repro.zig

const std = @import("std");
const fmt = std.fmt;

const Parser = struct {
    input: []const u8,
    ch: u8,
    pos: usize,
    len: usize,

    fn init(input: []const u8) Parser {
        return Parser{
            .input = input,
            .ch = input[0],
            .pos = 0,
            .len = input.len,
        };
    }

    fn parse_factor(self: *Parser) !f64 {
        var res: f64 = 0.0;
        if (self.ch == '0') {
            return self.parse_factor();
        }
        else if (self.ch == '1') {
            return -self.parse_factor();
        }

        if (true) {
            res = try fmt.parseFloat(f64, self.input[0..self.len-1]);
        }
        else {
            return res;
        }
        return res;
        
    }
};

fn eval(input: []u8) !f64 {
    var p = Parser.init(input);
    return try p.parse_factor();
}

pub fn main() !void {
    const input = "100"[0..];
    var p = Parser.init(input);
    _ = try p.parse_factor();
}