Group:
naming
Topic:
abstraction in programming language
Topic:
alias names
Topic:
binding of names to objects
Topic:
binding names to variables or expressions
Topic:
constants
Topic:
definition languages
Topic:
environment variables
Topic:
function definition
Topic:
implementation of Thesa data objects
Topic:
initialized constants
Topic:
macros
Topic:
non-primitive values
Topic:
parameter passing by name
Topic:
replacement as defining a variable
Topic:
symbolic representation
Topic:
value as an object
Topic:
variables for array bounds
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Summary
Literals are names for constants, expressions, or values. They are a form of paraphrase extension and abstraction. Constants or expressions have many possible meanings. For instance 425 may be the address of an edit routine, the number of apples in a crate, the melting point of a metal, the maximum number of man-hours allocated to a project, or the price of a radio. By naming constants and expressions the programmer specifies a particular meaning for what would have been a mystery number. Since literals stand for a value, they are equivalent to functions without arguments. The expression or constant associated with a literal cannot be changed. Dynamic constants are literals defined during execution. Their use within a procedure or refinement requires unique system generated names. If function definition is a legitimate value then the function's name is a literal standing for its definition. (cbb 5/80)
Subtopic: named constant 
| Quote: a named constant is defined exactly once; any expression involving name constants has a fixed value as long as they are defined [»redeDH7_1979]
| | Quote: a 'const' reference can be the address of an initialized temporary; allows flexible initialization; useful for function arguments [»stroB_1991]
| | Quote: a C++ reference to a type is a synonym for the variable it is initialized to; used for overloaded operators, functions, and both sides of assignments [»stroB_1991]
| | Quote: global named constants are "wired in"; prevents multiple calls to a refinement [»redeDH7_1979]
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Subtopic: system configuration
| Quote: classify parameters by likelihood of change and cost of variability; use run-time variables if low cost, system configuration variables if unlikely to change [»britKH3_1981]
| | Quote: use reconfiguration interfaces for device-dependent characteristics that vary at run-time; e.g., drift rate [»britKH3_1981]
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Subtopic: named constants vs. numbers
| Quote: banned all mystery numbers above two [»clarBL9_1973]
| | Quote: with run-time translation of keys and offsets, would never use numbers except when desired [»lost entries, OK]
| | Quote: essential information in a specification must not rely on arbitrary details; e.g., use mnemonic names instead of numbers or sequences [»heniKL1_1980]
| | Quote: a manuscript should refer to files through indirect symbolic names; prevents dependence on a particular installation [»reidBK_1980]
| | Quote: produce special purpose instructions by using mnemonic abbreviations for computations of some given type
| | Quote: use abbreviations to indicate dialing information, allows the same phone number to be stored at every site; e.g., nyc or boston [»nowiDA8_1978]
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Subtopic: constant as function
| Quote: a constant in Russell is any value-producing function of no arguments; must produce constant results [»demeA3_1979]
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Subtopic: constant as function definition
| Quote: parameters carry values into refinements; global named constants carry values out [»redeDH7_1979]
| | Quote: in Forth, the constant EDIT is the address of the block that contains the editor; so EDIT LOAD loads the editor [»ewinMS9_1974]
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Subtopic: examples
| Quote: in C, defined constants are usually upper-case names to distinguish from variables [»ritcDM7_1978c]
| Quote: by defining constants via a macro processor, C allows any string of characters to be substituted
[»ritcDM7_1978c]
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Related Topics
Group: naming (32 topics, 789 quotes)
Topic: abstraction in programming language (47 items)
Topic: alias names (39 items)
Topic: binding of names to objects (19 items)
Topic: binding names to variables or expressions (10 items)
Topic: constants (21 items)
Topic: definition languages (3 items)
Topic: environment variables (5 items)
Topic: function definition (25 items)
Topic: implementation of Thesa data objects (27 items)
Topic: initialized constants (12 items)
Topic: macros (22 items)
Topic: non-primitive values (11 items)
Topic: parameter passing by name (11 items)
Topic: replacement as defining a variable (8 items)
Topic: symbolic representation (26 items)
Topic: value as an object (29 items)
Topic: variables for array bounds
(7 items)
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