solvespace/expr.cpp

//-----------------------------------------------------------------------------
// The symbolic algebra system used to write our constraint equations;
// routines to build expressions in software or from a user-provided string,
// and to compute the partial derivatives that we'll use when write our
// Jacobian matrix.
//
// Copyright 2008-2013 Jonathan Westhues.
//-----------------------------------------------------------------------------
#include "solvespace.h"

ExprVector ExprVector::From(Expr *x, Expr *y, Expr *z) {
    ExprVector r = { x, y, z};
    return r;
}

ExprVector ExprVector::From(Vector vn) {
    ExprVector ve;
    ve.x = Expr::From(vn.x);
    ve.y = Expr::From(vn.y);
    ve.z = Expr::From(vn.z);
    return ve;
}

ExprVector ExprVector::From(hParam x, hParam y, hParam z) {
    ExprVector ve;
    ve.x = Expr::From(x);
    ve.y = Expr::From(y);
    ve.z = Expr::From(z);
    return ve;
}

ExprVector ExprVector::From(double x, double y, double z) {
    ExprVector ve;
    ve.x = Expr::From(x);
    ve.y = Expr::From(y);
    ve.z = Expr::From(z);
    return ve;
}

ExprVector ExprVector::Minus(ExprVector b) {
    ExprVector r;
    r.x = x->Minus(b.x);
    r.y = y->Minus(b.y);
    r.z = z->Minus(b.z);
    return r;
}

ExprVector ExprVector::Plus(ExprVector b) {
    ExprVector r;
    r.x = x->Plus(b.x);
    r.y = y->Plus(b.y);
    r.z = z->Plus(b.z);
    return r;
}

Expr *ExprVector::Dot(ExprVector b) {
    Expr *r;
    r =         x->Times(b.x);
    r = r->Plus(y->Times(b.y));
    r = r->Plus(z->Times(b.z));
    return r;
}

ExprVector ExprVector::Cross(ExprVector b) {
    ExprVector r;
    r.x = (y->Times(b.z))->Minus(z->Times(b.y));
    r.y = (z->Times(b.x))->Minus(x->Times(b.z));
    r.z = (x->Times(b.y))->Minus(y->Times(b.x));
    return r;
}

ExprVector ExprVector::ScaledBy(Expr *s) {
    ExprVector r;
    r.x = x->Times(s);
    r.y = y->Times(s);
    r.z = z->Times(s);
    return r;
}

ExprVector ExprVector::WithMagnitude(Expr *s) {
    Expr *m = Magnitude();
    return ScaledBy(s->Div(m));
}

Expr *ExprVector::Magnitude(void) {
    Expr *r;
    r =         x->Square();
    r = r->Plus(y->Square());
    r = r->Plus(z->Square());
    return r->Sqrt();
}

Vector ExprVector::Eval(void) {
    Vector r;
    r.x = x->Eval();
    r.y = y->Eval();
    r.z = z->Eval();
    return r;
}

ExprQuaternion ExprQuaternion::From(hParam w, hParam vx, hParam vy, hParam vz) {
    ExprQuaternion q;
    q.w  = Expr::From(w);
    q.vx = Expr::From(vx);
    q.vy = Expr::From(vy);
    q.vz = Expr::From(vz);
    return q;
}

ExprQuaternion ExprQuaternion::From(Expr *w, Expr *vx, Expr *vy, Expr *vz)
{
    ExprQuaternion q;
    q.w = w;
    q.vx = vx;
    q.vy = vy;
    q.vz = vz;
    return q;
}

ExprQuaternion ExprQuaternion::From(Quaternion qn) {
    ExprQuaternion qe;
    qe.w = Expr::From(qn.w);
    qe.vx = Expr::From(qn.vx);
    qe.vy = Expr::From(qn.vy);
    qe.vz = Expr::From(qn.vz);
    return qe;
}

