Function setFloatString [src]

Set a Rational from a string of the form A/B where A and B are base-10 integers.
Prototype

pub fn setFloatString(self: *Rational, str: []const u8) !void
Parameters

self: *Rationalstr: []const u8
Source

  pub fn setFloatString(self: *Rational, str: []const u8) !void {
    // TODO: Accept a/b fractions and exponent form
    if (str.len == 0) {
        return error.InvalidFloatString;
    }

    const State = enum {
        Integer,
        Fractional,
    };

    var state = State.Integer;
    var point: ?usize = null;

    var start: usize = 0;
    if (str[0] == '-') {
        start += 1;
    }

    for (str, 0..) |c, i| {
        switch (state) {
            State.Integer => {
                switch (c) {
                    '.' => {
                        state = State.Fractional;
                        point = i;
                    },
                    '0'...'9' => {
                        // okay
                    },
                    else => {
                        return error.InvalidFloatString;
                    },
                }
            },
            State.Fractional => {
                switch (c) {
                    '0'...'9' => {
                        // okay
                    },
                    else => {
                        return error.InvalidFloatString;
                    },
                }
            },
        }
    }

    // TODO: batch the multiplies by 10
    if (point) |i| {
        try self.p.setString(10, str[0..i]);

        const base = IntConst{ .limbs = &[_]Limb{10}, .positive = true };
        var local_buf: [@sizeOf(Limb) * Int.default_capacity]u8 align(@alignOf(Limb)) = undefined;
        var fba = std.heap.FixedBufferAllocator.init(&local_buf);
        const base_managed = try base.toManaged(fba.allocator());

        var j: usize = start;
        while (j < str.len - i - 1) : (j += 1) {
            try self.p.ensureMulCapacity(self.p.toConst(), base);
            try self.p.mul(&self.p, &base_managed);
        }

        try self.q.setString(10, str[i + 1 ..]);
        try self.p.add(&self.p, &self.q);

        try self.q.set(1);
        var k: usize = i + 1;
        while (k < str.len) : (k += 1) {
            try self.q.mul(&self.q, &base_managed);
        }

        try self.reduce();
    } else {
        try self.p.setString(10, str[0..]);
        try self.q.set(1);
    }
}  