14 files changed, 830 insertions, 18 deletions

diff --git a/src/cube.c b/experiments/cube.c
index 4372b5e..4372b5e 100644
--- a/src/cube.c
+++ b/experiments/cube.c
diff --git a/experiments/cube.h b/experiments/cube.h
new file mode 100644
index 0000000..b916f96
--- /dev/null
+++ b/experiments/cube.h
@@ -0,0 +1,27 @@
+typedef enum {
+        U, U2, U3, D, D2, D3,
+        R, R2, R3, L, L2, L3,
+        F, F2, F3, B, B2, B3
+} move_t;
+typedef struct {
+        uint64_t e;
+        uint64_t c;
+} cube_t;
+
+extern cube_t solvedcube;
+extern cube_t errorcube;
+
+bool isconsistent(cube_t);
+bool issolved(cube_t);
+
+cube_t readcube(char *);
+void writecube(cube_t, char *);
+
+int readmoves(char *, move_t *);
+void writemoves(move_t *, int, char *);
+
+cube_t move(cube_t, move_t);
+
+/*
+cube_t inverse(cube_t);
+*/
diff --git a/src/array_cube.c b/src/array_cube.c
new file mode 100644
index 0000000..3445658
--- /dev/null
+++ b/src/array_cube.c
@@ -0,0 +1,712 @@
+/*
+In this implementation of the cube.h interface, the cube is represented
+by two arrays of 8-bit unsigned integers, one for centers and one for
+corners.  The 4 leas-significant digits of each bit determine the piece,
+the other 4 are used for orientation or kept to 0.
+
+Edges:
+        xxxopppp (x = unused, o = orientation, p = piece)
+
+Corners:
+        xooxpppp (x = unused, o = orientation, p = piece)
+
+The two bits for CO are shifted to make it possible to perform mod 3
+operations (sum, inverse) using only addition and bitwise operators.
+See below for details.
+
+The third bit is needed because x+y+1 can exceed 4.
+*/
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <string.h>
+
+#ifdef DEBUG
+#include <stdio.h>
+#endif
+
+#include "cube.h"
+
+#define _c_ufr      0U
+#define _c_ubl      1U
+#define _c_dfl      2U
+#define _c_dbr      3U
+#define _c_ufl      4U
+#define _c_ubr      5U
+#define _c_dfr      6U
+#define _c_dbl      7U
+
+#define _e_uf       0U
+#define _e_ub       1U
+#define _e_db       2U
+#define _e_df       3U
+#define _e_ur       4U
+#define _e_ul       5U
+#define _e_dl       6U
+#define _e_dr       7U
+#define _e_fr       8U
+#define _e_fl       9U
+#define _e_bl       10U
+#define _e_br       11U
+
+#define _eoshift    4U
+#define _coshift    5U
+
+#define _pbits      0xFU
+#define _eobit      0x10U
+#define _cobits     0xF0U
+#define _cobits2    0x60U
+#define _ctwist_cw  0x20U
+#define _ctwist_ccw 0x40U
+#define _eflip      0x10U
+#define _error      0xFFU
+
+static char *cornerstr[] = {
+        [_c_ufr] = "UFR",
+        [_c_ubl] = "UBL",
+        [_c_dfl] = "DFL",
+        [_c_dbr] = "DBR",
+        [_c_ufl] = "UFL",
+        [_c_ubr] = "UBR",
+        [_c_dfr] = "DFR",
+        [_c_dbl] = "DBL"
+};
+
+static char *cornerstralt[] = {
+        [_c_ufr] = "URF",
+        [_c_ubl] = "ULB",
+        [_c_dfl] = "DLF",
+        [_c_dbr] = "DRB",
+        [_c_ufl] = "ULF",
+        [_c_ubr] = "URB",
+        [_c_dfr] = "DRF",
+        [_c_dbl] = "DLB"
+};
+
+static char *edgestr[] = {
+        [_e_uf] = "UF",
+        [_e_ub] = "UB",
+        [_e_db] = "DB",
+        [_e_df] = "DF",
+        [_e_ur] = "UR",
+        [_e_ul] = "UL",
+        [_e_dl] = "DL",
+        [_e_dr] = "DR",
+        [_e_fr] = "FR",
+        [_e_fl] = "FL",
+        [_e_bl] = "BL",
