43 files changed, 89 insertions, 98 deletions

diff --git a/011run.cc b/011run.cc
index 194676d8..585f9930 100644
--- a/011run.cc
+++ b/011run.cc
@@ -27,7 +27,7 @@ put_new(Help, "syntax",
   "after a '/', but they can never contain whitespace. Metadata has no effect\n"
   "at runtime, but can be handy when rewriting macros.\n"
   "\n"
-  "Check out the examples in the examples/ directory.\n"
+  "Check out the example programs in the apps/ directory, particularly apps/ex*.\n"
 );
 :(before "End Help Contents")
 cerr << "  syntax\n";
diff --git a/Readme.md b/Readme.md
index 1d0329de..04bd4b5a 100644
--- a/Readme.md
+++ b/Readme.md
@@ -48,7 +48,7 @@ In priority order:
 
 You get a thin syntax called SubX for programming in (a subset of) x86 machine
 code. (A memory-safe compiled language is [being designed](http://akkartik.name/post/mu-2019-2).)
-Here's a program (`examples/ex1.subx`) that returns 42:
+Here's a program (`apps/ex1.subx`) that returns 42:
 
   ```sh
   bb/copy-to-ebx  0x2a/imm32  # 42 in hex
@@ -59,8 +59,8 @@ Here's a program (`examples/ex1.subx`) that returns 42:
 You can generate tiny zero-dependency ELF binaries with it that run on Linux.
 
   ```sh
-  $ ./subx translate init.linux examples/ex1.subx -o examples/ex1  # on Linux or BSD or Mac
-  $ ./examples/ex1  # only on Linux
+  $ ./subx translate init.linux apps/ex1.subx -o apps/ex1  # on Linux or BSD or Mac
+  $ ./apps/ex1  # only on Linux
   $ echo $?
   42
  ```
@@ -72,7 +72,7 @@ You can run the generated binaries on an interpreter/VM for better error
 messages.
 
   ```sh
-  $ ./subx run examples/ex1  # on Linux or BSD or Mac
+  $ ./subx run apps/ex1  # on Linux or BSD or Mac
   $ echo $?
   42
   ```
@@ -80,11 +80,11 @@ messages.
 Emulated runs can generate a trace that permits [time-travel debugging](https://github.com/akkartik/mu/blob/master/tools/browse_trace.readme.md).
 
   ```sh
-  $ ./subx --debug translate init.linux examples/factorial.subx -o examples/factorial
+  $ ./subx --debug translate init.linux apps/factorial.subx -o apps/factorial
   saving address->label information to 'labels'
   saving address->source information to 'source_lines'
 
-  $ ./subx --debug --trace run examples/factorial
+  $ ./subx --debug --trace run apps/factorial
   saving trace to 'last_run'
 
   $ tools/browse_trace last_run  # text-mode debugger UI
@@ -111,14 +111,14 @@ You can use SubX to translate itself. For example, running natively on Linux:
   $ chmod +x hex survey pack assort dquotes tests
 
   # use the generated translator phases to translate SubX programs
-  $ cat init.linux examples/ex1.subx |./tests |./dquotes |./assort |./pack |./survey |./hex > a.elf
+  $ cat init.linux apps/ex1.subx |./tests |./dquotes |./assort |./pack |./survey |./hex > a.elf
   $ chmod +x a.elf
   $ ./a.elf
   $ echo $?
   42
 
   # or, automating the above steps
-  $ ./translate_subx init.linux examples/ex1.subx
+  $ ./translate_subx init.linux apps/ex1.subx
   $ ./a.elf
   $ echo $?
   42
@@ -142,7 +142,7 @@ work on a cloud server.)
   $ sudo apt install util-linux nasm xorriso  # maybe also dosfstools and mtools
   # package up a "hello world" program with a third-party kernel into mu_soso.iso
   # requires sudo
-  $ ./gen_soso_iso init.soso examples/ex6.subx
+  $ ./gen_soso_iso init.soso apps/ex6.subx
   # try it out
   $ qemu-system-i386 -cdrom mu_soso.iso
   ```
@@ -154,7 +154,7 @@ kernel; that number will gradually go down.)