ExprVector ExprQuaternion::RotationU(void) {
    ExprVector u;
    Expr *two = Expr::From(2);

    u.x = w->Square();
    u.x = (u.x)->Plus(vx->Square());
    u.x = (u.x)->Minus(vy->Square());
    u.x = (u.x)->Minus(vz->Square());

    u.y = two->Times(w->Times(vz));
    u.y = (u.y)->Plus(two->Times(vx->Times(vy)));

    u.z = two->Times(vx->Times(vz));
    u.z = (u.z)->Minus(two->Times(w->Times(vy)));

    return u;
}

ExprVector ExprQuaternion::RotationV(void) {
    ExprVector v;
    Expr *two = Expr::From(2);

    v.x = two->Times(vx->Times(vy));
    v.x = (v.x)->Minus(two->Times(w->Times(vz)));

    v.y = w->Square();
    v.y = (v.y)->Minus(vx->Square());
    v.y = (v.y)->Plus(vy->Square());
    v.y = (v.y)->Minus(vz->Square());

    v.z = two->Times(w->Times(vx));
    v.z = (v.z)->Plus(two->Times(vy->Times(vz)));

    return v;
}

ExprVector ExprQuaternion::RotationN(void) {
    ExprVector n;
    Expr *two = Expr::From(2);

    n.x =              two->Times( w->Times(vy));
    n.x = (n.x)->Plus (two->Times(vx->Times(vz)));

    n.y =              two->Times(vy->Times(vz));
    n.y = (n.y)->Minus(two->Times( w->Times(vx)));

    n.z =               w->Square();
    n.z = (n.z)->Minus(vx->Square());
    n.z = (n.z)->Minus(vy->Square());
    n.z = (n.z)->Plus (vz->Square());

    return n;
}

ExprVector ExprQuaternion::Rotate(ExprVector p) {
    // Express the point in the new basis
    return (RotationU().ScaledBy(p.x)).Plus(
            RotationV().ScaledBy(p.y)).Plus(
            RotationN().ScaledBy(p.z));
}

ExprQuaternion ExprQuaternion::Times(ExprQuaternion b) {
    Expr *sa = w, *sb = b.w;
    ExprVector va = { vx, vy, vz };
    ExprVector vb = { b.vx, b.vy, b.vz };

    ExprQuaternion r;
    r.w = (sa->Times(sb))->Minus(va.Dot(vb));
    ExprVector vr = vb.ScaledBy(sa).Plus(
                    va.ScaledBy(sb).Plus(
                    va.Cross(vb)));
    r.vx = vr.x;
    r.vy = vr.y;
    r.vz = vr.z;
    return r;
}

Expr *ExprQuaternion::Magnitude(void) {
    return ((w ->Square())->Plus(
            (vx->Square())->Plus(
            (vy->Square())->Plus(
            (vz->Square())))))->Sqrt();
}


Expr *Expr::From(hParam p) {
    Expr *r = AllocExpr();
    r->op = PARAM;
    r->x.parh = p;
    return r;
}

Expr *Expr::From(double v) {
    Expr *r = AllocExpr();
    r->op = CONSTANT;
    r->x.v = v;
    return r;
}

Expr *Expr::AnyOp(int newOp, Expr *b) {
    Expr *r = AllocExpr();
    r->op = newOp;
    r->a = this;
    r->b = b;
    return r;
}

int Expr::Children(void) {
    switch(op) {
        case PARAM:
        case PARAM_PTR:
        case CONSTANT:
            return 0;

        case PLUS:
        case MINUS:
        case TIMES:
        case DIV:
            return 2;

        case NEGATE:
        case SQRT:
        case SQUARE:
        case SIN:
        case COS:
        case ASIN:
        case ACOS:
            return 1;

        default: oops();
    }
}

int Expr::Nodes(void) {
    switch(Children()) {
        case 0: return 1;
        case 1: return 1 + a->Nodes();
        case 2: return 1 + a->Nodes() + b->Nodes();
        default: oops();
    }
}

Expr *Expr::DeepCopy(void) {
    Expr *n = AllocExpr();
    *n = *this;
    n->marker = 0;
    int c = n->Children();
    if(c > 0) n->a = a->DeepCopy();
    if(c > 1) n->b = b->DeepCopy();
    return n;
}

