rust/src/libcore/bool.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.


//! Boolean logic

use option::{None, Option, Some};
use from_str::FromStr;

#[cfg(notest)] use cmp;

/// Negation / inverse
pub pure fn not(v: bool) -> bool { !v }

/// Conjunction
pub pure fn and(a: bool, b: bool) -> bool { a && b }

/// Disjunction
pub pure fn or(a: bool, b: bool) -> bool { a || b }

/**
 * Exclusive or
 *
 * Identical to `or(and(a, not(b)), and(not(a), b))`
 */
pub pure fn xor(a: bool, b: bool) -> bool { (a && !b) || (!a && b) }

/// Implication in the logic, i.e. from `a` follows `b`
pub pure fn implies(a: bool, b: bool) -> bool { !a || b }

/// true if truth values `a` and `b` are indistinguishable in the logic
pub pure fn eq(a: bool, b: bool) -> bool { a == b }

/// true if truth values `a` and `b` are distinguishable in the logic
pub pure fn ne(a: bool, b: bool) -> bool { a != b }

/// true if `v` represents truth in the logic
pub pure fn is_true(v: bool) -> bool { v }

/// true if `v` represents falsehood in the logic
pub pure fn is_false(v: bool) -> bool { !v }

/// Parse logic value from `s`
impl FromStr for bool {
    static pure fn from_str(s: &str) -> Option<bool> {
        if s == "true" {
            Some(true)
        } else if s == "false" {
            Some(false)
        } else {
            None
        }
    }
}

/// Convert `v` into a string
pub pure fn to_str(v: bool) -> ~str { if v { ~"true" } else { ~"false" } }

/**
 * Iterates over all truth values by passing them to `blk` in an unspecified
 * order
 */
pub fn all_values(blk: fn(v: bool)) {
    blk(true);
    blk(false);
}

/// converts truth value to an 8 bit byte
pub pure fn to_bit(v: bool) -> u8 { if v { 1u8 } else { 0u8 } }

#[cfg(notest)]
impl cmp::Eq for bool {
    pure fn eq(&self, other: &bool) -> bool { (*self) == (*other) }
    pure fn ne(&self, other: &bool) -> bool { (*self) != (*other) }
}

#[test]
pub fn test_bool_from_str() {
    use from_str::FromStr;

    do all_values |v| {
        fail_unless!(Some(v) == FromStr::from_str(to_str(v)))
    }
}

#[test]
pub fn test_bool_to_str() {
    fail_unless!(to_str(false) == ~"false");
    fail_unless!(to_str(true) == ~"true");
}

#[test]
pub fn test_bool_to_bit() {
    do all_values |v| {
        fail_unless!(to_bit(v) == if is_true(v) { 1u8 } else { 0u8 });
    }
}

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