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Lisp originally had very few control structures, but many more were added during the language's evolution. (Lisp's original conditional operator, cond, is the precursor to later if-then-else structures.) Programmers in the Scheme dialect often express loops using tail recursion. Scheme's commonality in academic computer science has led some ...
tagbody is a primitive Common Lisp special operator which provides the ability to name tags and use the go form to jump to those tags. The backquote ` provides a notation that provides code templates, where the value of forms preceded with a comma are filled in. Forms preceded with comma and at-sign are spliced in. The tagbody form tests the ...
For example, the Lisp expression (cons 1 2) constructs a cell holding 1 in its left half (the so-called car field) and 2 in its right half (the cdr field). In Lisp notation, the value (cons 1 2) looks like: (1 . 2) Note the dot between 1 and 2; this indicates that the S-expression is a "dotted pair" (a so-called "cons pair"), rather than a "list."
Lisp was originally implemented on the IBM 704 computer, in the late 1950s.. The popular explanation that CAR and CDR stand for "Contents of the Address Register" and "Contents of the Decrement Register" [1] does not quite match the IBM 704 architecture; the IBM 704 does not have a programmer-accessible address register and the three address modification registers are called "index registers ...
Lisp programs are valid S-expressions, but not all S-expressions are valid Lisp programs. (1.0 + 3.1) is a valid S-expression, but not a valid Lisp program, since Lisp uses prefix notation and a floating point number (here 1.0) is not valid as an operation (the first element of the expression).
In most languages, functions may be seen as a special form of prefix operator with fixed precedence level and associativity, often with compulsory parentheses e.g. Func(a) (or (Func a) in Lisp). Most languages support programmer-defined functions, but cannot really claim to support programmer-defined operators, unless they have more than prefix ...
The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard ...
In logic, a set of symbols is commonly used to express logical representation. The following table lists many common symbols, together with their name, how they should be read out loud, and the related field of mathematics.