6.1.1250
DOES>
does
CORE
Interpretation:
Interpretation semantics for this word are undefined.

Compilation:
( C: colon-sys1 -- colon-sys2 )

Append the run-time semantics below to the current definition. Whether or not the current definition is rendered findable in the dictionary by the compilation of DOES> is implementation defined. Consume colon-sys1 and produce colon-sys2. Append the initiation semantics given below to the current definition.

Run-time:
( -- ) ( R: nest-sys1 -- )

Replace the execution semantics of the most recent definition, referred to as name, with the name execution semantics given below. Return control to the calling definition specified by nest-sys1. An ambiguous condition exists if name was not defined with CREATE or a user-defined word that calls CREATE.

Initiation:
( i * x -- i * x a-addr ) ( R: -- nest-sys2 )

Save implementation-dependent information nest-sys2 about the calling definition. Place name's data field address on the stack. The stack effects i * x represent arguments to name.

name Execution:
( i * x -- j * x )

Execute the portion of the definition that begins with the initiation semantics appended by the DOES> which modified name. The stack effects i * x and j * x represent arguments to and results from name, respectively.

See:
6.1.1000 CREATE, A.6.1.1250 DOES>.

Rationale:
Typical use: : X ... DOES> ... ;

Following DOES>, a Standard Program may not make any assumptions regarding the ability to find either the name of the definition containing the DOES> or any previous definition whose name may be concealed by it. DOES> effectively ends one definition and begins another as far as local variables and control-flow structures are concerned. The compilation behavior makes it clear that the user is not entitled to place DOES> inside any control-flow structures.

Testing:
T{ : DOES1 DOES> @ 1 + ; -> }T
T{ : DOES2 DOES> @ 2 + ; -> }T
T{ CREATE CR1 -> }T
T{ CR1   -> HERE }T
T{ 1 ,   ->   }T
T{ CR1 @ -> 1 }T
T{ DOES1 ->   }T
T{ CR1   -> 2 }T
T{ DOES2 ->   }T
T{ CR1   -> 3 }T

T{ : WEIRD: CREATE DOES> 1 + DOES> 2 + ; -> }T
T{ WEIRD: W1 -> }T
T{ ' W1 >BODY -> HERE }T
T{ W1 -> HERE 1 + }T
T{ W1 -> HERE 2 + }T