+        [_e_br] = "BR"
+};
+
+static char *movestr[] = {
+        [U]  = "U",
+        [U2] = "U2",
+        [U3] = "U'",
+        [D]  = "D",
+        [D2] = "D2",
+        [D3] = "D'",
+        [R]  = "R",
+        [R2] = "R2",
+        [R3] = "R'",
+        [L]  = "L",
+        [L2] = "L2",
+        [L3] = "L'",
+        [F]  = "F",
+        [F2] = "F2",
+        [F3] = "F'",
+        [B]  = "B",
+        [B2] = "B2",
+        [B3] = "B'",
+};
+
+cube_t solvedcube = {
+        .c = {
+                [_c_ufr] = _c_ufr,
+                [_c_ubl] = _c_ubl,
+                [_c_dfl] = _c_dfl,
+                [_c_dbr] = _c_dbr,
+                [_c_ufl] = _c_ufl,
+                [_c_ubr] = _c_ubr,
+                [_c_dfr] = _c_dfr,
+                [_c_dbl] = _c_dbl
+        },
+        .e = {
+                [_e_uf] = _e_uf,
+                [_e_ub] = _e_ub,
+                [_e_db] = _e_db,
+                [_e_df] = _e_df,
+                [_e_ur] = _e_ur,
+                [_e_ul] = _e_ul,
+                [_e_dl] = _e_dl,
+                [_e_dr] = _e_dr,
+                [_e_fr] = _e_fr,
+                [_e_fl] = _e_fl,
+                [_e_bl] = _e_bl,
+                [_e_br] = _e_br
+        }
+};
+
+static cube_t errorcube = { .e = {0}, .c = {0} };
+
+static uint8_t readco(char *);
+static uint8_t readcp(char *);
+static uint8_t readeo(char *);
+static uint8_t readep(char *);
+static uint8_t readmove(char);
+static uint8_t readmodifier(char);
+static int permsign(uint8_t *, int);
+static cube_t compose(cube_t, cube_t);
+
+static uint8_t
+readco(char *str)
+{
+        if (*str == '0')
+                return 0;
+        if (*str == '1')
+                return _ctwist_cw;
+        if (*str == '2')
+                return _ctwist_ccw;
+
+#ifdef DEBUG
+        fprintf(stderr, "Error reading CO\n");
+#endif
+        return _error;
+}
+
+static uint8_t
+readcp(char *str)
+{
+        uint8_t c;
+
+        for (c = 0; c < 8; c++)
+                if (!strncmp(str, cornerstr[c], 3) ||
+                    !strncmp(str, cornerstralt[c], 3))
+                        return c;
+
+#ifdef DEBUG
+        fprintf(stderr, "Error reading CP\n");
+#endif
+        return _error;
+}
+
+static uint8_t
+readeo(char *str)
+{
+        if (*str == '0')
+                return 0;
+        if (*str == '1')
+                return _eflip;
+
+#ifdef DEBUG
+        fprintf(stderr, "Error reading EO\n");
+#endif
+        return _error;
+}
+
+static uint8_t
+readep(char *str)
+{
+        uint8_t e;
+
+        for (e = 0; e < 12; e++)
+                if (!strncmp(str, edgestr[e], 2))
+                        return e;
+
+#ifdef DEBUG
+        fprintf(stderr, "Error reading EP\n");
+#endif
+        return _error;
+}
+
+cube_t
+readcube(char *buf)
+{
+        int i;
+        uint8_t piece, orient;
+        cube_t ret = {0};
+        char *b = buf;
+
+        for (i = 0; i < 12; i++) {
+                while (*b == ' ' || *b == '\t' || *b == '\n')
+                        b++;
+                if ((piece = readep(b)) == _error)
+                        goto readcube_error;
+                b += 2;
+                if ((orient = readeo(b)) == _error)
+                        goto readcube_error;
+                b++;
+                ret.e[i] = piece | orient;
