[math_proportion]

Description

This tag accepts 4 values, representing 2 proportional ratios in the order given. ("A is to B as X is to Y.") Three of the given values must be integers, and the fourth must be a string, such as 'x', representing the missing value. The tag determines the value of x with a simple cross-multiply and divide operation.

Sample Usage

math_proportion(12,63,'x',345);

-> 65

Source Code

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define_tag(
	'proportion',
	-namespace='math_',
	-priority='replace',
	-description='Finds missing value in basic cross-multiply and divide operation.'
);
	fail_if(
		params->size != 4,
		-1,
		'[math_proportion] requires 4 values (3 integers and an x).'
	);
	
	local('items') = array('a','b','x','y');
	
	iterate(params, local('i'));
		local(#items->get(loop_count)) = #i;
		#i->isa('string') ? local('missing') = #items->get(loop_count);
	/iterate;
	
	select(#missing);
		case('a');
			local('out') = (#b * #x) / #y;
		case('b');
			local('out') = (#a * #y) / #x;
		case('x');
			local('out') = (#a * #y) / #b;
		case('y');
			local('out') = (#b * #x) / #a;
	/select;
	
	return(#out);
/define_tag;

Related Tags

• image_scaleDisplay
• image_scalewithin

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