Topic: constants

topics > computer science > data > Group: data value

compile-time execution
data type by lexical constraints
data structure literals
default value
enumerated data types
initialization of data
initialized constants
integer values and operations
kinds of numbers
named constants and expressions
notation for constants
object-defined names
primitive functions
string literals
undefined, null, and other signal values
value as an abstraction


A constant is a name that designates one or more values, where a value is an immutable bit string plus data type. (Can/should '0' be an object?) Generally a lexical pattern identifies the constant's data types and a procedure for that data type converts the name into a bit string. The name can include a unit specifier that qualifies the data type or bit string. (cbb 1/90)

A constant is a token string which when given to a string-to-value procedure produces a typed value. A numerical constant consists of digits, type identifying characters and component deliminators. Enumerated types define new constants. The value associated with a constant is usually context independent, but a target type may be defined. For instance 'R:=3' may produce a real number with value 3. An expression of constants may also be considered a constant if there exists a string interpreter function. Many different strings will produce the same typed value. These strings may be defined via a template or conversion function. One of the strings is the output format defined by a value-to-string function. Constants make an abstract program concrete because of their fixed meaning. One of a language's boundaries is that constants can't be modified or replaced. (cbb 5/80)

Subtopic: constants as values, permanent name up

Quote: symbols that are valid handles to objects in most scopes are typically recognized syntactically, e.g., numbers, symbols, and strings [»kentW6_1991]
Quote: constants are terms that are their own value [»memorex]
Quote: a constant is a permanent name for a value; a variable is a temporary name [»hehnEC7_1975]
Quote: a literal is a constant variable whose value is suggested by its print name [»wulfWA4_1974]
Quote: the value of a literal is the literal itself; e.g., true, false, and .capOmega. as undefined [»wirtN1_1966]
Quote: a denotation is a self-defining name for a value; e.g., '2' [»maclBJ12_1983]

Subtopic: constants as attributes up

QuoteRef: memorex ;;2-22 can get length of a symbol's value in storage words

Subtopic: constant data structures up

Quote: in CmLisp, use .alpha. to convert a value into a constant xector; i.e., the value is loaded into every processor [»hillWD_1985]
Quote: in CmLisp, use .bullet. to selectively cancel the constant meta-operation .alpha. [»hillWD_1985]
Quote: think of CmLisp's .alpha. as a way to get a zillion of something; .bullet. marks subexpressions that already have a zillion [»hillWD_1985]

Subtopic: data exchange up

Quote: Kleisli's data exchange format is CPL values; self-describing, e.g., {| indicates a bag; no fixed schema or type declaration [»wongL9_2000]

Subtopic: type compatible up

Quote: a constant is type compatible if it can be a value of that type; it can be compatible with many types [»clayR4_1978]

Subtopic: expression of constants up

Quote: any construct that requires a constant should also allow an expression of constants [»knobB4_1976]

Subtopic: enumeration up

Quote: use enumerated data type to define a new set of constants [»demeA3_1979]

Subtopic: data flow up

QuoteRef: kosiPR9_1973 ;;94 in a data flow language, CONSTANT provides a constant value that always has PRESENCE and can't receive input

Subtopic: compiling constants up

Quote: C# constants are computed at compile time and accessed via their class [»wiltS10_2000]
QuoteRef: cbb_1973 ;;Algol handles literal constants by calling the appropriate runtime conversion routine
Quote: Proteus included the format of literals as part of a type definition [»solnN_1971, OK]
Quote: the syntax of a literal defines a calculation that converts a print name into an internal value [»wulfWA4_1974]
Quote: define the set CONST by functions const? and evcon; evcon maps each constant into the value it denotes [»reynJC8_1972]

Subtopic: code constants up

Quote: executable code should not be modified; was a big clarity problem with machine code

Related Topics up

Topic: compile-time execution (17 items)
Topic: data type by lexical constraints (15 items)
Topic: data structure literals (9 items)
Topic: default value (8 items)
Topic: enumerated data types (17 items)
Topic: initialization of data (45 items)
Topic: initialized constants (12 items)
Topic: integer values and operations (13 items)
Topic: kinds of numbers (24 items)
Topic: named constants and expressions (21 items)
Topic: notation for constants (14 items)
Topic: object-defined names (15 items)
Topic: primitive functions (34 items)
Topic: string literals (3 items)
Topic: strings (13 items)
Topic: undefined, null, and other signal values (34 items)
Topic: value as an abstraction
(25 items)

Updated barberCB 4/04
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