+        }
+        for (i = 0; i < 8; i++) {
+                while (*b == ' ' || *b == '\t' || *b == '\n')
+                        b++;
+                if ((piece = readcp(b)) == _error)
+                        goto readcube_error;
+                b += 3;
+                if ((orient = readco(b)) == _error)
+                        goto readcube_error;
+                b++;
+                ret.c[i] = piece | orient;
+        }
+
+        return ret;
+
+readcube_error:
+#ifdef DEBUG
+        fprintf(stderr, "readcube error\n");
+#endif
+        return errorcube;
+}
+
+void
+writecube(cube_t cube, char *buf)
+{
+        char *errormsg;
+        uint8_t piece, orient;
+        size_t len;
+        int i;
+
+        if (!isconsistent(cube)) {
+                errormsg = "ERROR: cannot write inconsistent cube";
+                goto writecube_error;
+        }
+
+        for (i = 0; i < 12; i++) {
+                piece = cube.e[i] & _pbits;
+                orient = (cube.e[i] & _eobit) >> _eoshift;
+                buf[4*i    ] = edgestr[piece][0];
+                buf[4*i + 1] = edgestr[piece][1];
+                buf[4*i + 2] = orient + '0';
+                buf[4*i + 3] = ' ';
+        }
+        for (i = 0; i < 8; i++) {
+                piece = cube.c[i] & _pbits;
+                orient = (cube.c[i] & _cobits) >> _coshift;
+                buf[48 + 5*i    ] = cornerstr[piece][0];
+                buf[48 + 5*i + 1] = cornerstr[piece][1];
+                buf[48 + 5*i + 2] = cornerstr[piece][2];
+                buf[48 + 5*i + 3] = orient + '0';
+                buf[48 + 5*i + 4] = ' ';
+        }
+
+        buf[48+39] = '\0';
+
+        return;
+
+writecube_error:
+#ifdef DEBUG
+        fprintf(stderr, "writecube error, see stdout for details\n");
+#endif
+        len = strlen(errormsg);
+        memcpy(buf, errormsg, len);
+        buf[len] = '\n';
+        buf[len+1] = '\0';
+}
+
+
+static uint8_t
+readmove(char c)
+{
+        switch (c) {
+        case 'U':
+                return U;
+        case 'D':
+                return D;
+        case 'R':
+                return R;
+        case 'L':
+                return L;
+        case 'F':
+                return F;
+        case 'B':
+                return B;
+        default:
+                return _error;
+        }
+}
+
+static uint8_t
+readmodifier(char c)
+{
+        switch (c) {
+        case '1': /* Fallthrough */
+        case '2': /* Fallthrough */
+        case '3':
+                return c - '0' - 1;
+        case '\'':
+                return 2;
+        default:
+                return 0;
+        }
+}
+
+int
+readmoves(char *buf, move_t *m)
+{
+        int n;
+        uint64_t r;
+        char *b;
+
+        for (b = buf, n = 0; *b != '\0'; b++) {
+                while (*b == ' ' || *b == '\t' || *b == '\n')
+                        b++;
+                if (*b == '\0')
+                        return n;
+                if ((r = readmove(*b)) == _error)
+                        goto readmoves_error;
+                m[n] = (move_t)r;
+                if ((r = readmodifier(*(b+1))) != 0) {
+                        b++;
+                        m[n] += r;
+                }
+                n++;
+        }
+
+        return n;
+
+readmoves_error:
+#ifdef DEBUG
+        fprintf(stderr, "readmoves error\n");
+#endif
+        return -1;
+}
+
+void
+writemoves(move_t *m, int n, char *buf)
+{
+        int i;
+        size_t len;
+        char *b, *s;
+
+        for (i = 0, b = buf; i < n; i++, b++) {
+                s = movestr[m[i]];
+                len = strlen(s);
+                memcpy(b, s, len);
+                b += len;       
+                *b = ' ';
+        }
+        *b = '\0';
+}
+
+
+static int
+permsign(uint8_t *a, int n)
+{
+        int i, j;
+        uint8_t ret = 0;
+
+        for (i = 0; i < n; i++)
+                for (j = i+1; j < n; j++)
+                        ret += (a[i] & _pbits) > (a[j] & _pbits) ? 1 : 0;
+
+        return ret % 2;
+}
+
+bool
+isconsistent(cube_t cube)
+{
+        int8_t p, psum, eosum, co, cosum;
+        bool found[12];
+        int i;
+
+        psum = 0;
+        for (i = 0; i < 12; i++)
+                found[i] = false;
+        for (i = 0; i < 12; i++) {
+                p = cube.e[i] & _pbits;
+                if (p >= 12)
+                        goto inconsistent_ep;
+                found[p] = true;
+        }
+        for (i = 0; i < 12; i++)
+                if (!found[i])
+                        goto inconsistent_ep;
+        psum = permsign(cube.e, 12);
+
+        for (i = 0; i < 8; i++)
+                found[i] = false;
+        for (i = 0; i < 8; i++) {
+                p = cube.c[i] & _pbits;
+                if (p >= 8)
+                        goto inconsistent_cp;
+                found[p] = true;
+        }
+        for (i = 0; i < 8; i++)
+                if (!found[i])
+                        goto inconsistent_cp;
+        psum += permsign(cube.c, 8);
+
+        if (psum % 2 != 0)
+                goto inconsistent_parity;
+
+        eosum = 0;
+        for (i = 0; i < 12; i++)
+                eosum += (cube.e[i] & _eobit) >> _eoshift;
+        if (eosum % 2 != 0)
+                goto inconsistent_eo;
+
+        cosum = 0;
+        for (i = 0; i < 8; i++) {
+                co = (cube.c[i] & _cobits) >> _coshift;
+                if (co > 2)
+                        goto inconsistent_co;
+                cosum += co;
+        }
+        if (cosum % 3 != 0)
+                goto inconsistent_co;
+
+        return true;
+
+inconsistent_ep:
+#ifdef DEBUG
+        fprintf(stderr, "Inconsistent EP\n");
+#endif
+        goto inconsistent_return;
+inconsistent_cp:
+#ifdef DEBUG
+        fprintf(stderr, "Inconsistent CP\n");
+#endif
+        goto inconsistent_return;
+inconsistent_parity:
+#ifdef DEBUG
+        fprintf(stderr, "Inconsistent parity\n");
+#endif
+        goto inconsistent_return;
+inconsistent_eo:
+#ifdef DEBUG
+        fprintf(stderr, "Inconsistent EO\n");
+#endif
+        goto inconsistent_return;
+inconsistent_co:
+#ifdef DEBUG
+        fprintf(stderr, "Inconsistent CO\n");
+#endif
+        goto inconsistent_return;
+inconsistent_return:
+        return false;
+}
+
+bool
+equal(cube_t cube1, cube_t cube2)
+{
+        uint8_t i;
+
+        for (i = 0; i < 12; i++)
+                if (cube1.e[i] != cube2.e[i])
+                        return false;
+
+        for (i = 0; i < 8; i++)
+                if (cube1.c[i] != cube2.c[i])
+                        return false;
+
+        return true;
+}
