Topic: temporary data objects

Summary

Languages with expressions need temporaries to store intermediate results. Temporaries are system defined variables which are not directly accessible to the user. Their values have situation-dependent meanings, and may require a larger value precision. A stack is usually used for storing temporaries because intermediate values are embedded in expression evaluation. Temporaries are usually primitive values because data structures consume large amounts of memory. But in Jackson's design method temporary files are needed to resolve structure clashes where program and data no longer match. Temporary files and data structures can be avoided by coroutines (Jackson's "program inversion") or structure modification. Some languages provide the user with temporaries which are pre-named variables. Comit (QuoteRef: sammJE_1969

Subtopic: type of temporary

Note: type represents what doesn't change; e.g., a boolean is 1 bit; allows temporaries of some type [»cbb_1990, OK]

Subtopic: temporary files

Quote: JacksonDesignMethod uses unstructured temporary files to avoid structure clashes [»jackMA_1975]

Quote: Comit uses shelves for temporaries which act as queues [»sammJE_1969, OK]

Quote: create temporary files be deleting a file while it is open; the unnamed file vanishes when closed [»thomK7_1978]

Subtopic: temporary structures

Quote: temporary integers are inexpensive but temporary structures are expensive; structures need update instead of value [»hoarCA_1973, OK]

Subtopic: intermediate result

Quote: in proofs of concurrent programs need to introduce value variables for intermediate results [»lampL_1980]

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Topic: system-defined variables
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