diff --git a/examples/ties.c b/examples/ties.c
new file mode 100644
index 0000000000000000000000000000000000000000..b8cc9fd9216a192cef85dc897a40096c135fc20a
--- /dev/null
+++ b/examples/ties.c
@@ -0,0 +1,331 @@
+//
+// Created by Mikael Vejdemo Johansson on 4/7/15.
+//
+// Intention: read in a parser, generate the system of equations for its
+// generating functions
+//
+
+#include <inttypes.h>
+#include "../src/backends/contextfree.h"
+#include "../src/backends/lr.h"
+#include <stdio.h>
+
+static const char *nonterminal_name(const HCFGrammar *g, const HCFChoice *nt)
+{
+ static char buf[16] = {0}; // 14 characters in base 26 are enough for 64 bits
+
+ // find nt's number in g
+ size_t n = (uintptr_t)h_hashtable_get(g->nts, nt);
+
+ // NB the start symbol (number 0) is always "A".
+ int i;
+ for(i=14; i>=0 && (n>0 || i==14); i--) {
+ buf[i] = 'A' + n%26;
+ n = n/26; // shift one digit
+ }
+
+ return buf+i+1;
+}
+
+
+
+void readsequence(FILE *file, uint32_t *count, uint32_t *length,
+ const HCFGrammar *g, const HCFSequence *seq) {
+ // tally up numbers of choices, and lengths of emitted strings.
+ // Immediately emit any nonterminals encountered.
+ HCFChoice** x = seq->items;
+
+ if (*x == NULL) {
+ return;
+ } else {
+ fprintf(file, "1");
+ HCharset cs;
+ unsigned int i, cscount=0;
+ for(; *x; x++) {
+ switch((*x)->type) {
+ case HCF_CHAR:
+ (*length)++;
+ break;
+ case HCF_END:
+ break;
+ case HCF_CHARSET:
+ cs = (*x)->charset;
+ for(i=0; i<256; i++) {
+ if (charset_isset(cs, i)) {
+ cscount++;
+ }
+ }
+ *count *= cscount;
+ break;
+ default: // HCF_CHOICE, non-terminal symbol
+ fprintf(file, "*%s(t)", nonterminal_name(g, *x));
+ break;
+ }
+ }
+ }
+}
+
+// For each nt in g->nts
+// For each choice in nt->key->seq
+// For all elements in sequence
+// Accumulate counts
+// Accumulate string lengths
+// Emit count*t^length
+void h_pprint_gfeqns(FILE *file, const HCFGrammar *g) {
+ if (g->nts->used < 1) {
+ return;
+ }
+
+ // determine maximum string length of symbol names
+ int len;
+ size_t s;
+ for(len=1, s=26; s < g->nts->used; len++, s*=26);
+
+ // iterate over g->nts
+ size_t i;
+ HHashTableEntry *hte;
+ for(i=0; i < g->nts->capacity; i++) {
+ for(hte = &g->nts->contents[i]; hte; hte = hte->next) {
+ if (hte->key == NULL) {
+ continue;
+ }
+
+ const HCFChoice *nt = hte->key;
+ fprintf(file, "%s(t) = ", nonterminal_name(g, nt));
+
+
+ for(HCFSequence **seq = nt->seq; *seq; seq++) {
+ if (seq != nt->seq) {
+ fprintf(file, " + ");
+ }
+ uint32_t count=1, length=0;
+ readsequence(file, &count, &length, g, *seq);
+ if(count == 1) {
+ if(length == 1) {
+ fprintf(file, "*t");
+ }
+ if(length > 1) {
+ fprintf(file, "*t^%d", length);
+ }
+ } else if(count > 1) {
+ if(length == 0) {
+ fprintf(file, "*%d", count);
+ }
+ if(length == 1) {
+ fprintf(file, "*%d*t", count);
+ }
+ if (length > 1) {
+ fprintf(file, "*%d*t^%d", count, length);
+ }
+ }
+ }
+
+ fprintf(file, "\n");
+ }
+ }
+}
+
+HParser* cfExample() {
+ HParser *n = h_ch('n');
+ HParser *E = h_indirect();
+ HParser *T = h_choice(h_sequence(h_ch('('), E, h_ch(')'), NULL), n, NULL);
+ HParser *E_ = h_choice(h_sequence(E, h_ch('-'), T, NULL), T, NULL);
+ h_bind_indirect(E, E_);
+ return E;
+}
+
+// The tie knot parsers below would work better if we could patch the gen.function
+// code above to allow user specification of non-default byte string "lengths",
+// so that U symbols don't contribute with factors of t to the gen. function.
