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possible syntax for mole ("M0 Overlay LanguagE")
I propose that we have 5 types; INSP for registers and cs, which is a C-like
string. (This probably won't be exactly like a C-string, but close enough that
C code can use it if needed.)
registers: I, N, S, P
primitive string: cs
*constant values*
This describes what kind of constants can be used in mole code.
int: [1-9]\d*
float: ...
hex: 0[xX][0-9a-fA-F]+
octal: 0[0-7]+
string: "[...]" (with escapes)
*compile-time constants*
*working with strings*
Strings pretend to be 0-indexed. They actually also store their length and
encoding as the first five values. The length is stored as a 4B int and the
encoding is stored in one byte, with 3 unused bytes for padding. The string
for "hello, worlds?" would look as follows in memory:
0x0 0x4 0x8 0xA 0x10 0x14
|0x0|0x0|0x0|0xC|0x0|0x0|0x0|0x1| h | e | l | l | o | , | | w | o | r | l | d | s | ? |\0 |
size encoding 0x0 0x4 0x8 0xA
Once a struct is defined, it can be used wherever any other type can be used.
Struct members are accessed using the '.' notation, as in C. sizeof() can be
used to determine the number of bytes required by the struct. This is similar
to C, except that sizeof() is purely a compile-time construct and can not be
used to calculate the length of an array.
struct {
I int_thingy;
N n_thingy;
} struct_thingy;
var I quux;
#XXX: does this do any kind of allocation or just say "when you're looking at st, it has this structure"
var struct_thingy st;
st = m0::sys_alloc sizeof(struct_thingy);
st.int_thingy = 39292934;
st.n_thingy = 332.66;
Chunks are similar to functions. They have a constants table, a metadata table
and a bytecode segment. Values can be added to the constants table by
declaring a value with the keyword "const". Annotations may be added
automatically by the mole compiler and can also be added manually with the .ann
"key" "value" syntax.
chunk main (I a1, I a2, I a3) {
const I stdout 1;
const cs hello "ohai. im in ur m0";
// annotation for the right file will be added by m1 compiler
m0::print_i stdout, hello;
var I i_thingy;
i_thingy += a3++;
c::fprintf(stdout, "asdfw %d\n", i_thingy);
call_chunk "chunk_name", arg_array;
*composed ops*
mole supports syntax to create composed ops which behave similarly to built-in
M0 ops. The syntax is similar to chunnks with a few differences. Composed ops
are declared using the "composed"keyword and do not have an explicit return
statement. They may take an arbitrary number of arguments. Variables may be
declared in composed ops as in functions. composed ops are similar to inlined
functions in C.
composed init_cf(P new_cf, I retpc_label) {
I cf_size = 256;
I flags = 0;
new_cf = m0::gc_alloc cf_size, flags;
new_cf[INTERP] = cf[INTERP];
new_cf[CHUNK] = cf[CHUNK];
new_cf[CONSTS] = cf[CONSTS];
new_cf[MDS] = cf[MDS];
new_cf[BCS] = cf[BCS];
new_cf[PCF] = cf[CF];
new_cf[CF] = new_cf;
new_cf[EH] = 0;
new_cf[RETPC] = 0;
new_cf[SPILLCF] = 0;
RETPC = retpc_label;
new_cf[PC] = post_set;
CF = new_cf;
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