# Toy lisp interpreter
#
# Current status: repeatedly reads line of text and prints it out.
#
# To run:
#   $ ./ntranslate 0*.subx apps/subx-common.subx apps/mulisp.subx
#   $ ./a.elf
#   42
#   => 42
#   ^D
#   $
#
# Or, for emulated mode (veeery slow):
#   $ cat 0*.subx apps/mulisp.subx  |  ./subx run apps/desugar > a.desugar
#   $ ./subx translate a.desugar -o a.elf

== code

Entry:  # run tests if necessary, a REPL if not
    # . prolog
    89/<- %ebp 4/r32/esp
    # initialize heap
    (new-segment Heap-size Heap)
    # if (argc <= 1) goto run-main
    81 7/subop/compare *ebp 1/imm32
    7e/jump-if-lesser-or-equal $run-main/disp8
    # if (argv[1] != "test")) goto run-main
    (kernel-string-equal? *(ebp+8) "test")  # => eax
    3d/compare-eax-and 0/imm32
    74/jump-if-equal $run-main/disp8
    #
    (run-tests)
    # syscall(exit, *Num-test-failures)
    8b/-> *Num-test-failures 3/r32/ebx
    eb/jump $main:end/disp8
$run-main:
    (repl Stdin Stdout)
    # syscall(exit, 0)
    bb/copy-to-ebx 0/imm32
$main:end:
    b8/copy-to-eax 1/imm32/exit
    cd/syscall 0x80/imm8

repl:  # in : (address buffered-file), out : (address buffered-file) -> <void>
    # . prolog
    55/push-ebp
    89/<- %ebp 4/r32/esp
    # . save registers
    51/push-ecx
    # var s/ecx : (address stream)
    81 5/subop/subtract %esp 0x200/imm32
    68/push 0x200/imm32/size
    68/push 0/imm32/read
    68/push 0/imm32/write
    89/<- %ecx 4/r32/esp
$repl:loop:
    (clear-stream %ecx)
    (read-line-buffered Stdin %ecx)
    # if (s->write == 0) break
    81 7/subop/compare *ecx 0/imm32
    74/jump-if-equal $repl:end/disp8
    # write(s)
    (write-buffered Stdout "=> ")
    (write-stream-data Stdout %ecx)
    (flush Stdout)
    # loop
    eb/jump $repl:loop/disp8
$repl:end:
    # . reclaim locals
    81 0/subop/add %esp 0x20c/imm32
    # . restore registers
    59/pop-to-ecx
    # . epilog
    89/<- %esp 5/r32/ebp
    5d/pop-to-ebp
    c3/return