo" is a string literal with value foo .
If a symbol is unknown, the Lisp reader creates a new symbol. In Common Lisp, symbols have the following attributes: a name, a value, a function, a list of properties and a package. [6] In Common Lisp it is also possible that a symbol is not interned in a package. Such symbols can be printed, but when read back, a new symbol needs to be created.
Python supports a wide variety of string operations. Strings in Python are immutable, so a string operation such as a substitution of characters, that in other programming languages might alter the string in place, returns a new string in Python. Performance considerations sometimes push for using special techniques in programs that modify ...