+
+bool
+issolved(cube_t cube)
+{
+        return equal(cube, solvedcube);
+}
+
+bool
+iserror(cube_t cube)
+{
+        return equal(cube, errorcube);
+}
+
+cube_t
+move(cube_t c, move_t m)
+{
+        cube_t ret;
+        uint8_t aux, auy, auz;
+
+#ifdef DEBUG
+        if (!isconsistent(c))
+                goto move_inconsistent;
+#endif
+
+#define PERM4(r, i, j, k, l) \
+    aux = r[i];              \
+    r[i] = r[l];             \
+    r[l] = r[k];             \
+    r[k] = r[j];             \
+    r[j] = aux;
+#define PERM22(r, i, j, k, l) \
+    aux = r[i];               \
+    r[i] = r[j];              \
+    r[j] = aux;               \
+    aux = r[k];               \
+    r[k] = r[l];              \
+    r[l] = aux;
+#define CO(a, b)                         \
+    aux = (a & _cobits) + (b & _cobits); \
+    auy = (aux + _ctwist_cw) >> 2U;      \
+    auz = (aux + auy) & _cobits2;        \
+    a = (a & _pbits) | auz;
+#define CO4(r, i, j, k, l) \
+    CO(r[i], _ctwist_cw)   \
+    CO(r[j], _ctwist_cw)   \
+    CO(r[k], _ctwist_ccw)  \
+    CO(r[l], _ctwist_ccw)
+#define EO4(r, i, j, k, l) \
+    r[i] ^= _eobit;        \
+    r[j] ^= _eobit;        \
+    r[k] ^= _eobit;        \
+    r[l] ^= _eobit;
+
+        ret = c;
+
+        switch (m) {
+        case U:
+                PERM4(ret.e, _e_uf, _e_ul, _e_ub, _e_ur)
+                PERM4(ret.c, _c_ufr, _c_ufl, _c_ubl, _c_ubr)
+
+                return ret;
+        case U2:
+                PERM22(ret.e, _e_uf, _e_ub, _e_ul, _e_ur)
+                PERM22(ret.c, _c_ufr, _c_ubl, _c_ufl, _c_ubr)
+
+                return ret;
+        case U3:
+                PERM4(ret.e, _e_uf, _e_ur, _e_ub, _e_ul)
+                PERM4(ret.c, _c_ufr, _c_ubr, _c_ubl, _c_ufl)
+
+                return ret;
+        case D:
+                PERM4(ret.e, _e_df, _e_dr, _e_db, _e_dl)
+                PERM4(ret.c, _c_dfr, _c_dbr, _c_dbl, _c_dfl)
+
+                return ret;
+        case D2:
+                PERM22(ret.e, _e_df, _e_db, _e_dr, _e_dl)
+                PERM22(ret.c, _c_dfr, _c_dbl, _c_dbr, _c_dfl)
+
+                return ret;
+        case D3:
+                PERM4(ret.e, _e_df, _e_dl, _e_db, _e_dr)
+                PERM4(ret.c, _c_dfr, _c_dfl, _c_dbl, _c_dbr)
+
+                return ret;
+        case R:
+                PERM4(ret.e, _e_ur, _e_br, _e_dr, _e_fr)
+                PERM4(ret.c, _c_ufr, _c_ubr, _c_dbr, _c_dfr)
+
+                CO4(ret.c, _c_ubr, _c_dfr, _c_ufr, _c_dbr)
+
+                return ret;
+        case R2:
+                PERM22(ret.e, _e_ur, _e_dr, _e_fr, _e_br)
+                PERM22(ret.c, _c_ufr, _c_dbr, _c_ubr, _c_dfr)
+
+                return ret;
+        case R3:
+                PERM4(ret.e, _e_ur, _e_fr, _e_dr, _e_br)
+                PERM4(ret.c, _c_ufr, _c_dfr, _c_dbr, _c_ubr)
+
+                CO4(ret.c, _c_ubr, _c_dfr, _c_ufr, _c_dbr)
+
+                return ret;
+        case L:
+                PERM4(ret.e, _e_ul, _e_fl, _e_dl, _e_bl)
+                PERM4(ret.c, _c_ufl, _c_dfl, _c_dbl, _c_ubl)
+
+                CO4(ret.c, _c_ufl, _c_dbl, _c_dfl, _c_ubl)
+
+                return ret;
+        case L2:
+                PERM22(ret.e, _e_ul, _e_dl, _e_fl, _e_bl)
+                PERM22(ret.c, _c_ufl, _c_dbl, _c_ubl, _c_dfl)
+
