Forth 2012: :

( C: "<spaces>name" -- colon-sys )

Skip leading space delimiters. Parse name delimited by a space. Create a definition for name, called a "colon definition". Enter compilation state and start the current definition, producing colon-sys. Append the initiation semantics given below to the current definition.

The execution semantics of name will be determined by the words compiled into the body of the definition. The current definition shall not be findable in the dictionary until it is ended (or until the execution of DOES> in some systems).

Initiation:

( i * x -- i * x ) ( R: -- nest-sys )

Save implementation-dependent information nest-sys about the calling definition. The stack effects i * x represent arguments to name.

name Execution:

( i * x -- j * x )

Execute the definition name. The stack effects i * x and j * x represent arguments to and results from name, respectively.

See:

3.4.3.2 Interpretation semantics, 3.4.1 Parsing, 3.4.5 Compilation, 6.1.1250 DOES>, 6.1.2500 [, 6.1.2540 ], 15.6.2.0470 ;CODE, A.6.1.0450 :.

Rationale:

Typical use: : name ... ;

In Forth 83, this word was specified to alter the search order. This specification is explicitly removed in this standard. We believe that in most cases this has no effect; however, systems that allow many search orders found the Forth-83 behavior of colon very undesirable.

Note that colon does not itself invoke the compiler. Colon sets compilation state so that later words in the parse area are compiled.

Testing:

T{ : NOP : POSTPONE ; ; -> }T
T{ NOP NOP1 NOP NOP2 -> }T
T{ NOP1 -> }T
T{ NOP2 -> }T

The following tests the dictionary search order:

T{ : GDX 123 ; : GDX GDX 234 ; -> }T
T{ GDX -> 123 234 }T