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Lines that are only run sometimes

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if, else, end, and same.

IF TAKES A COMMAND, which is one rule rather than two and is why comparing
values needs no syntax of its own: "same" is an ordinary command that fails when
its two words differ, so "if same $a $b" falls out of the rule instead of being
an exception to it. Anything else that can fail is a question too - "if load
Snake.sbx" is a perfectly good one.

The shell already had the other half. LineFailed exists because a script stops at
the first line that did not work, so every command was already saying whether it
had, for a different reason entirely.

A BLOCK HAS TWO KINDS OF NOT-RUNNING. One where an else would turn it on, and
one where it would not - which is what an if pushes when something above it is
already being skipped. That is what makes nesting need no looking down the
stack: the top of it says everything.

A branch nobody is taking is not even looked at. The skipping happens BEFORE the
names are filled in, so a variable mentioned in a branch that is not running is
not an error - a line nobody runs must not be able to fail.

AND LINES MAY BE INDENTED, which they could not be before there was anything to
indent inside. Nobody writes an if inside an if without indenting what is in
them, and a leading space used to make the first word empty and match nothing.
Found by writing the test script the way anybody would write one.

CALL commandFailed became BRI commandFailed in nine places. It never returns - it
marks the line and branches to the prompt - so calling it was a lie that cost a
Stack frame each time, and fourteen other sites already branched. THE LINT RULE
FOUND THIS, three days after I wrote the rule and on my own code: two false
positives that were really the linter being right about a CALL that is not one.
It does not fix the leak on its own, since a failure inside any called routine
still abandons that frame, but it removes the cause of the commonest case and
makes the code true.

