Stevia: Human-readable auto-layout in code(github.com)

    [box mas_makeConstraints:^(MASConstraintMaker* make) {
        make.width.height.equalTo(50);
        make.center.equalTo(self.view);    
    }];

    constrain(button1, button2) { button1, button2 in
        button1.right == button2.left - 12
    }

    [box.widthAnchor constraintEqualToConstant:50].active = YES;
    [box.centerAnchor constrantEqualToAnchor:self.view.centerAnchor].active = YES;

    [self addConstraints:box.anchorWidth == 50];
    [self addConstraints:box.anchorHeight == 50];
    [self addConstraints:box.anchorCenterX == self.view.anchorCenterX];
    [self addConstraints:box.anchorCenterY == self.view.anchorCenterY];