▁code ▁to ▁be ▁generated . ▁ ▁Thus ▁T B NF ▁defines ▁the ▁complete ▁translation ▁process ▁from ▁input ▁source ▁code ▁to ▁intermediate ▁code . ▁ ▁Spec ification ▁of ▁the ▁output ▁intermediate ▁code ▁is ▁optional , ▁in ▁which ▁case ▁you ▁will ▁still ▁get ▁automatic ▁A ST ▁creation ▁and ▁have ▁the ▁ability ▁to ▁define ▁its ▁structure ▁in ▁the ▁grammar . ▁ ▁The ▁T B NF ▁concept ▁was ▁first ▁published ▁in ▁April ▁ 2 0 0 6 ▁in ▁a ▁paper ▁at ▁S IG PL AN ▁Notices , ▁a ▁special ▁interest ▁group ▁of ▁the ▁AC M . ▁ ▁Here ▁is ▁a ▁sample ▁grammar ▁specified ▁in ▁T B NF : ▁▁ ▁/* ▁T B NF ▁Gram mar ▁for ▁a ▁simple ▁language . ▁▁▁▁▁ ▁Five ▁node ▁arguments ▁are ▁used ▁in ▁this ▁grammar ▁to ▁avoid ▁having ▁to ▁create ▁node ▁actions . ▁*/ ▁/* ▁Input ▁Tok ens . ▁*/ ▁▁▁▁ ▁< error > ▁▁▁▁▁▁▁ ▁=> ▁error () ▁; ▁▁▁▁▁ ▁< identifier > ▁▁ ▁=> ▁lookup (); ▁ ▁// ▁Look up ▁& ▁store ▁in ▁symbol ▁table . ▁▁▁ ▁< integer > ▁▁▁▁▁ ▁=> ▁lookup (); ▁ ▁// ▁Look up ▁& ▁store ▁in ▁symbol ▁table . ▁▁▁▁ ▁< e of > ▁▁▁▁▁▁▁▁▁ ▁; ▁ ▁/* ▁Oper ator ▁preced ence . ▁*/ ▁▁▁▁ ▁{ ▁' == ' ▁' ! =' ▁} ▁ ▁<< ▁▁▁ ▁// ▁Low est ▁priority . ▁▁▁▁▁▁▁ ▁{ ▁' +' ▁ ▁'- ' ▁ ▁} ▁ ▁<< ▁▁▁▁▁▁▁▁▁▁▁▁ ▁{ ▁' * ' ▁ ▁'/ ' ▁ ▁} ▁ ▁<< ▁▁▁ ▁// ▁High est ▁priority . ▁ ▁/* ▁Produ ctions . ▁*/ ▁▁▁▁