C++ API Reference

Complete reference documentation for the Z3 C++ API. All classes are in the z3 namespace.

Core Classes

z3::context

Manages all Z3 objects and global configuration. Every Z3 object is associated with a context.

Constructor

z3::context()
z3::context(z3::config& cfg)

Create a new Z3 context, optionally with custom configuration. Example:

z3::context c;

// With configuration
z3::config cfg;
cfg.set("timeout", 30000);
z3::context c2(cfg);

Sort Creation Methods

z3::sort bool_sort();
z3::sort int_sort();
z3::sort real_sort();
z3::sort bv_sort(unsigned sz);
z3::sort string_sort();
z3::sort array_sort(sort d, sort r);
z3::sort fpa_sort(unsigned ebits, unsigned sbits);

Create various sorts (types) for expressions. Example:

z3::context c;
z3::sort i = c.int_sort();           // Integer sort
z3::sort bv32 = c.bv_sort(32);       // 32-bit bitvector
z3::sort arr = c.array_sort(i, i);   // Int -> Int array

Constant Creation Methods

z3::expr bool_const(char const* name);
z3::expr int_const(char const* name);
z3::expr real_const(char const* name);
z3::expr bv_const(char const* name, unsigned sz);
z3::expr constant(char const* name, sort const& s);

Create named constants of various types. Example:

z3::context c;
z3::expr b = c.bool_const("b");       // Boolean variable
z3::expr x = c.int_const("x");        // Integer variable
z3::expr bv = c.bv_const("bv", 16);   // 16-bit bitvector

Value Creation Methods

z3::expr bool_val(bool b);
z3::expr int_val(int n);
z3::expr int_val(char const* n);
z3::expr real_val(int n, int d);        // Fraction n/d
z3::expr real_val(char const* n);
z3::expr bv_val(int n, unsigned sz);
z3::expr string_val(char const* s);

Create concrete values. Example:

z3::context c;
z3::expr t = c.bool_val(true);
z3::expr forty_two = c.int_val(42);
z3::expr half = c.real_val(1, 2);     // 1/2
z3::expr pi = c.real_val("3.14159");

Function Declaration

z3::func_decl function(char const* name, sort const& domain, sort const& range);
z3::func_decl function(char const* name, unsigned arity, sort const* domain, sort const& range);
z3::func_decl function(char const* name, sort_vector const& domain, sort const& range);

Declare uninterpreted functions. Example:

z3::context c;
z3::sort I = c.int_sort();

// f: Int -> Int
z3::func_decl f = c.function("f", I, I);

z3::expr x = c.int_const("x");
z3::expr fx = f(x);  // Apply function to x

Configuration

void set(char const* param, char const* value);
void set(char const* param, bool value);
void set(char const* param, int value);

Update context parameters. Example:

z3::context c;
c.set("timeout", 5000);     // 5 second timeout
c.set("auto_config", true);

Parsing

z3::expr_vector parse_string(char const* s);
z3::expr_vector parse_file(char const* file);

Parse SMT-LIB2 format strings or files.

z3::solver

The main interface for solving constraints.

Constructor

z3::solver(z3::context& c);
z3::solver(z3::context& c, char const* logic);

Create a solver, optionally for a specific logic (e.g., “QF_LIA” for quantifier-free linear integer arithmetic). Example:

z3::context c;
z3::solver s(c);

// Solver for specific logic
z3::solver s2(c, "QF_BV");  // Bitvectors

Adding Constraints

void add(expr const& e);
void add(expr const& e, expr const& p);  // Track with proof literal
void add(expr const& e, char const* p);  // Track with named literal
void add(expr_vector const& v);

Add constraints to the solver. Example:

z3::context c;
z3::solver s(c);
z3::expr x = c.int_const("x");

s.add(x > 0);
s.add(x < 10);

// Tracked assertion for unsat cores
s.add(x < 5, "p1");

Checking Satisfiability

z3::check_result check();
z3::check_result check(unsigned n, expr const* assumptions);
z3::check_result check(expr_vector const& assumptions);

Check if the current set of constraints is satisfiable. Returns: z3::sat, z3::unsat, or z3::unknown Example:

z3::context c;
z3::solver s(c);
z3::expr x = c.int_const("x");

s.add(x > 0);

if (s.check() == z3::sat) {
    std::cout << "Satisfiable!\n";
} else if (s.check() == z3::unsat) {
    std::cout << "Unsatisfiable!\n";
}

Extracting Models

z3::model get_model() const;