Expr *Expr::DeepCopyWithParamsAsPointers(IdList<Param,hParam> *firstTry,
    IdList<Param,hParam> *thenTry)
{
    Expr *n = AllocExpr();
    if(op == PARAM) {
        // A param that is referenced by its hParam gets rewritten to go
        // straight in to the parameter table with a pointer, or simply
        // into a constant if it's already known.
        Param *p = firstTry->FindByIdNoOops(x.parh);
        if(!p) p = thenTry->FindById(x.parh);
        if(p->known) {
            n->op = CONSTANT;
            n->x.v = p->val;
        } else {
            n->op = PARAM_PTR;
            n->x.parp = p;
        }
        return n;
    }

    *n = *this;
    int c = n->Children();
    if(c > 0) n->a = a->DeepCopyWithParamsAsPointers(firstTry, thenTry);
    if(c > 1) n->b = b->DeepCopyWithParamsAsPointers(firstTry, thenTry);
    return n;
}

double Expr::Eval(void) {
    switch(op) {
        case PARAM:         return SK.GetParam(x.parh)->val;
        case PARAM_PTR:     return (x.parp)->val;

        case CONSTANT:      return x.v;

        case PLUS:          return a->Eval() + b->Eval();
        case MINUS:         return a->Eval() - b->Eval();
        case TIMES:         return a->Eval() * b->Eval();
        case DIV:           return a->Eval() / b->Eval();

        case NEGATE:        return -(a->Eval());
        case SQRT:          return sqrt(a->Eval());
        case SQUARE:        { double r = a->Eval(); return r*r; }
        case SIN:           return sin(a->Eval());
        case COS:           return cos(a->Eval());
        case ACOS:          return acos(a->Eval());
        case ASIN:          return asin(a->Eval());

        default: oops();
    }
}

Expr *Expr::PartialWrt(hParam p) {
    Expr *da, *db;

    switch(op) {
        case PARAM_PTR: return From(p.v == x.parp->h.v ? 1 : 0);
        case PARAM:     return From(p.v == x.parh.v ? 1 : 0);

        case CONSTANT:  return From(0.0);

        case PLUS:      return (a->PartialWrt(p))->Plus(b->PartialWrt(p));
        case MINUS:     return (a->PartialWrt(p))->Minus(b->PartialWrt(p));

        case TIMES:
            da = a->PartialWrt(p);
            db = b->PartialWrt(p);
            return (a->Times(db))->Plus(b->Times(da));

        case DIV:           
            da = a->PartialWrt(p);
            db = b->PartialWrt(p);
            return ((da->Times(b))->Minus(a->Times(db)))->Div(b->Square());

        case SQRT:
            return (From(0.5)->Div(a->Sqrt()))->Times(a->PartialWrt(p));

        case SQUARE:
            return (From(2.0)->Times(a))->Times(a->PartialWrt(p));

        case NEGATE:    return (a->PartialWrt(p))->Negate();
        case SIN:       return (a->Cos())->Times(a->PartialWrt(p));
        case COS:       return ((a->Sin())->Times(a->PartialWrt(p)))->Negate();

        case ASIN:
            return (From(1)->Div((From(1)->Minus(a->Square()))->Sqrt()))
                        ->Times(a->PartialWrt(p));
        case ACOS:
            return (From(-1)->Div((From(1)->Minus(a->Square()))->Sqrt()))
                        ->Times(a->PartialWrt(p));

        default: oops();
    }
}

uint64_t Expr::ParamsUsed(void) {
    uint64_t r = 0;
    if(op == PARAM)     r |= ((uint64_t)1 << (x.parh.v % 61));
    if(op == PARAM_PTR) r |= ((uint64_t)1 << (x.parp->h.v % 61));

    int c = Children();
    if(c >= 1)          r |= a->ParamsUsed();
    if(c >= 2)          r |= b->ParamsUsed();
    return r;
}

bool Expr::DependsOn(hParam p) {
    if(op == PARAM)     return (x.parh.v    == p.v);
    if(op == PARAM_PTR) return (x.parp->h.v == p.v);

