github.com/consensys/gnark@v0.11.0/constraint/term.go (about)

     1  // Copyright 2020 ConsenSys AG
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package constraint
    16  
    17  import (
    18  	"math"
    19  )
    20  
    21  // ids of the coefficients with simple values in any cs.coeffs slice.
    22  const (
    23  	CoeffIdZero = iota
    24  	CoeffIdOne
    25  	CoeffIdTwo
    26  	CoeffIdMinusOne
    27  	CoeffIdMinusTwo
    28  )
    29  
    30  // Term represents a coeff * variable in a constraint system
    31  type Term struct {
    32  	CID, VID uint32
    33  }
    34  
    35  func (t *Term) MarkConstant() {
    36  	t.VID = math.MaxUint32
    37  }
    38  
    39  func (t *Term) IsConstant() bool {
    40  	return t.VID == math.MaxUint32
    41  }
    42  
    43  func (t *Term) WireID() int {
    44  	return int(t.VID)
    45  }
    46  
    47  func (t *Term) CoeffID() int {
    48  	return int(t.CID)
    49  }
    50  
    51  func (t Term) String(r Resolver) string {
    52  	sbb := NewStringBuilder(r)
    53  	sbb.WriteTerm(t)
    54  	return sbb.String()
    55  }
    56  
    57  // implements constraint.Compressible
    58  
    59  // Compress compresses the term into a slice of uint32 words.
    60  // For compatibility with test engine and LinearExpression, the term is encoded as:
    61  // 1, CID, VID (i.e a LinearExpression with a single term)
    62  func (t Term) Compress(to *[]uint32) {
    63  	(*to) = append((*to), 1, t.CID, t.VID)
    64  }