5001 - drop the :(scenario) DSL

I've been saying for a while[1][2][3] that adding extra abstractions makes
things harder for newcomers, and adding new notations doubly so. And then
I notice this DSL in my own backyard. Makes me feel like a hypocrite.

[1] https://news.ycombinator.com/item?id=13565743#13570092
[2] https://lobste.rs/s/to8wpr/configuration_files_are_canary_warning
[3] https://lobste.rs/s/mdmcdi/little_languages_by_jon_bentley_1986#c_3miuf2

The implementation of the DSL was also highly hacky:

a) It was happening in the tangle/ tool, but was utterly unrelated to tangling
layers.

b) There were several persnickety constraints on the different kinds of
lines and the specific order they were expected in. I kept finding bugs
where the translator would silently do the wrong thing. Or the error messages
sucked, and readers may be stuck looking at the generated code to figure
out what happened. Fixing error messages would require a lot more code,
which is one of my arguments against DSLs in the first place: they may
be easy to implement, but they're hard to design to go with the grain of
the underlying platform. They require lots of iteration. Is that effort
worth prioritizing in this project?

On the other hand, the DSL did make at least some readers' life easier,
the ones who weren't immediately put off by having to learn a strange syntax.
There were fewer quotes to parse, fewer backslash escapes.

Anyway, since there are also people who dislike having to put up with strange
syntaxes, we'll call that consideration a wash and tear this DSL out.

---

This commit was sheer drudgery. Hopefully it won't need to be redone with
a new DSL because I grow sick of backslashes.

1 files changed, 75 insertions, 49 deletions

diff --git a/subx/034compute_segment_address.cc b/subx/034compute_segment_address.cc
index 79c6e45d..a1b7482d 100644
--- a/subx/034compute_segment_address.cc
+++ b/subx/034compute_segment_address.cc
@@ -2,17 +2,22 @@
 //: segment.
 //: This gives up a measure of control in placing code and data.
 
-:(scenario segment_name)
-== code
-05/add-to-EAX  0x0d0c0b0a/imm32
-# code starts at 0x08048000 + p_offset, which is 0x54 for a single-segment binary
-+load: 0x09000054 -> 05
-+load: 0x09000055 -> 0a
-+load: 0x09000056 -> 0b
-+load: 0x09000057 -> 0c
-+load: 0x09000058 -> 0d
-+run: add imm32 0x0d0c0b0a to reg EAX
-+run: storing 0x0d0c0b0a
+void test_segment_name() {
+  run(
+      "== code\n"
+      "05/add-to-EAX  0x0d0c0b0a/imm32\n"
+      // code starts at 0x08048000 + p_offset, which is 0x54 for a single-segment binary
+  );
+  CHECK_TRACE_CONTENTS(
+      "load: 0x09000054 -> 05\n"
+      "load: 0x09000055 -> 0a\n"
+      "load: 0x09000056 -> 0b\n"
+      "load: 0x09000057 -> 0c\n"
+      "load: 0x09000058 -> 0d\n"
+      "run: add imm32 0x0d0c0b0a to reg EAX\n"
+      "run: storing 0x0d0c0b0a\n"
+  );
+}
 
 //: Update the parser to handle non-numeric segment name.
 //:
@@ -61,44 +66,65 @@ if (Currently_parsing_named_segment) {
   return;
 }
 
-:(scenario repeated_segment_merges_data)
-== code
-05/add-to-EAX  0x0d0c0b0a/imm32
-== code
-2d/subtract-from-EAX  0xddccbbaa/imm32
-+parse: new segment 'code'
-+parse: appending to segment 'code'
-# first segment
-+load: 0x09000054 -> 05
-+load: 0x09000055 -> 0a
-+load: 0x09000056 -> 0b
-+load: 0x09000057 -> 0c
-+load: 0x09000058 -> 0d
-# second segment
-+load: 0x09000059 -> 2d
-+load: 0x0900005a -> aa
-+load: 0x0900005b -> bb
-+load: 0x0900005c -> cc
-+load: 0x0900005d -> dd
-
-:(scenario error_on_missing_segment_header)
-% Hide_errors = true;
-05/add-to-EAX 0/imm32
-+error: input does not start with a '==' section header
-
-:(scenario error_on_first_segment_not_code)
-% Hide_errors = true;
-== data
-05 00 00 00 00
-+error: first segment must be 'code' but is 'data'
-
-:(scenario error_on_second_segment_not_data)
-% Hide_errors = true;
-== code
-05/add-to-EAX 0/imm32
-== bss
-05 00 00 00 00
-+error: second segment must be 'data' but is 'bss'
+:(code)
+void test_repeated_segment_merges_data() {
+  run(
+      "== code\n"
+      "05/add-to-EAX  0x0d0c0b0a/imm32\n"
+      "== code\n"  // again
+      "2d/subtract-from-EAX  0xddccbbaa/imm32\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      "parse: new segment 'code'\n"
+      "parse: appending to segment 'code'\n"
+      // first segment
+      "load: 0x09000054 -> 05\n"
+      "load: 0x09000055 -> 0a\n"
+      "load: 0x09000056 -> 0b\n"
+      "load: 0x09000057 -> 0c\n"
+      "load: 0x09000058 -> 0d\n"
+      // second segment
+      "load: 0x09000059 -> 2d\n"
+      "load: 0x0900005a -> aa\n"
+      "load: 0x0900005b -> bb\n"
+      "load: 0x0900005c -> cc\n"
+      "load: 0x0900005d -> dd\n"
+  );
+}
+
+void test_error_on_missing_segment_header() {
+  Hide_errors = true;
+  run(
+      "05/add-to-EAX 0/imm32\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      "error: input does not start with a '==' section header\n"
+  );
+}
+
+void test_error_on_first_segment_not_code() {
+  Hide_errors = true;
+  run(
+      "== data\n"
+      "05 00 00 00 00\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      "error: first segment must be 'code' but is 'data'\n"
+  );
+}
+
+void test_error_on_second_segment_not_data() {
+  Hide_errors = true;
+  run(
+      "== code\n"
+      "05/add-to-EAX 0/imm32\n"
+      "== bss\n"
+      "05 00 00 00 00\n"
+  );
+  CHECK_TRACE_CONTENTS(
+      "error: second segment must be 'data' but is 'bss'\n"
+  );
+}
 
 //: compute segment address