diff options
author | Tim King <taking@cs.nyu.edu> | 2012-12-14 20:09:54 -0500 |
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committer | Tim King <taking@cs.nyu.edu> | 2012-12-14 20:09:54 -0500 |
commit | edf971e2934367d160830a35e97a2e664e742b28 (patch) | |
tree | 07715a33a93a8edf2aec5afd71f71fb9b1c7d012 /src/util/integer_cln_imp.h | |
parent | 5d0d0b56d1383f1ad4027d8e6dc739c12cacced8 (diff) |
Changing the rewriter to use Boute's Euclidean definition of division.
Diffstat (limited to 'src/util/integer_cln_imp.h')
-rw-r--r-- | src/util/integer_cln_imp.h | 72 |
1 files changed, 68 insertions, 4 deletions
diff --git a/src/util/integer_cln_imp.h b/src/util/integer_cln_imp.h index 211c40741..b5452ae00 100644 --- a/src/util/integer_cln_imp.h +++ b/src/util/integer_cln_imp.h @@ -275,6 +275,61 @@ public: } /** + * Computes a quoitent and remainder according to Boute's Euclidean definition. + * euclidianDivideQuotient, euclidianDivideRemainder. + * + * Boute, Raymond T. (April 1992). + * The Euclidean definition of the functions div and mod. + * ACM Transactions on Programming Languages and Systems (TOPLAS) + * ACM Press. 14 (2): 127 - 144. doi:10.1145/128861.128862. + */ + static void euclidianQR(Integer& q, Integer& r, const Integer& x, const Integer& y) { + // compute the floor and then fix the value up if needed. + floorQR(q,r,x,y); + + if(r.strictlyNegative()){ + // if r < 0 + // abs(r) < abs(y) + // - abs(y) < r < 0, then 0 < r + abs(y) < abs(y) + // n = y * q + r + // n = y * q - abs(y) + r + abs(y) + if(r.sgn() >= 0){ + // y = abs(y) + // n = y * q - y + r + y + // n = y * (q-1) + (r+y) + q -= 1; + r += y; + }else{ + // y = -abs(y) + // n = y * q + y + r - y + // n = y * (q+1) + (r-y) + q += 1; + r -= y; + } + } + } + + /** + * Returns the quoitent according to Boute's Euclidean definition. + * See the documentation for euclidianQR. + */ + Integer euclidianDivideQuotient(const Integer& y) const { + Integer q,r; + euclidianQR(q,r, *this, y); + return q; + } + + /** + * Returns the remainfing according to Boute's Euclidean definition. + * See the documentation for euclidianQR. + */ + Integer euclidianDivideRemainder(const Integer& y) const { + Integer q,r; + euclidianQR(q,r, *this, y); + return r; + } + + /** * If y divides *this, then exactQuotient returns (this/y) */ Integer exactQuotient(const Integer& y) const { @@ -371,15 +426,24 @@ public: return cln::cl_I_to_int(sgn); } - bool isZero() const { - return cln::zerop(d_value); + + inline bool strictlyPositive() const { + return sgn() > 0; + } + + inline bool strictlyNegative() const { + return sgn() < 0; + } + + inline bool isZero() const { + return sgn() == 0; } - bool isOne() const { + inline bool isOne() const { return d_value == 1; } - bool isNegativeOne() const { + inline bool isNegativeOne() const { return d_value == -1; } |