+//
+// Alternatively: use multivariate generating functions to spit out different
+// variables for different terminals. This gets really messy with bigger alphabets.
+
+HParser* finkmao() {
+ HParser *L = h_ch('L');
+ HParser *R = h_ch('R');
+ HParser *C = h_ch('C');
+ HParser *U = h_ch('U');
+ HParser *Lnext = h_indirect();
+ HParser *Rnext = h_indirect();
+ HParser *Cnext = h_indirect();
+ HParser *L_ = h_choice(h_sequence(R, Rnext, NULL),
+ h_sequence(C, Cnext, NULL),
+ h_sequence(R, C, U, NULL), NULL);
+ HParser *R_ = h_choice(h_sequence(L, Lnext, NULL),
+ h_sequence(C, Cnext, NULL),
+ h_sequence(L, C, U, NULL), NULL);
+ HParser *C_ = h_choice(h_sequence(R, Rnext, NULL),
+ h_sequence(L, Lnext, NULL), NULL);
+ h_bind_indirect(Lnext, L_);
+ h_bind_indirect(Rnext, R_);
+ h_bind_indirect(Cnext, C_);
+ HParser *tie = h_choice(h_sequence(L, Lnext), NULL);
+ return tie;
+}
+
+HParser* finkmaoTW() {
+ HParser *T = h_ch('T');
+ HParser *W = h_ch('W');
+ HParser *U = h_ch('U');
+ HParser *prefix = h_choice(T, W, h_epsilon_p(), NULL);
+ HParser *pair = h_repeat_n(h_choice(T, W, NULL), 2);
+ HParser *tuck = h_choice(h_sequence(T, T, U, NULL),
+ h_sequence(W, W, U, NULL),
+ NULL);
+ return h_choice(h_sequence(prefix, h_many(pair), tuck, NULL));
+}
+
+HParser* depth1TW() {
+ HParser *T = h_ch('T');
+ HParser *W = h_ch('W');
+ HParser *U = h_ch('U');
+ HParser *prefix = h_choice(T, W, h_epsilon_p(), NULL);
+ HParser *pair = h_repeat_n(h_choice(T, W, NULL), 2);
+ HParser *tuck = h_choice(h_sequence(T, T, U, NULL),
+ h_sequence(W, W, U, NULL),
+ NULL);
+ return h_choice(h_sequence(prefix, h_many(h_choice(pair, tuck)), tuck, NULL));
+}
+
+HParser* depth1() {
+ HParser *L = h_ch('L');
+ HParser *R = h_ch('R');
+ HParser *C = h_ch('C');
+ HParser *U = h_ch('U');
+ HParser *lastR = h_indirect();
+ HParser *lastL = h_indirect();
+ HParser *lastC = h_indirect();
+ HParser *R_ = h_choice(h_sequence(L, R, lastR, NULL),
+ h_sequence(C, R, lastR, NULL),
+ h_sequence(L, C, lastC, NULL),
+ h_sequence(L, C, U, lastC, NULL),
+ h_sequence(L, C, U, NULL),
+ h_sequence(C, L, lastL, NULL),
+ h_sequence(C, L, U, lastL, NULL),
+ h_sequence(C, L, U, NULL),
+ NULL);
+ HParser *L_ = h_choice(h_sequence(R, L, lastR, NULL),
+ h_sequence(C, L, lastR, NULL),
+ h_sequence(R, C, lastC, NULL),
+ h_sequence(R, C, U, lastC, NULL),
+ h_sequence(R, C, U, NULL),
+ h_sequence(C, R, lastR, NULL),
+ h_sequence(C, R, U, lastR, NULL),
+ h_sequence(C, R, U, NULL),
+ NULL);
+ HParser *C_ = h_choice(h_sequence(L, C, lastR, NULL),
+ h_sequence(R, C, lastR, NULL),
+ h_sequence(L, R, lastR, NULL),
+ h_sequence(L, R, U, lastR, NULL),
+ h_sequence(L, R, U, NULL),
+ h_sequence(R, L, lastL, NULL),
+ h_sequence(R, L, U, lastL, NULL),
+ h_sequence(R, L, U, NULL),
+ NULL);
+ h_bind_indirect(lastR, R_);
+ h_bind_indirect(lastL, L_);
+ h_bind_indirect(lastC, C_);
+ return h_choice(h_sequence(L, lastL, NULL),
+ h_sequence(R, lastR, NULL),
+ h_sequence(C, lastC, NULL),
