Function add

test/internal/casting.js:123–125

(value1, value2)

function handleCastingFloat(mode) {
  const gpu = new GPU({ mode });
  function add(value1, value2) {
    return value1 + value2;
  }
  gpu.addFunction(add, {
    argumentTypes: ['Float', 'Float'],
    returnType: 'Float'