    int c = Children();
    if(c == 1)          return a->DependsOn(p);
    if(c == 2)          return a->DependsOn(p) || b->DependsOn(p);
    return false;
}

bool Expr::Tol(double a, double b) {
    return fabs(a - b) < 0.001;
}
Expr *Expr::FoldConstants(void) {
    Expr *n = AllocExpr();
    *n = *this;

    int c = Children();
    if(c >= 1) n->a = a->FoldConstants();
    if(c >= 2) n->b = b->FoldConstants();

    switch(op) {
        case PARAM_PTR:
        case PARAM:
        case CONSTANT:
            break;

        case MINUS:
        case TIMES:
        case DIV:
        case PLUS:
            // If both ops are known, then we can evaluate immediately
            if(n->a->op == CONSTANT && n->b->op == CONSTANT) {
                double nv = n->Eval();
                n->op = CONSTANT;
                n->x.v = nv;
                break;
            }
            // x + 0 = 0 + x = x
            if(op == PLUS && n->b->op == CONSTANT && Tol(n->b->x.v, 0)) {
                *n = *(n->a); break;
            }
            if(op == PLUS && n->a->op == CONSTANT && Tol(n->a->x.v, 0)) {
                *n = *(n->b); break;
            }
            // 1*x = x*1 = x
            if(op == TIMES && n->b->op == CONSTANT && Tol(n->b->x.v, 1)) {
                *n = *(n->a); break;
            }
            if(op == TIMES && n->a->op == CONSTANT && Tol(n->a->x.v, 1)) {
                *n = *(n->b); break;
            }
            // 0*x = x*0 = 0
            if(op == TIMES && n->b->op == CONSTANT && Tol(n->b->x.v, 0)) {
                n->op = CONSTANT; n->x.v = 0; break;
            }
            if(op == TIMES && n->a->op == CONSTANT && Tol(n->a->x.v, 0)) {
                n->op = CONSTANT; n->x.v = 0; break;
            }

            break;

        case SQRT:
        case SQUARE:
        case NEGATE:
        case SIN:
        case COS:
        case ASIN:
        case ACOS:
            if(n->a->op == CONSTANT) {
                double nv = n->Eval();
                n->op = CONSTANT;
                n->x.v = nv;
            }
            break;

        default: oops();
    }
    return n;
}

void Expr::Substitute(hParam oldh, hParam newh) {
    if(op == PARAM_PTR) oops();

    if(op == PARAM && x.parh.v == oldh.v) {
        x.parh = newh;
    }
    int c = Children();
    if(c >= 1) a->Substitute(oldh, newh);
    if(c >= 2) b->Substitute(oldh, newh);
}

//-----------------------------------------------------------------------------
// If the expression references only one parameter that appears in pl, then
// return that parameter. If no param is referenced, then return NO_PARAMS.
// If multiple params are referenced, then return MULTIPLE_PARAMS.
//-----------------------------------------------------------------------------
const hParam Expr::NO_PARAMS       = { 0 };
const hParam Expr::MULTIPLE_PARAMS = { 1 };
hParam Expr::ReferencedParams(ParamList *pl) {
    if(op == PARAM) {
        if(pl->FindByIdNoOops(x.parh)) {
            return x.parh;
        } else {
            return NO_PARAMS;
        }
    }
    if(op == PARAM_PTR) oops();

    int c = Children();
    if(c == 0) {
        return NO_PARAMS;
    } else if(c == 1) {
        return a->ReferencedParams(pl);
    } else if(c == 2) {
        hParam pa, pb;
        pa = a->ReferencedParams(pl);
        pb = b->ReferencedParams(pl);
        if(pa.v == NO_PARAMS.v) {
            return pb;
        } else if(pb.v == NO_PARAMS.v) {
            return pa;
        } else if(pa.v == pb.v) {
            return pa; // either, doesn't matter
        } else {
            return MULTIPLE_PARAMS;
        }
    } else oops();
}


