Interpreter coverage

What packages/cobol-backend emits, against what packages/cobol-runtime can execute. A verb in the first and not the second is a differential blind spot: the compiled side runs, the interpreted side refuses, and the comparison that gives this project's green its meaning does not happen.

Measured over the 158 programs the compiler produces from the examples and the benchmark tasks.

The denominator is locally executable emitted verbs, not all of them. A verb whose only home is a zUnit test case or a Report Writer section has nowhere local to run whatever the interpreter implements, and counting it as a gap made the real one look half its size: of eight blind spots reported before SORT and MERGE were built, four were those two and their RELEASE and RETURN, and four were exempt. Each exemption carries its reason below and is held to a named program by tests/interpreter-coverage.test.ts.


verbs emitted	31
of those, locally executable	27
of those, interpreted	27
differential blind spots	0
exempt, with a recorded reason	4

Every locally executable verb the backend emits can be executed by both engines.

Every emitted verb

Verb	Emitted	Locally executable	Interpreted
`MOVE`	2305	yes	yes
`IF`	699	yes	yes
`DISPLAY`	657	yes	yes
`PERFORM`	201	yes	yes
`COMPUTE`	197	yes	yes
`CONTINUE`	165	yes	yes
`EXIT`	146	yes	yes
`CALL`	103	yes	yes
`ADD`	83	yes	yes
`CLOSE`	76	yes	yes
`OPEN`	75	yes	yes
`GOBACK`	55	yes	yes
`WRITE`	55	yes	yes
`READ`	46	yes	yes
`SET`	23	yes	yes
`EVALUATE`	18	yes	yes
`STRING`	14	yes	yes
`SUBTRACT`	10	yes	yes
`ENTRY`	6	no	n/a
`INITIALIZE`	6	yes	yes
`INSPECT`	6	yes	yes
`DIVIDE`	4	yes	yes
`UNSTRING`	3	yes	yes
`RELEASE`	2	yes	yes
`SORT`	2	yes	yes
`GENERATE`	1	no	n/a
`INITIATE`	1	no	n/a
`MERGE`	1	yes	yes
`RETURN`	1	yes	yes
`START`	1	yes	yes
`TERMINATE`	1	no	n/a

Emitted, and outside local execution

Verb	In	Why no local run reaches it
`ENTRY`	(generated)/TZUNITTE.cbl	an alternate entry point in a generated zUnit test case. It is called by IBM's zUnit runner, which is not on this machine, and never by a job step.
`GENERATE`	examples/report-with-controls	Report Writer, as INITIATE.
`INITIATE`	examples/report-with-controls	Report Writer, expanded by IBM's Report Writer precompiler. `packages/cobol-runtime` refuses a REPORT SECTION by name rather than implementing page fitting, control breaks and sum counters a second time.
`TERMINATE`	examples/report-with-controls	Report Writer, as INITIATE.

Not executable locally, as whole statements

EXEC CICS, EXEC SQL — these need Db2, a CICS region or IMS. The reference modules under runtime/ stand in well enough to run a program, which falls well short of executing SQL. They are not counted as gaps because no interpreter change would close them.

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