+                return ret;
+        case L3:
+                PERM4(ret.e, _e_ul, _e_bl, _e_dl, _e_fl)
+                PERM4(ret.c, _c_ufl, _c_ubl, _c_dbl, _c_dfl)
+
+                CO4(ret.c, _c_ufl, _c_dbl, _c_dfl, _c_ubl)
+
+                return ret;
+        case F:
+                PERM4(ret.e, _e_uf, _e_fr, _e_df, _e_fl)
+                PERM4(ret.c, _c_ufr, _c_dfr, _c_dfl, _c_ufl)
+
+                EO4(ret.e, _e_uf, _e_fr, _e_df, _e_fl)
+                CO4(ret.c, _c_ufr, _c_dfl, _c_dfr, _c_ufl)
+
+                return ret;
+        case F2:
+                PERM22(ret.e, _e_uf, _e_df, _e_fr, _e_fl)
+                PERM22(ret.c, _c_ufr, _c_dfl, _c_ufl, _c_dfr)
+
+                return ret;
+        case F3:
+                PERM4(ret.e, _e_uf, _e_fl, _e_df, _e_fr)
+                PERM4(ret.c, _c_ufr, _c_ufl, _c_dfl, _c_dfr)
+
+                EO4(ret.e, _e_uf, _e_fr, _e_df, _e_fl)
+                CO4(ret.c, _c_ufr, _c_dfl, _c_dfr, _c_ufl)
+
+                return ret;
+        case B:
+                PERM4(ret.e, _e_ub, _e_bl, _e_db, _e_br)
+                PERM4(ret.c, _c_ubr, _c_ubl, _c_dbl, _c_dbr)
+
+                EO4(ret.e, _e_ub, _e_br, _e_db, _e_bl)
+                CO4(ret.c, _c_ubl, _c_dbr, _c_dbl, _c_ubr)
+
+                return ret;
+        case B2:
+                PERM22(ret.e, _e_ub, _e_db, _e_br, _e_bl)
+                PERM22(ret.c, _c_ubr, _c_dbl, _c_ubl, _c_dbr)
+
+                return ret;
+        case B3:
+                PERM4(ret.e, _e_ub, _e_br, _e_db, _e_bl)
+                PERM4(ret.c, _c_ubr, _c_dbr, _c_dbl, _c_ubl)
+
+                EO4(ret.e, _e_ub, _e_br, _e_db, _e_bl)
+                CO4(ret.c, _c_ubl, _c_dbr, _c_dbl, _c_ubr)
+
+                return ret;
+        default:
+                goto move_unknown;
+        }
+
+move_inconsistent:
+        fprintf(stderr, "move error, inconsistent cube\n");
+        goto move_error;
+move_unknown:
+        fprintf(stderr, "mover error, unknown move\n");
+        goto move_error;
+move_error:
+        return errorcube;
+}
+
+cube_t
+inverse(cube_t c)
+{
+        uint8_t i, piece, orien;
+        cube_t ret = {0};
+
+#ifdef DEBUG
+        if (!isconsistent(c))
+                goto inverse_inconsistent;
+#endif
+
+        for (i = 0; i < 12; i++) {
+                piece = c.e[i & _pbits];
+                orien = piece & _eobit;
+                ret.e[piece & _pbits] = i | orien;
+        }
+
+        for (i = 0; i < 8; i++) {
+                piece = c.c[i & _pbits];
+                orien = ((piece << 1) | (piece >> 1)) & _cobits2;
+                ret.c[piece & _pbits] = i | orien;
+        }
+
+        return ret;
+
+inverse_inconsistent:
+        fprintf(stderr, "inverse error, inconsistent cube\n");
+        return errorcube;
+}
diff --git a/src/cube.h b/src/cube.h
index b916f96..836bb5d 100644
--- a/src/cube.h
+++ b/src/cube.h
@@ -3,25 +3,51 @@ typedef enum {
         R, R2, R3, L, L2, L3,
         F, F2, F3, B, B2, B3
 } move_t;
+
 typedef struct {
-        uint64_t e;
-        uint64_t c;
+        uint8_t c[8];
+        uint8_t e[12];
 } cube_t;
 
 extern cube_t solvedcube;
-extern cube_t errorcube;
 
-bool isconsistent(cube_t);
-bool issolved(cube_t);
+/*
+The functions readcube() and writecube() use the following format.