 
   ```sh
   $ sudo apt install build-essential flex bison wget libelf-dev libssl-dev xorriso
-  $ ./gen_linux_iso init.linux examples/ex6.subx
+  $ ./gen_linux_iso init.linux apps/ex6.subx
   $ qemu-system-x86_64 -m 256M -cdrom mu.iso -boot d
   ```
 
@@ -299,7 +299,7 @@ and digest it:
 
 Here's a more meaty example:
 
-<img alt='examples/ex3.subx' src='html/ex3.png'>
+<img alt='apps/ex3.subx' src='html/ex3.png'>
 
 This program sums the first 10 natural numbers. By convention I use horizontal
 tabstops to help read instructions, dots to help follow the long lines,
@@ -313,8 +313,8 @@ like decimal numbers.
 Try running this example now:
 
 ```sh
-$ ./subx translate init.linux examples/ex3.subx -o examples/ex3
-$ ./subx run examples/ex3
+$ ./subx translate init.linux apps/ex3.subx -o apps/ex3
+$ ./subx run apps/ex3
 $ echo $?
 55
 ```
@@ -322,7 +322,7 @@ $ echo $?
 If you're on Linux you can also run it natively:
 
 ```sh
-$ ./examples/ex3
+$ ./apps/ex3
 $ echo $?
 55
 ```
@@ -413,13 +413,14 @@ SubX will transparently copy it to the `data` segment and replace it with its
 address. Strings are the only place where a SubX word is allowed to contain
 spaces.
 
-That should be enough information for writing SubX programs. The `examples/`
-directory provides some fodder for practice, giving a more gradual introduction
-to SubX features. This repo includes the binary for all examples. At any
-commit, an example's binary should be identical bit for bit with the result of
-translating the corresponding `.subx` file. The binary should also be natively
-runnable on a Linux system running on Intel x86 processors, either 32- or
-64-bit. If either of these invariants is broken it's a bug on my part.
+That should be enough information for writing SubX programs. The `apps/`
+directory provides some fodder for practice in the `apps/ex*` files, giving a
+more gradual introduction to SubX features. This repo includes binaries for
+all examples. At any commit, an example's binary should be identical bit for
+bit with the result of translating the corresponding `.subx` file. The binary
+should also be natively runnable on a Linux system running on Intel x86
+processors, either 32- or 64-bit. If either of these invariants is broken it's
+a bug on my part.
 
 ## Running
 
diff --git a/apps/Readme.md b/apps/Readme.md
index 1861d949..1e1a5685 100644
--- a/apps/Readme.md
+++ b/apps/Readme.md
@@ -1,2 +1,11 @@
-Larger programs than in the examples/ subdirectory, combining the techniques
-demonstrated there.
+Some apps written in SubX and Mu, in 3 categories:
+
+* `ex*`: small stand-alone examples that don't need any of the shared code at
+  the top-level. They each have a simple pedagogical goal. Try these first.
+
+* Code unique to phases of our build toolchain:
+  * Core SubX: `hex`, `survey`, `pack`, `dquotes`, `assort`, `tests`
+  * Syntax sugar for SubX: `sigils`, `calls`, `braces`
+  * More ambitious translator for a memory-safe language (in progress): `mu`
+
+* Miscellaneous test programs.
