Indentation control while developing a small python like language

Question

I\'m developing a small python like language using flex, byacc (for lexical and parsing) and C++, but i have a few questions regarding scope control.

just as python it u

Answer 1

I am currently implementing a programming language rather similar to this (including the multilevel break oddly enough). My solution was to have the tokenizer emit indent and dedent tokens based on indentation. Eg:

while 1: # colons help :)
    print('foo')
    break 1

becomes:

["while", "1", ":",
    indent,
    "print", "(", "'foo'", ")",
    "break", "1",
    dedent]

It makes the tokenizer's handling of '\n' somewhat complicated though. Also, i wrote the tokenizer and parser from scratch, so i'm not sure whether this is feasable in lex and yacc.

Edit:

Semi-working pseudocode example:

level = 0
levels = []
for c = getc():
    if c=='\n':
        emit('\n')
        n = 0
        while (c=getc())==' ':
            n += 1
        if n > level:
            emit(indent)
            push(levels,n)
        while n < level:
            emit(dedent)
            level = pop(levels)
            if level < n:
                error tokenize
        # fall through
    emit(c) #lazy example

Answer 2

Very interesting exercise. Can't you use the end keyword to check when the scope ends?

On a different note, I have never seen a language that allows you to break out of several nested loops at once. There may be a good reason for that...