+ NULL);
+}
+
+HParser* depthNTW() {
+ HParser *T = h_ch('T');
+ HParser *W = h_ch('W');
+ HParser *U = h_ch('U');
+ HParser *prefix = h_choice(T, W, h_epsilon_p(), NULL);
+ HParser *pair = h_repeat_n(h_choice(T, W, NULL), 2);
+ HParser *tstart = h_indirect();
+ HParser *tw0 = h_indirect();
+ HParser *tw1 = h_indirect();
+ HParser *tw2 = h_indirect();
+ HParser *wstart = h_indirect();
+ HParser *wt0 = h_indirect();
+ HParser *wt1 = h_indirect();
+ HParser *wt2 = h_indirect();
+
+ HParser *T_ = h_choice(h_sequence(T, T, tw2, U, NULL),
+ h_sequence(T, W, tw0, U, NULL),
+ NULL);
+ HParser *tw0_ = h_choice(h_sequence(T, T, tw2, U, NULL),
+ h_sequence(T, W, tw0, U, NULL),
+ h_sequence(W, T, tw0, U, NULL),
+ h_sequence(W, W, tw1, U, NULL),
+ h_sequence(tstart, tw2, U, NULL),
+ h_sequence(wstart, tw1, U, NULL),
+ NULL);
+ HParser *tw1_ = h_choice(h_sequence(T, T, tw0, U, NULL),
+ h_sequence(T, W, tw1, U, NULL),
+ h_sequence(W, T, tw1, U, NULL),
+ h_sequence(W, W, tw2, U, NULL),
+ h_sequence(tstart, tw0, U, NULL),
+ h_sequence(wstart, tw2, U, NULL),
+ NULL);
+ HParser *tw2_ = h_choice(h_sequence(T, T, tw1, U, NULL),
+ h_sequence(T, W, tw2, U, NULL),
+ h_sequence(W, T, tw2, U, NULL),
+ h_sequence(W, W, tw0, U, NULL),
+ h_sequence(tstart, tw1, U, NULL),
+ h_sequence(wstart, tw0, U, NULL),
+ h_epsilon_p(),
+ NULL);
+
+ HParser *W_ = h_choice(h_sequence(W, W, wt2, U, NULL),
+ h_sequence(W, T, wt0, U, NULL),
+ NULL);
+ HParser *wt0_ = h_choice(h_sequence(W, W, wt2, U, NULL),
+ h_sequence(W, T, wt0, U, NULL),
+ h_sequence(T, W, wt0, U, NULL),
+ h_sequence(T, T, wt1, U, NULL),
+ h_sequence(wstart, wt2, U, NULL),
+ h_sequence(tstart, wt1, U, NULL),
+ NULL);
+ HParser *wt1_ = h_choice(h_sequence(W, W, wt0, U, NULL),
+ h_sequence(W, T, wt1, U, NULL),
+ h_sequence(T, W, wt1, U, NULL),
+ h_sequence(T, T, wt2, U, NULL),
+ h_sequence(wstart, wt0, U, NULL),
+ h_sequence(tstart, wt2, U, NULL),
+ NULL);
+ HParser *wt2_ = h_choice(h_sequence(W, W, wt1, U, NULL),
+ h_sequence(W, T, wt2, U, NULL),
+ h_sequence(T, W, wt2, U, NULL),
+ h_sequence(T, T, wt0, U, NULL),
+ h_sequence(wstart, wt1, U, NULL),
+ h_sequence(tstart, wt0, U, NULL),
+ h_epsilon_p(),
+ NULL);
+
+ h_bind_indirect(tstart, T_);
+ h_bind_indirect(tw0, tw0_);
+ h_bind_indirect(tw1, tw1_);
+ h_bind_indirect(tw2, tw2_);
+ h_bind_indirect(wstart, W_);
+ h_bind_indirect(wt0, wt0_);
+ h_bind_indirect(wt1, wt1_);
+ h_bind_indirect(wt2, wt2_);
+
+ HParser *tuck = h_choice(tstart, wstart, NULL);
+ return h_choice(h_sequence(prefix, h_many(h_choice(pair, tuck)), tuck, NULL));
+}
+
+
+int main(int argc, char **argv)
+{
+ HAllocator *mm__ = &system_allocator;
+
+
+ HCFGrammar *g = h_cfgrammar_(mm__, h_desugar_augmented(mm__, cfExample()));
+ if (g == NULL) {
+ fprintf(stderr, "h_cfgrammar failed\n");
+ return 1;
+ }
+ printf("\n==== Generating functions ====\n");
+ h_pprint_gfeqns(stdout, g);
+
+ printf("\n==== Grammar ====\n");
+ h_pprint_grammar(stdout, g, 0);
+}