diff --git a/examples/ex1 b/apps/ex1
index 5f17bc66..5f17bc66 100755
--- a/examples/ex1
+++ b/apps/ex1
Binary files differdiff --git a/examples/ex1.subx b/apps/ex1.subx
index 5558d310..5558d310 100644
--- a/examples/ex1.subx
+++ b/apps/ex1.subx
diff --git a/examples/ex10 b/apps/ex10
index cb8973fe..cb8973fe 100755
--- a/examples/ex10
+++ b/apps/ex10
Binary files differdiff --git a/examples/ex10.subx b/apps/ex10.subx
index c091fe52..c091fe52 100644
--- a/examples/ex10.subx
+++ b/apps/ex10.subx
diff --git a/examples/ex11 b/apps/ex11
index 1cb1aa5c..1cb1aa5c 100755
--- a/examples/ex11
+++ b/apps/ex11
Binary files differdiff --git a/examples/ex11.subx b/apps/ex11.subx
index b235927d..b235927d 100644
--- a/examples/ex11.subx
+++ b/apps/ex11.subx
diff --git a/examples/ex12 b/apps/ex12
index 80e5deeb..80e5deeb 100755
--- a/examples/ex12
+++ b/apps/ex12
Binary files differdiff --git a/examples/ex12.subx b/apps/ex12.subx
index 9c67f909..9c67f909 100644
--- a/examples/ex12.subx
+++ b/apps/ex12.subx
diff --git a/examples/ex2 b/apps/ex2
index 5e0c1be1..5e0c1be1 100755
--- a/examples/ex2
+++ b/apps/ex2
Binary files differdiff --git a/examples/ex2.subx b/apps/ex2.subx
index 8df4c62c..8df4c62c 100644
--- a/examples/ex2.subx
+++ b/apps/ex2.subx
diff --git a/examples/ex3 b/apps/ex3
index af787c11..af787c11 100755
--- a/examples/ex3
+++ b/apps/ex3
Binary files differdiff --git a/examples/ex3.subx b/apps/ex3.subx
index f6f8c17d..f6f8c17d 100644
--- a/examples/ex3.subx
+++ b/apps/ex3.subx
diff --git a/examples/ex4 b/apps/ex4
index 35ade1ee..35ade1ee 100755
--- a/examples/ex4
+++ b/apps/ex4
Binary files differdiff --git a/examples/ex4.subx b/apps/ex4.subx
index 78a97433..78a97433 100644
--- a/examples/ex4.subx
+++ b/apps/ex4.subx
diff --git a/examples/ex5 b/apps/ex5
index 805cadc3..805cadc3 100755
--- a/examples/ex5
+++ b/apps/ex5
Binary files differdiff --git a/examples/ex5.subx b/apps/ex5.subx
index bacef8d4..bacef8d4 100644
--- a/examples/ex5.subx
+++ b/apps/ex5.subx
diff --git a/examples/ex6 b/apps/ex6
index 06fdfd7b..06fdfd7b 100755
--- a/examples/ex6
+++ b/apps/ex6
Binary files differdiff --git a/examples/ex6.subx b/apps/ex6.subx
index 42612578..42612578 100644
--- a/examples/ex6.subx
+++ b/apps/ex6.subx
diff --git a/examples/ex7 b/apps/ex7
index 0a535d45..0a535d45 100755
--- a/examples/ex7
+++ b/apps/ex7
Binary files differdiff --git a/examples/ex7.subx b/apps/ex7.subx
index 1c551cad..1c551cad 100644
--- a/examples/ex7.subx
+++ b/apps/ex7.subx
diff --git a/examples/ex8 b/apps/ex8
index 78f1773d..78f1773d 100755
--- a/examples/ex8
+++ b/apps/ex8
Binary files differdiff --git a/examples/ex8.subx b/apps/ex8.subx
index 0e44a883..0e44a883 100644
--- a/examples/ex8.subx
+++ b/apps/ex8.subx
diff --git a/examples/ex9 b/apps/ex9
index 5140cf68..5140cf68 100755
--- a/examples/ex9
+++ b/apps/ex9
Binary files differdiff --git a/examples/ex9.subx b/apps/ex9.subx
index 443e443e..443e443e 100644
--- a/examples/ex9.subx
+++ b/apps/ex9.subx
diff --git a/edit b/edit
index dc434f58..400ab370 100755
--- a/edit
+++ b/edit
@@ -12,12 +12,7 @@ fi
 
 if [[ $EDITOR == *'vim'* ]]
 then
-  LOCAL_SETTINGS='-S vimrc.vim'
-fi
-
-if [[ $1 == 'ex'* ]]
-then
-  eval $EDITOR $LOCAL_SETTINGS examples/$1.subx
+  $EDITOR -S vimrc.vim apps/$1.subx
 else
-  eval $EDITOR $LOCAL_SETTINGS apps/$1.subx
+  $EDITOR              apps/$1.subx
 fi
diff --git a/examples/Readme.md b/examples/Readme.md
deleted file mode 100644
index d4bb1ff5..00000000
--- a/examples/Readme.md
+++ /dev/null
@@ -1,6 +0,0 @@
-Small example programs, each with a simple pedagogical goal.
