eager evaluation

Any evaluation strategy where evaluation of some or all

function arguments is started before their value is required.

A typical example is call-by-value, where all arguments are

passed evaluated. The opposite of eager evaluation is

call-by-need where evaluation of an argument is only started

when it is required.

The term "speculative evaluation" is very close in meaning

to eager evaluation but is applied mostly to parallel

architectures whereas eager evaluation is used of both

sequential and parallel evaluators.

Eager evaluation does not specify exactly when argument

evaluation takes place - it might be done fully speculatively

(all redexes in the program reduced in parallel) or may be

done by the caller just before the function is entered.

The term "eager evaluation" was invented by Carl Hewitt and

Henry Baker [email protected] and used in their paper ["The

Incremental Garbage Collection of Processes", Sigplan Notices,

Aug 1977.

]. It was

named after their "eager beaver" evaluator.

See also conservative evaluation, lenient evaluation,

strict evaluation.

(1994-12-22)