Call by Name

This (in-)famous parameter passing mode was introduced as the default mode in Algol-60. It was elegant, surprising, and, at the time of introduction, horribly inefficient.

For this reason, it was not adapted in later programming languages. Instead, procedure types or explicit anonymous procedures were used.

Call by name treats the actual parameter as an implicit anonymous procedure with no parameters but with a lexical closure. It is passed in form of a so-called thunk (a reference to the anonymous procedure) and evaluated only if necessary. However, it is not the normal form of lazy evaluation as the parameter is newly evaluated on each access.

If just a variable is passed, call-by-name is equivalent to call-by-reference. In case of actual parameters that are constant expressions, call-by-name is equivalent to call-by-value.

	This (in-)famous parameter passing mode was introduced as the default mode in Algol-60. It was elegant, surprising, and, at the time of introduction, horribly inefficient.
	For this reason, it was not adapted in later programming languages. Instead, procedure types or explicit anonymous procedures were used.
	Call by name treats the actual parameter as an implicit anonymous procedure with no parameters but with a lexical closure. It is passed in form of a so-called thunk (a reference to the anonymous procedure) and evaluated only if necessary. However, it is not the normal form of lazy evaluation as the parameter is newly evaluated on each access.
	If just a variable is passed, call-by-name is equivalent to call-by-reference. In case of actual parameters that are constant expressions, call-by-name is equivalent to call-by-value.