+
+Each edge is represented by two letters denoting the sides it belongs to
+and one number denoting its orientation (0 oriented, 1 mis-oriented).
+Similarly, each corner is represented by three letters and a number
+(0 oriented, 1 twisted clockwise, 2 twisted counter-clockwise).
+Edge orientation is relative to the F / B axis, corner orientation is
+relative to the U / D axis.
+
+The pieces are ordered such that the solved cube looks like this:
+
+UF0 UB0 DB0 DF0 UR0 UL0 DL0 DR0 FR0 FL0 BL0 BR0
+UFR0 UBL0 DFL0 DBR0 UFL0 UBR0 DFR0 DBL0
+
+Whitespace (including newlines) between pieces is ignored when reading
+the cube, and a single whitespace character is added between pieces
+when writing.
+
+The cube after the moves R'U'F looks like this:
+
+FL1 BR0 DB0 UR1 UF0 UB0 DL0 FR0 UL1 DF1 BL0 DR0
+UBL1 DBR1 UFR2 DFR2 DFL2 UBL2 UFL2 DBL0
+
+More formats might be supported in the future.
+*/
 
 cube_t readcube(char *);
 void writecube(cube_t, char *);
 
+bool isconsistent(cube_t);
+bool equal(cube_t, cube_t);
+bool issolved(cube_t);
+bool iserror(cube_t);
+
 int readmoves(char *, move_t *);
 void writemoves(move_t *, int, char *);
 
 cube_t move(cube_t, move_t);
-
-/*
 cube_t inverse(cube_t);
-*/
diff --git a/test/00_basic/all.out b/test/00_basic/all.out
index d77f7f4..aad167e 100644
--- a/test/00_basic/all.out
+++ b/test/00_basic/all.out
@@ -2,3 +2,6 @@ Solved is consistent
 Solved is solved
 Zero is NOT consistent
 Zero is NOT solved
+Solved and Solved are equal
+Solved and Zero are NOT equal
+Zero and Solved are NOT equal
diff --git a/test/00_basic/basic_tests.c b/test/00_basic/basic_tests.c
index cc2a55c..8c52941 100644
--- a/test/00_basic/basic_tests.c
+++ b/test/00_basic/basic_tests.c
@@ -4,16 +4,29 @@
 
 #include "../../src/cube.h"
 
+void
+check(cube_t cube, char *name)
+{
+        printf("%s is%s consistent\n", name, isconsistent(cube) ? "" : " NOT");
+        printf("%s is%s solved\n", name, issolved(cube) ? "" : " NOT");
+}
+
+void
+check2(cube_t cube1, char *name1, cube_t cube2, char *name2)
+{
+        printf("%s and %s are%s equal\n", name1, name2,
+            equal(cube1, cube2) ? "" : " NOT");
+}
+
 int main() {
-        cube_t z, s;
+        cube_t zero = (cube_t){0};
 
-        s = solvedcube;
-        printf("Solved %s consistent\n", isconsistent(s) ? "is" : "is NOT");
-        printf("Solved %s solved\n", issolved(s) ? "is" : "is NOT");
+        check(solvedcube, "Solved");
+        check(zero, "Zero");
 
-        z = (cube_t){0};
-        printf("Zero %s consistent\n", isconsistent(z) ? "is" : "is NOT");
-        printf("Zero %s solved\n", issolved(z) ? "is" : "is NOT");
+        check2(solvedcube, "Solved", solvedcube, "Solved");
+        check2(solvedcube, "Solved", zero, "Zero");
+        check2(zero, "Zero", solvedcube, "Solved");
 
         return 0;
 }
diff --git a/test/01_io/io_tests.c b/test/01_io/io_tests.c
index 1ef99d0..42ef9b8 100644
--- a/test/01_io/io_tests.c
+++ b/test/01_io/io_tests.c
@@ -15,7 +15,7 @@ int main() {
 
         cube = readcube(str);
 
