GARBAGESCRIPT

compiler.py

instructions = []

f = open("input.grs", "r")
src = str(f.read())
f.close()

def var_emit(line):
    name = line[1:].strip()
    instructions.append(["MAKEVAR", name])

def load_emit(line):
    val = line[1:].strip()
    instructions.append(["LOAD", val])

def call_emit(line):
    instructions.append(["CALL", line[1:].strip()])

def defn_emit(line):
    instructions.append(["DEFN"])

def return_emit(line):
    instructions.append(["RETURN"])

newsrc = ""

# preporcess
for line in src.replace("::", "\n").split("\n"):
    line = line.strip()
    if len(line) < 1:
        continue
    if line[0] == '#':
        l = line[1:].split(" ")
        if l[0].startswith("use"):
            f = open(l[1].strip(), "r")
            newsrc += f.read()+"\n"
            f.close()
    else:
        newsrc += line + "\n"

src = newsrc
line_no = 1


for line in src.replace("::", "\n").split("\n"):
    line = line.strip()
    if len(line) < 1:
        continue
    if line[0] == '\\':
        var_emit(line)
    elif line[0] == '\'':
        load_emit(line)
    elif line[0] == '%':
        instructions.append(["LABEL", line[1:].strip()])
    elif line[0] == '$':
        call_emit(line)
    elif line.startswith("?"):
        instructions.append(["IF", line[1:].strip()])
    elif line.startswith("{"):
        defn_emit(line)
    elif line.startswith("}") or line.startswith("return"):
        return_emit(line)
    elif line[0] == '*':
        continue
    else:
        raise Exception("Invalid prefix at line {}".format(line_no))
    line_no += 1

decls = {}
fns = {}
load = None
stack = [] 

pos = 0
for instr in instructions:
    if instr[0] == "LOAD":
        load = instr[1]
    if instr[0] == "DEFN":
        fns[load.strip()] = pos+1 

    pos += 1

load = None
#print(instructions)
pos = fns["main"]
while pos < len(instructions):
    instr = instructions[pos]
    #print(">>", pos, "\t", instr, stack)
    if instr[0] == "LOAD":
        load = instr[1]
    elif instr[0] == "MAKEVAR":
        decls[instr[1]] = load
    elif instr[0] == "IF":
        if load:
            pos += 1
            continue
        npos = pos
        for instruc in instructions[pos:]:
            if instruc[0] == "LABEL" and instruc[1] == instr[1]:
                pos = npos
                break
            npos += 1
        else:
            raise Exception("label "+instr[1]+" not found!")
    elif instr[0] == "RETURN":
        if len(stack) > 0:
            pos = stack.pop()
        else:
            break
    elif instr[0] == "CALL":
        if instr[1] == "assembly":
            exec(load)
        else:
            stack.append(pos)
            pos = fns[instr[1]]
            continue
    pos += 1

input.grs

* This prints something *

#use std.grs

'main :: {
    $false :: ?if
        'Hello world :: $print
    %if :: ?if
        'Hello world :: $print
    %if 
}

std.grs

* Printing *
'print :: {
    \arg
    *--------------------------------*
    'print(decls['arg']) :: $assembly
}

* Discards *
'$ :: {
    'load = None :: $assembly
}

'true :: {
    'load = True :: $assembly
}

'false :: {
    'load = False :: $assembly
}