The mechanical edit then left a BRI prompt stranded behind one of them, and the
linter caught that too.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
This commit is contained in:
Anachronaut
2026-09-01 20:33:33 -04:00
co-authored by Claude Opus 5
parent 4b109f704c
commit 16f8232a35
15 changed files with 523 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Tests/expected/cosmosBlocks.out
+54
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@@ -0,0 +1,54 @@
CosmOS
> set a hello
> if same $a hello
> echo taken
taken
> else
> echo not taken
> end
> if load nosuch.sbx
no such file
> echo loaded
> else
> echo did not
did not
> end
> else
else with no if above it
> end
end with no if above it
> if
if wants a command to decide by
> do blocks.script
> set colour red
> if same $colour red
> echo it is red
it is red
> if same $colour blue
> echo and blue
> else
> echo but not blue
but not blue
> end
> else
> echo $neverSetAnywhere
> end
> if same $colour blue
> echo wrong
> else
> echo right
right
> end
> if same $colour blue
> if same $colour red
> echo deep wrong
> else
> echo deep also wrong
> end
> end
> echo done
done
> exit
halted
Execution halted.
[exit 0]
Tests/expected/cosmosCrossDisk.out
+2 -1
View File
@@ -24,6 +24,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -36,7 +37,7 @@ outer.script 376
inner.script 44
loop.script 35
crossed.txt 560
23 files, 1 directory
24 files, 1 directory
> exit
halted
Execution halted.
Tests/expected/cosmosDrives.out
+2 -1
View File
@@ -14,6 +14,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -25,7 +26,7 @@ nonl.script 38
outer.script 376
inner.script 44
loop.script 35
22 files, 1 directory
23 files, 1 directory
> drive 1
> dir
other.txt 28
Tests/expected/cosmosFault.out
+2 -1
View File
@@ -31,6 +31,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -42,7 +43,7 @@ nonl.script 38
outer.script 376
inner.script 44
loop.script 35
22 files, 1 directory
23 files, 1 directory
> exit
halted
Execution halted.
Tests/expected/cosmosGrid.out
+2 -1
View File
@@ -21,6 +21,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -32,7 +33,7 @@ nonl.script 38
outer.script 376
inner.script 44
loop.script 35
22 files, 1 directory
23 files, 1 directory
> exit
halted
Execution halted.
Tests/expected/cosmosMonitor.out
+2 -1
View File
@@ -107,6 +107,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -118,7 +119,7 @@ nonl.script 38
outer.script 376
inner.script 44
loop.script 35
22 files, 1 directory
23 files, 1 directory
> exit
halted
Execution halted.
Tests/expected/cosmosMonitorRun.out
+2 -1
View File
@@ -26,6 +26,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -37,7 +38,7 @@ nonl.script 38
outer.script 376
inner.script 44
loop.script 35
22 files, 1 directory
23 files, 1 directory
> exit
halted
Execution halted.
Tests/expected/cosmosRun.out
+2 -1
View File
@@ -14,6 +14,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -25,7 +26,7 @@ nonl.script 38
outer.script 376
inner.script 44
loop.script 35
22 files, 1 directory
23 files, 1 directory
> load
load what?
> load nosuch.sbx
Tests/expected/cosmosSlowDisk.out
+2 -1
View File
@@ -12,6 +12,7 @@ Press.sbx 872
Mode.sbx 48
Crash.sbx 632
vars.script 50
blocks.script 343
tune.sbx 306
notes.txt 21
Apps <dir>
@@ -23,7 +24,7 @@ nonl.script 38
outer.script 376
inner.script 44
loop.script 35
22 files, 1 directory
23 files, 1 directory
> load Say.sbx
loaded, starting at 5000
> run the disk took its time
Tests/input/cosmosBlocks.in
+16
View File
@@ -0,0 +1,16 @@
set a hello
if same $a hello
echo taken
else
echo not taken
end
if load nosuch.sbx
echo loaded
else
echo did not
end
else
end
if
do blocks.script
exit
Tests/makedisks.sh
+5
View File
@@ -132,7 +132,12 @@ for i in 1 2 3 4 5 6 7 8; do "$TOOL" put "$DISKS/sbfs.img" "filler$i.txt" >/dev/
# A script that names something nothing was ever set to. Stop on failure is what says the
# expansion really did fail rather than merely complaining: the line after it must not run.
printf '#! script\necho before\necho $nosuchname\necho after\n' > vars.script
# A script with blocks in it, because that is where they are actually for. It nests, it
# takes the second branch of an outer if, and the branch nobody takes mentions a name that
# was never set - which must not be an error, because nothing there is being run.
printf '#! script\nset colour red\nif same $colour red\n echo it is red\n if same $colour blue\n echo and blue\n else\n echo but not blue\n end\nelse\n echo $neverSetAnywhere\nend\nif same $colour blue\n echo wrong\nelse\n echo right\nend\nif same $colour blue\n if same $colour red\n echo deep wrong\n else\n echo deep also wrong\n end\nend\necho done\n' > blocks.script
"$TOOL" put "$DISKS/cosmos.img" vars.script >/dev/null
"$TOOL" put "$DISKS/cosmos.img" blocks.script >/dev/null
# tune.sbx, which used to be a boot image and is now a program like any other. It brings a
# vector of its own - the screen's, so that it has a beat to play to - which makes it the
# second thing here that the version two format exists for.
Tests/manifest
+13
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@@ -425,6 +425,19 @@ cosmosVars | CosmOS/Source/cosmos.asm | run | cosmosVar
# Break is what makes it visible, because it prints the registers. The two dumps have to
# agree, and the failures between them are what would move it.
cosmosStack | CosmOS/Source/cosmos.asm | run | cosmosStack.in | - | disks/cosmos.img
# Lines that are only run sometimes. "if" takes a COMMAND and what follows runs only if that
# command worked - the Bourne shell's answer, and the reason "test" exists there: one rule in
# if, and comparing two things is just another command that can fail. Here that command is
# "same", and the shell already had the other half in LineFailed.
#
# AN if INSIDE A BRANCH NOBODY IS TAKING IS NOT A QUESTION. Its else must not run either, so
# it is pushed as a block that neither branch of can be taken - which is why a block has two
# kinds of not-running rather than one, and why nesting needs no looking down the stack.
#
# THE BRANCH NOBODY TAKES IS NOT EVEN LOOKED AT. The script names a variable that was never
# set, inside the branch that is not taken, and that must not be an error - so the skipping
# happens before the names are filled in, and a line nobody is running cannot fail.
cosmosBlocks | CosmOS/Source/cosmos.asm | run | cosmosBlocks.in | - | disks/cosmos.img
# The same editing offered to a PROGRAM, through osReadLine. Edit reads its lines that way,
# so a word typed with two letters the wrong way round is put right without starting the line
# again - which is the whole of what A4 buys.