Merge other basic circuits here

circuits/multiplexer.circom

@@ -0,0 +1,93 @@
+/*
+    Copyright 2018 0KIMS association.
+
+    This file is part of circom (Zero Knowledge Circuit Compiler).
+
+    circom is a free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    circom is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
+    License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with circom. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+// --> Assignation without constraint
+// <-- Assignation without constraint
+// === Constraint
+// <== Assignation with constraint
+// ==> Assignation with constraint
+// All variables are members of the field F[p]
+// https://github.com/zcash-hackworks/sapling-crypto
+// https://github.com/ebfull/bellman
+
+/*
+function log2(a) {
+    if (a==0) {
+        return 0;
+    }
+    let n = 1;
+    let r = 1;
+    while (n<a) {
+        r++;
+        n *= 2;
+    }
+    return r;
+}
+*/
+
+template EscalarProduct(w) {
+    signal input in1[w];
+    signal input in2[w];
+    signal output out;
+    signal aux[w];
+    var lc = 0;
+    for (var i=0; i<w; i++) {
+        aux[i] <== in1[i]*in2[i];
+        lc = lc + aux[i];
+    }
+    out <== lc;
+}
+
+template Decoder(w) {
+    signal input inp;
+    signal output out[w];
+    signal output success;
+    var lc=0;
+
+    for (var i=0; i<w; i++) {
+        out[i] <-- (inp == i) ? 1 : 0;
+        out[i] * (inp-i) === 0;
+        lc = lc + out[i];
+    }
+
+    lc ==> success;
+    success * (success -1) === 0;
+}
+
+
+template Multiplexor(wIn, nIn) {
+    signal input inp[nIn][wIn];
+    signal input sel;
+    signal output out[wIn];
+    component Decoder(nIn) dec;
+    component EscalarProduct(nIn) ep[wIn];
+    sel ==> dec.inp;
+    for (var j=0; j<wIn; j++) {
+        for (var k=0; k<nIn; k++) {
+            inp[k][j] ==> ep[j].in1[k];
+            dec.out[k] ==> ep[j].in2[k];
+        }
+        ep[j].out ==> out[j];
+    }
+    dec.success === 1;
+}
+
+component Multiplexor(8,3) main;
+
+