//-----------------------------------------------------------------------------
// Routines to pretty-print an expression. Mostly for debugging.
//-----------------------------------------------------------------------------

static char StringBuffer[4096];
void Expr::App(const char *s, ...) {
    va_list f;
    va_start(f, s);
    vsprintf(StringBuffer+strlen(StringBuffer), s, f);
}
const char *Expr::Print(void) {
    if(!this) return "0";

    StringBuffer[0] = '\0';
    PrintW();
    return StringBuffer;
}

void Expr::PrintW(void) {
    char c;
    switch(op) {
        case PARAM:     App("param(%08x)", x.parh.v); break;
        case PARAM_PTR: App("param(p%08x)", x.parp->h.v); break;

        case CONSTANT:  App("%.3f", x.v); break;

        case PLUS:      c = '+'; goto p;
        case MINUS:     c = '-'; goto p;
        case TIMES:     c = '*'; goto p;
        case DIV:       c = '/'; goto p;
p:
            App("(");
            a->PrintW();
            App(" %c ", c);
            b->PrintW();
            App(")");
            break;

        case NEGATE:    App("(- "); a->PrintW(); App(")"); break;
        case SQRT:      App("(sqrt "); a->PrintW(); App(")"); break;
        case SQUARE:    App("(square "); a->PrintW(); App(")"); break;
        case SIN:       App("(sin "); a->PrintW(); App(")"); break;
        case COS:       App("(cos "); a->PrintW(); App(")"); break;
        case ASIN:      App("(asin "); a->PrintW(); App(")"); break;
        case ACOS:      App("(acos "); a->PrintW(); App(")"); break;

        default: oops();
    }
}


//-----------------------------------------------------------------------------
// A parser; convert a string to an expression. Infix notation, with the
// usual shift/reduce approach. I had great hopes for user-entered eq
// constraints, but those don't seem very useful, so right now this is just
// to provide calculator type functionality wherever numbers are entered.
//-----------------------------------------------------------------------------

#define MAX_UNPARSED 1024
static Expr *Unparsed[MAX_UNPARSED];
static int UnparsedCnt, UnparsedP;

static Expr *Operands[MAX_UNPARSED];
static int OperandsP;

static Expr *Operators[MAX_UNPARSED];
static int OperatorsP;

void Expr::PushOperator(Expr *e) {
    if(OperatorsP >= MAX_UNPARSED) throw "operator stack full!";
    Operators[OperatorsP++] = e;
}
Expr *Expr::TopOperator(void) {
    if(OperatorsP <= 0) throw "operator stack empty (get top)";
    return Operators[OperatorsP-1];
}
Expr *Expr::PopOperator(void) {
    if(OperatorsP <= 0) throw "operator stack empty (pop)";
    return Operators[--OperatorsP];
}
void Expr::PushOperand(Expr *e) {
    if(OperandsP >= MAX_UNPARSED) throw "operand stack full";
    Operands[OperandsP++] = e;
}
Expr *Expr::PopOperand(void) {
    if(OperandsP <= 0) throw "operand stack empty";
    return Operands[--OperandsP];
}
Expr *Expr::Next(void) {
    if(UnparsedP >= UnparsedCnt) return NULL;
    return Unparsed[UnparsedP];
}
void Expr::Consume(void) {
    if(UnparsedP >= UnparsedCnt) throw "no token to consume";
    UnparsedP++;
}

int Expr::Precedence(Expr *e) {
    if(e->op == ALL_RESOLVED) return -1; // never want to reduce this marker
    if(e->op != BINARY_OP && e->op != UNARY_OP) oops();

    switch(e->x.c) {
        case 'q':
        case 's':
        case 'c':
        case 'n':   return 30;

        case '*':
        case '/':   return 20;

        case '+':
        case '-':   return 10;

        default: oops();
    }
}

void Expr::Reduce(void) {
    Expr *a, *b;