-
-They also help to validate SubX instruction semantics against native x86
-hardware. For example, loading a single byte to a register would for some time
-clear the rest of the register. This behavior was internally consistent with
-unit tests. It took running an example binary natively to catch the discrepancy.
diff --git a/html/examples/ex1.subx.html b/html/apps/ex1.subx.html
index c4105769..c4105769 100644
--- a/html/examples/ex1.subx.html
+++ b/html/apps/ex1.subx.html
diff --git a/html/examples/ex10.subx.html b/html/apps/ex10.subx.html
index bcf0e466..bcf0e466 100644
--- a/html/examples/ex10.subx.html
+++ b/html/apps/ex10.subx.html
diff --git a/html/examples/ex11.subx.html b/html/apps/ex11.subx.html
index 47c0b289..47c0b289 100644
--- a/html/examples/ex11.subx.html
+++ b/html/apps/ex11.subx.html
diff --git a/html/examples/ex12.subx.html b/html/apps/ex12.subx.html
index a6b2dc64..a6b2dc64 100644
--- a/html/examples/ex12.subx.html
+++ b/html/apps/ex12.subx.html
diff --git a/html/examples/ex2.subx.html b/html/apps/ex2.subx.html
index c67315e9..c67315e9 100644
--- a/html/examples/ex2.subx.html
+++ b/html/apps/ex2.subx.html
diff --git a/html/examples/ex3.subx.html b/html/apps/ex3.subx.html
index 7c3da099..7c3da099 100644
--- a/html/examples/ex3.subx.html
+++ b/html/apps/ex3.subx.html
diff --git a/html/examples/ex4.subx.html b/html/apps/ex4.subx.html
index 43f5c705..43f5c705 100644
--- a/html/examples/ex4.subx.html
+++ b/html/apps/ex4.subx.html
diff --git a/html/examples/ex5.subx.html b/html/apps/ex5.subx.html
index f5112fa7..f5112fa7 100644
--- a/html/examples/ex5.subx.html
+++ b/html/apps/ex5.subx.html
diff --git a/html/examples/ex6.subx.html b/html/apps/ex6.subx.html
index c8bbdd21..c8bbdd21 100644
--- a/html/examples/ex6.subx.html
+++ b/html/apps/ex6.subx.html
diff --git a/html/examples/ex7.subx.html b/html/apps/ex7.subx.html
index 762bf7ec..762bf7ec 100644
--- a/html/examples/ex7.subx.html
+++ b/html/apps/ex7.subx.html
diff --git a/html/examples/ex8.subx.html b/html/apps/ex8.subx.html
index 1f57fcdf..1f57fcdf 100644
--- a/html/examples/ex8.subx.html
+++ b/html/apps/ex8.subx.html
diff --git a/html/examples/ex9.subx.html b/html/apps/ex9.subx.html
index fbf7b76c..fbf7b76c 100644
--- a/html/examples/ex9.subx.html
+++ b/html/apps/ex9.subx.html
diff --git a/test_apps b/test_apps
index b9b22db1..eaf102e8 100755
--- a/test_apps
+++ b/test_apps
@@ -28,144 +28,144 @@ echo "== translating and running using C++"
 # example programs
 
 echo ex1
-./subx translate init.$OS examples/ex1.subx  -o examples/ex1
-test "$1" = 'record'  ||  git diff --exit-code examples/ex1
+./subx translate init.$OS apps/ex1.subx  -o apps/ex1
+test "$1" = 'record'  ||  git diff --exit-code apps/ex1
 test $EMULATED  &&  {
-  ./subx run examples/ex1  ||  ret=$?
+  ./subx run apps/ex1  ||  ret=$?
   test $ret -eq 42  # life, the universe and everything
 }
 test $NATIVE  &&  {
-  examples/ex1  ||  ret=$?
+  apps/ex1  ||  ret=$?
   test $ret -eq 42  # life, the universe and everything
 }
 
 echo ex2
-./subx translate init.$OS examples/ex2.subx  -o examples/ex2
-test "$1" = 'record'  ||  git diff --exit-code examples/ex2
+./subx translate init.$OS apps/ex2.subx  -o apps/ex2
+test "$1" = 'record'  ||  git diff --exit-code apps/ex2
 test $EMULATED  &&  {
-  ./subx run examples/ex2  ||  ret=$?
+  ./subx run apps/ex2  ||  ret=$?
   test $ret -eq 2  # 1 + 1
 }
 test $NATIVE  &&  {
-  examples/ex2  ||  ret=$?
