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SCT Implementation Appendix SCT implementation In this appendix code is presented for an implementation of SCT evaluat ion together with t he grammar definit ions from t his book. T he implement ation is separated into three programs. The first is an awk script used to generate Standard ML code for sequence assign­ ments. The second is a Standard ML program providing t he SCT evaluation routine. The third is a Standard ML program containing the grammar definitions. Information on using t hese programs is also given. A wk script to generate sequence assignments { print " (*the as signment data t ype*) " for (i = 1; i <= NF ; i++) printf("'l,s%s:fol list%s", i == 1 ? \ ''type assn= { '' : '''' , $ i , i < NF ? "}\n\n" ) print '' (* the empty assignment *) '' for (i = 1; i <= NF; i ++) printf ( "%s%s=nil %s ", i == 1 ? \ "val assnO:assn = { " : 11 11 , $i, i < NF ? "}\ n\n") print '' ( * t he err or assi gnment *) u for (i = 1; i <= NF ; i ++) printf("%s%s= [Error \"%s error\"]%s", i == 1 ? \ "val assnError: assn = {" : "", $i, $i , i < NF? ", " : "}\ n\ n") print '' (* v returns t he sequenc e v alue g assigns t o name *) '' for (i = 1; i <= NF; i ++) printf("%s\"%s \ " => #%s g%s " , i == 1? \ "f un v (name : st ring, g :assn):fol list =\n (case name\n of \ $i , $i, i < NF ? " I " : " I _ => nil)\n\n" ) 205 206 THE SEMANTICS OF GRAMMATICAL DEPENDENCIES print"(* vtop returns the frontmost value of the s equence g assigns name *) " print "fun vtop (name:string, g:assn) :fol _,, pri nt '' if v ( name, g) = nil'' print then Error (name-\" error\") else hd (v (name, g) ) \ n" print "(* vend returns t he endmos t value of the s equence g assi gns t o name *) " print "fun vend (name:string, g:assn) :fol _,, print if v ( name , g) = nil'' print " then Error (name-\" error \ ") else hd (rev ( v (name , g)))\n" print '' (* vtl returns the sequence value g assigns t o name *)" print "(* minus the frontmost value *)" print "fun vtl (name: string, g :assn) :fol lis t=" print '' if v (name, g) = nil'' print " then [Error (name-\" error\ ") ] else tl (v (name, g) )\n" print '' (* vrevtlrev returns the s equence value g assigns t o name *)" print '' (* minus the endmost v alue *)" print "fun vrevt lrev (name:string , g : assn) :fol list=" print " if v ( name, g) =nil t hen [Er r or (n ame-\" error\") ] " print " el s e rev (tl (rev (v (name , g) ) ))\n" print '' ( * pop retur ns s e quence a ssi gnment g but with the front most val ue *) '' print '' ( * a s signed t o name remo v e d print ''fun pop (name: string, (g, str) : assn * string) : assn * string =" print " if g = assnError then (g, s t r) else" print if vtl (name, g) = [Error (name-\" error\ ") ] " print " then (assnError , (name- \ " error , no pop\") ) else (case name" for (i = 1 ; i <= NF; i ++) { print f ( "%s\"%s\ 11 => ({ " , i == 1 ? 11 of 11 : " I " $ i ) for ( j = 1; j <= NF ; j++) printf("%s=%s g ) %s", $j, i == j ? "vtl (name,": 11 (# "$j , j < NF? 11 , n 11 11 ) printf("'l.s", i < NF? "}, str)\n " : \ "}, str)\n I _ => (assnError , \ "no \ " -name- \" name, no pop\")\n )\n\ n" ) } print " (* endpop r eturns sequence assignment g but wi th the endmo st va lue*) " print '' (* as s i gne d to name r emoved *) " pr int "f un e ndpop (name: s tring , (g , str ) :assn * string ) :assn * string=" print " if g = assnError then (g, str) else" print if vrevtlrev (name, g) = [Error (name-\" error\ ")]" print " then (a ssnError, (name-\ " error, no endpop\") ) else (case name" for (i = 1 ; i <= NF; i ++ ) { printf("/,s \"%s \ " => ({", i == 1 ? " of " II I " $ i ) for (j = 1 ; j <= NF; j++) printf ( "%s =% s g)%s " , $j , i == j ? \ "vr evtlrev (name .": ''(#"$j, j < NF ? " : "") printf("'l.s" , i < NF ? "}, str)\n " : \ ''} , s tr) \n I _ => ( assnError, \"no \ '' "' name "' \ " name, no endpop\" ) \n )\n\n11 ) } .
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