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Reference: dpANS 12.24

Section 7.6.5 Keyword Arguments in Generic Functions and Methods

Section 7.6.6 Method Selection and Combination

no-applicable-method, p.7-47

X3J13/92-3248 David Moon comment #48


Edit History: Version 1, 12/13/92, Kim Barrett

Status: Proposal NO-APPLICABLE-METHOD-FIRST passed (10+1)-0 on

letter ballot 93-302.

Problem Description:

There is no specification of the ordering between the check for

no-applicable-method and the check for unexpected keyword arguments.

Specifically, section 7.6.5 states that if a generic function is passed a

keyword argument that no applicable method accepts, an error should be

signaled, while section 7.6.6 states that if there are no applicable methods

then the generic function no-applicable-methods is called.


Check for no applicable method first. Change the end of the last paragraph

of section 7.6.6 from

If a \term{generic function} is called and no \term{methods} are

\term{applicable}, the \term{generic function} \funref{no-applicable-method}

is invoked.


If a \term{generic function} is called and no \term{methods} are

\term{applicable}, the \term{generic function} \funref{no-applicable-method}

is invoked, with the \term{results} from that call being used as the

\term{results} of the call to the original \term{generic function}. Calling

\funref{no-applicable-method} takes precedence over checking for acceptable

keyword arguments; \SeeSection{... section name for 7.6.5 ...}.

Editorial Impact:

Changing or adding a couple of lines of text.


It was clearly intended that the call to no-applicable-methods be for value,

rather than for effect. It just wasn't actually specified that way anywhere.

Adopting the suggested order would remove an ambiguity from the specification

and would make the no-applicable-method feature a little more useful.

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