+  apps/ex2  ||  ret=$?
   test $ret -eq 2  # 1 + 1
 }
 
 echo ex3
-./subx translate init.$OS examples/ex3.subx  -o examples/ex3
-test "$1" = 'record'  ||  git diff --exit-code examples/ex3
+./subx translate init.$OS apps/ex3.subx  -o apps/ex3
+test "$1" = 'record'  ||  git diff --exit-code apps/ex3
 test $EMULATED  &&  {
-  ./subx run examples/ex3  ||  ret=$?
+  ./subx run apps/ex3  ||  ret=$?
   test $ret -eq 55  # 1 + 2 + ... + 10
 }
 test $NATIVE  &&  {
-  examples/ex3  ||  ret=$?
+  apps/ex3  ||  ret=$?
   test $ret -eq 55  # 1 + 2 + ... + 10
 }
 
 echo ex4
-./subx translate init.$OS examples/ex4.subx  -o examples/ex4
-test "$1" = 'record'  ||  git diff --exit-code examples/ex4
+./subx translate init.$OS apps/ex4.subx  -o apps/ex4
+test "$1" = 'record'  ||  git diff --exit-code apps/ex4
 test $EMULATED  &&  {
-  echo a | ./subx run examples/ex4 >ex4.out  ||  true
+  echo a | ./subx run apps/ex4 >ex4.out  ||  true
   test `cat ex4.out` = 'a'
 }
 test $NATIVE  &&  {
-  echo a | examples/ex4 >ex4.out  ||  true
+  echo a | apps/ex4 >ex4.out  ||  true
   test `cat ex4.out` = 'a'
 }
 
 echo ex5
-./subx translate init.$OS examples/ex5.subx  -o examples/ex5
-test "$1" = 'record'  ||  git diff --exit-code examples/ex5
+./subx translate init.$OS apps/ex5.subx  -o apps/ex5
+test "$1" = 'record'  ||  git diff --exit-code apps/ex5
 test $EMULATED  &&  {
-  echo a | ./subx run examples/ex5 >ex5.out  ||  true
+  echo a | ./subx run apps/ex5 >ex5.out  ||  true
   test `cat ex5.out` = 'a'
 }
 test $NATIVE  &&  {
-  echo a | examples/ex5 >ex5.out  ||  true
+  echo a | apps/ex5 >ex5.out  ||  true
   test `cat ex5.out` = 'a'
 }
 
 echo ex6
-./subx translate init.$OS examples/ex6.subx  -o examples/ex6
-test "$1" = 'record'  ||  git diff --exit-code examples/ex6
+./subx translate init.$OS apps/ex6.subx  -o apps/ex6
+test "$1" = 'record'  ||  git diff --exit-code apps/ex6
 test $EMULATED  &&  {
-  ./subx run examples/ex6 >ex6.out  ||  true
+  ./subx run apps/ex6 >ex6.out  ||  true
   test "`cat ex6.out`" = 'Hello, world!'
 }
 test $NATIVE  &&  {
-  examples/ex6 >ex6.out  ||  true
+  apps/ex6 >ex6.out  ||  true
   test "`cat ex6.out`" = 'Hello, world!'
 }
 
 echo ex7
-./subx translate init.$OS examples/ex7.subx  -o examples/ex7
-test "$1" = 'record'  ||  git diff --exit-code examples/ex7
+./subx translate init.$OS apps/ex7.subx  -o apps/ex7
+test "$1" = 'record'  ||  git diff --exit-code apps/ex7
 test $EMULATED  &&  {
-  ./subx run examples/ex7  ||  ret=$?
+  ./subx run apps/ex7  ||  ret=$?
   test $ret -eq 97  # 'a'
 }
 test $NATIVE  &&  {
-  examples/ex7  ||  ret=$?
+  apps/ex7  ||  ret=$?
   test $ret -eq 97  # 'a'
 }
 
 echo ex8
-./subx translate init.$OS examples/ex8.subx  -o examples/ex8
-test "$1" = 'record'  || git diff --exit-code examples/ex8
+./subx translate init.$OS apps/ex8.subx  -o apps/ex8
+test "$1" = 'record'  || git diff --exit-code apps/ex8
 test $EMULATED  &&  {
-  ./subx run examples/ex8 abcd  ||  ret=$?
+  ./subx run apps/ex8 abcd  ||  ret=$?
   test $ret -eq 4  # length('abcd')
 }
 test $NATIVE  &&  {
-  examples/ex8 abcd  ||  ret=$?