-        if (cube.e == errorcube.e && cube.c == errorcube.c) {
+        if (iserror(cube)) {
                 printf("Error reading cube\n");
         } else if (!isconsistent(cube)) {
                 printf("Cube is inconsistent\n");
diff --git a/test/02_move/move_tests.c b/test/02_move/move_tests.c
index 23fc45e..ac25de3 100644
--- a/test/02_move/move_tests.c
+++ b/test/02_move/move_tests.c
@@ -27,7 +27,7 @@ int main() {
         for (i = 0; i < n; i++)
                 cube = move(cube, moves[i]);
 
-        if (cube.e == errorcube.e && cube.c == errorcube.c) {
+        if (iserror(cube)) {
                 printf("Error moving cube\n");
         } else if (!isconsistent(cube)) {
                 printf("Moved cube is inconsistent\n");
diff --git a/test/03_inverse/00_solved.in b/test/03_inverse/00_solved.in
new file mode 100644
index 0000000..dff224d
--- /dev/null
+++ b/test/03_inverse/00_solved.in
@@ -0,0 +1 @@
+UF0 UB0 DB0 DF0 UR0 UL0 DL0 DR0 FR0 FL0 BL0 BR0 UFR0 UBL0 DFL0 DBR0 UFL0 UBR0 DFR0 DBL0
diff --git a/test/03_inverse/00_solved.out b/test/03_inverse/00_solved.out
new file mode 100644
index 0000000..dff224d
--- /dev/null
+++ b/test/03_inverse/00_solved.out
@@ -0,0 +1 @@
+UF0 UB0 DB0 DF0 UR0 UL0 DL0 DR0 FR0 FL0 BL0 BR0 UFR0 UBL0 DFL0 DBR0 UFL0 UBR0 DFR0 DBL0
diff --git a/test/03_inverse/01_scrambled.in b/test/03_inverse/01_scrambled.in
new file mode 100644
index 0000000..263213b
--- /dev/null
+++ b/test/03_inverse/01_scrambled.in
@@ -0,0 +1 @@
+DR0 DB0 BL0 DF1 UB0 UR1 FR1 UF0 FL1 DL0 BR1 UL1 DBL2 DFL0 UBR1 DFR2 UFR0 DBR1 UBL0 UFL0
diff --git a/test/03_inverse/01_scrambled.out b/test/03_inverse/01_scrambled.out
new file mode 100644
index 0000000..25089c6
--- /dev/null
+++ b/test/03_inverse/01_scrambled.out
@@ -0,0 +1 @@
+DR0 UR0 UB0 DF1 UL1 BR1 FL0 UF0 DL1 FR1 DB0 BL1 UFL0 DFR0 UBL0 UBR2 DBL0 DFL2 DBR1 UFR1
diff --git a/test/03_inverse/inverse_tests.c b/test/03_inverse/inverse_tests.c
new file mode 100644
index 0000000..5fab71a
--- /dev/null
+++ b/test/03_inverse/inverse_tests.c
@@ -0,0 +1,27 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "../../src/cube.h"
+
+#define STRLENMAX 10000
+
+int main() {
+        char str[STRLENMAX];
+        cube_t cube, inv;
+
+        fgets(str, STRLENMAX, stdin);
+        cube = readcube(str);
+        inv = inverse(cube);
+
+        if (iserror(inv)) {
+                printf("Error inverting cube\n");
+        } else if (!isconsistent(inv)) {
+                printf("Inverted cube is inconsistent\n");
+        } else {
+                writecube(inv, str);
+                printf("%s\n", str);
+        }
+
+        return 0;
+}
diff --git a/test/test.sh b/test/test.sh
index d59270b..75be809 100755
--- a/test/test.sh
+++ b/test/test.sh
@@ -5,7 +5,7 @@ CC="cc -DDEBUG -std=c99 -pthread -pedantic -Wall -Wextra \
 if [ $(uname) != "OpenBSD" ]; then
         CC="$CC -fsanitize=address -fsanitize=undefined"
 fi
-SRC="src/cube.c"
+SRC="src/array_cube.c"
 TESTBIN="test/run"
 TESTOUT="test/last.out"
 TESTERR="test/last.err"