    Expr *op = PopOperator();
    Expr *n;
    int o;
    switch(op->x.c) {
        case '+': o = PLUS;  goto c;
        case '-': o = MINUS; goto c;
        case '*': o = TIMES; goto c;
        case '/': o = DIV;   goto c;
c:
            b = PopOperand();
            a = PopOperand();
            n = a->AnyOp(o, b);
            break;

        case 'n': n = PopOperand()->Negate(); break;
        case 'q': n = PopOperand()->Sqrt(); break;
        case 's': n = (PopOperand()->Times(Expr::From(PI/180)))->Sin(); break;
        case 'c': n = (PopOperand()->Times(Expr::From(PI/180)))->Cos(); break;

        default: oops();
    }
    PushOperand(n);
}

void Expr::ReduceAndPush(Expr *n) {
    while(Precedence(n) <= Precedence(TopOperator())) {
        Reduce();
    }
    PushOperator(n);
}

void Expr::Parse(void) {
    Expr *e = AllocExpr();
    e->op = ALL_RESOLVED;
    PushOperator(e);

    for(;;) {
        Expr *n = Next();
        if(!n) throw "end of expression unexpected";
        
        if(n->op == CONSTANT) {
            PushOperand(n);
            Consume();
        } else if(n->op == PAREN && n->x.c == '(') {
            Consume();
            Parse();
            n = Next();
            if(n->op != PAREN || n->x.c != ')') throw "expected: )";
            Consume();
        } else if(n->op == UNARY_OP) {
            PushOperator(n);
            Consume();
            continue;
        } else if(n->op == BINARY_OP && n->x.c == '-') {
            // The minus sign is special, because it might be binary or
            // unary, depending on context.
            n->op = UNARY_OP;
            n->x.c = 'n';
            PushOperator(n);
            Consume();
            continue;
        } else {
            throw "expected expression";
        }

        n = Next();
        if(n && n->op == BINARY_OP) {
            ReduceAndPush(n);
            Consume();
        } else {
            break;
        }
    }

    while(TopOperator()->op != ALL_RESOLVED) {
        Reduce();
    }
    PopOperator(); // discard the ALL_RESOLVED marker
}

void Expr::Lex(const char *in) {
    while(*in) {
        if(UnparsedCnt >= MAX_UNPARSED) throw "too long";

        char c = *in;
        if(isdigit(c) || c == '.') {
            // A number literal
            char number[70];
            int len = 0;
            while((isdigit(*in) || *in == '.') && len < 30) {
                number[len++] = *in;
                in++;
            }
            number[len++] = '\0';
            Expr *e = AllocExpr();
            e->op = CONSTANT;
            e->x.v = atof(number);
            Unparsed[UnparsedCnt++] = e;
        } else if(isalpha(c) || c == '_') {
            char name[70];
            int len = 0;
            while(isforname(*in) && len < 30) {
                name[len++] = *in;
                in++;
            }
            name[len++] = '\0';

            Expr *e = AllocExpr();
            if(strcmp(name, "sqrt")==0) {
                e->op = UNARY_OP;
                e->x.c = 'q';
            } else if(strcmp(name, "cos")==0) {
                e->op = UNARY_OP;
                e->x.c = 'c';
            } else if(strcmp(name, "sin")==0) {
                e->op = UNARY_OP;
                e->x.c = 's';
            } else {
                throw "unknown name";
            }
            Unparsed[UnparsedCnt++] = e;
        } else if(strchr("+-*/()", c)) {
            Expr *e = AllocExpr();
            e->op = (c == '(' || c == ')') ? PAREN : BINARY_OP;
            e->x.c = c;
            Unparsed[UnparsedCnt++] = e;
            in++;
        } else if(isspace(c)) {
            // Ignore whitespace
            in++;
        } else {
            // This is a lex error.
            throw "unexpected characters";
        }
    }
}

Expr *Expr::From(const char *in, bool popUpError) {
    UnparsedCnt = 0;
    UnparsedP = 0;
    OperandsP = 0;
    OperatorsP = 0;

    Expr *r;
    try {
        Lex(in);
        Parse();
        r = PopOperand();
    } catch (char *e) {
        dbp("exception: parse/lex error: %s", e);
        if(popUpError) {
            Error("Not a valid number or expression: '%s'", in);
        }
        return NULL;
    }
    return r;
}