+  apps/ex8 abcd  ||  ret=$?
   test $ret -eq 4  # length('abcd')
 }
 
 echo ex9
-./subx translate init.$OS examples/ex9.subx  -o examples/ex9
-test "$1" = 'record'  || git diff --exit-code examples/ex9
+./subx translate init.$OS apps/ex9.subx  -o apps/ex9
+test "$1" = 'record'  || git diff --exit-code apps/ex9
 test $EMULATED  &&  {
-  ./subx run examples/ex9 z x  ||  ret=$?
+  ./subx run apps/ex9 z x  ||  ret=$?
   test $ret -eq 2  # 'z' - 'x'
 }
 test $NATIVE  &&  {
-  examples/ex9 z x  ||  ret=$?
+  apps/ex9 z x  ||  ret=$?
   test $ret -eq 2  # 'z' - 'x'
 }
 
 echo ex10
-./subx translate init.$OS examples/ex10.subx  -o examples/ex10
-test "$1" = 'record'  || git diff --exit-code examples/ex10
+./subx translate init.$OS apps/ex10.subx  -o apps/ex10
+test "$1" = 'record'  || git diff --exit-code apps/ex10
 test $EMULATED  &&  {
-  ./subx run examples/ex10 abc abc  ||  ret=$?
+  ./subx run apps/ex10 abc abc  ||  ret=$?
   test $ret -eq 1  # equal
-  ./subx run examples/ex10 abc abcd  # 0; not equal
+  ./subx run apps/ex10 abc abcd  # 0; not equal
 }
 test $NATIVE  &&  {
-  examples/ex10 abc abc  ||  ret=$?
+  apps/ex10 abc abc  ||  ret=$?
   test $ret -eq 1  # equal
-  examples/ex10 abc abcd  # 0; not equal
+  apps/ex10 abc abcd  # 0; not equal
 }
 
 echo ex11
-./subx translate init.$OS examples/ex11.subx  -o examples/ex11
-test "$1" = 'record'  || git diff --exit-code examples/ex11
+./subx translate init.$OS apps/ex11.subx  -o apps/ex11
+test "$1" = 'record'  || git diff --exit-code apps/ex11
 test $EMULATED  &&  {
-  ./subx run examples/ex11
+  ./subx run apps/ex11
   echo
 }
 test $NATIVE  &&  {
-  examples/ex11
+  apps/ex11
   echo
 }
 
 echo ex12
-./subx translate init.$OS examples/ex12.subx  -o examples/ex12
-test "$1" = 'record'  || git diff --exit-code examples/ex12
-test $EMULATED  &&  ./subx run examples/ex12  # final byte of mmap'd address is well-nigh guaranteed to be 0
-test $NATIVE  &&  examples/ex12
+./subx translate init.$OS apps/ex12.subx  -o apps/ex12
+test "$1" = 'record'  || git diff --exit-code apps/ex12
+test $EMULATED  &&  ./subx run apps/ex12  # final byte of mmap'd address is well-nigh guaranteed to be 0
+test $NATIVE  &&  apps/ex12
 
 # Larger apps that use the standard library.
 
@@ -304,8 +304,8 @@ echo "== translating using SubX (native only)"
 for n in `seq 1 12`
 do
   echo ex$n
-  ./translate_subx init.$OS examples/ex$n.subx
-  diff examples/ex$n a.elf
+  ./translate_subx init.$OS apps/ex$n.subx
+  diff apps/ex$n a.elf
 done
 
 # Larger apps that use the standard library.
diff --git a/vimrc.vim b/vimrc.vim
index 0200e01c..c01ab5c5 100644
--- a/vimrc.vim
+++ b/vimrc.vim
@@ -44,15 +44,7 @@ else
 endif
 
 function! EditSubx(cmd, arg)
-  exec "silent! " . a:cmd . " " . SubxPath(a:arg)
-endfunction
-
-function! SubxPath(arg)
-  if a:arg =~ "^ex"
-    return "examples/" . a:arg . ".subx"
-  else
-    return "apps/" . a:arg . ".subx"
-  endif
+  exec "silent! " . a:cmd . " apps/" . a:arg . ".subx"
 endfunction
 
 " we often want to crib lines of machine code from other files