Retrieve a model when the constraints are satisfiable. Example:

z3::context c;
z3::solver s(c);
z3::expr x = c.int_const("x");

s.add(x >= 1 && x <= 10);

if (s.check() == z3::sat) {
    z3::model m = s.get_model();
    std::cout << "x = " << m.eval(x) << "\n";
}

Backtracking

void push();
void pop(unsigned n = 1);
void reset();

Manage the assertion stack for incremental solving. Example:

z3::context c;
z3::solver s(c);
z3::expr x = c.int_const("x");

s.add(x > 0);
s.push();           // Save state
s.add(x < 0);       // Add conflicting constraint
s.check();          // unsat
s.pop();            // Restore to saved state
s.check();          // sat again

Getting Information

z3::expr_vector assertions() const;
z3::expr_vector unsat_core() const;
z3::stats statistics() const;
std::string reason_unknown() const;
std::string to_smt2(char const* status = "unknown");

Retrieve information about the solver state. Example:

z3::solver s(c);
s.add(x > 0);
s.add(x < 0, "p1");

if (s.check() == z3::unsat) {
    z3::expr_vector core = s.unsat_core();
    std::cout << "Unsat core: " << core << "\n";
}

z3::expr

Represents formulas and terms. This is the main class for building expressions.

Type Checking

bool is_bool() const;
bool is_int() const;
bool is_real() const;
bool is_arith() const;
bool is_bv() const;
bool is_array() const;
bool is_numeral() const;
bool is_app() const;
bool is_const() const;
bool is_quantifier() const;

Check the type and kind of expression. Example:

z3::context c;
z3::expr x = c.int_const("x");

if (x.is_int()) {
    std::cout << "x is an integer\n";
}

Getting Information

z3::sort get_sort() const;
z3::context& ctx() const;
unsigned id() const;
unsigned hash() const;

Retrieve properties of the expression. Example:

z3::context c;
z3::expr x = c.int_const("x");
z3::sort s = x.get_sort();
std::cout << "Sort: " << s << "\n";

Extracting Numeral Values

bool is_numeral_i(int& i) const;
bool is_numeral_u(unsigned& i) const;
bool is_numeral_i64(int64_t& i) const;
bool is_numeral_u64(uint64_t& i) const;
bool is_numeral(std::string& s) const;
int get_numeral_int() const;
uint64_t get_numeral_uint64() const;

Extract numeric values from numeral expressions. Example:

z3::context c;
z3::expr val = c.int_val(42);

if (val.is_numeral()) {
    int n = val.get_numeral_int();
    std::cout << "Value: " << n << "\n";
}

Application Information

z3::func_decl decl() const;        // requires is_app()
unsigned num_args() const;         // requires is_app()
z3::expr arg(unsigned i) const;    // requires is_app()
z3::expr_vector args() const;      // requires is_app()

Access parts of an application expression. Example:

z3::context c;
z3::expr x = c.int_const("x");
z3::expr y = c.int_const("y");
z3::expr sum = x + y;

if (sum.is_app()) {
    unsigned n = sum.num_args();     // 2
    z3::expr arg0 = sum.arg(0);      // x
    z3::expr arg1 = sum.arg(1);      // y
}

Simplification

z3::expr simplify() const;
z3::expr simplify(params const& p) const;

Simplify the expression. Example:

z3::context c;
z3::expr x = c.int_const("x");
z3::expr e = x + 0;
z3::expr simple = e.simplify();  // Returns just x

Substitution

z3::expr substitute(expr_vector const& src, expr_vector const& dst);
z3::expr substitute(expr_vector const& dst);

Perform substitution on the expression.

z3::model

Represents a satisfying assignment (model) for a set of constraints.

Evaluating Expressions

z3::expr eval(expr const& e, bool model_completion = false) const;

Evaluate an expression in the model. Example:

z3::context c;
z3::solver s(c);
z3::expr x = c.int_const("x");
z3::expr y = c.int_const("y");

s.add(x > 0 && y == x + 1);

if (s.check() == z3::sat) {
    z3::model m = s.get_model();
    std::cout << "x = " << m.eval(x) << "\n";
    std::cout << "y = " << m.eval(y) << "\n";
    std::cout << "x + y = " << m.eval(x + y) << "\n";
}

Inspecting the Model

unsigned size() const;
z3::func_decl operator[](unsigned i) const;
z3::expr get_const_interp(func_decl const& c) const;

Iterate over the model’s assignments. Example:

z3::model m = s.get_model();

for (unsigned i = 0; i < m.size(); i++) {
    z3::func_decl v = m[i];
    std::cout << v.name() << " = " 
              << m.get_const_interp(v) << "\n";
}

Operator Overloading

The C++ API provides natural operator syntax for building expressions.

Boolean Operators

expr operator!(expr const& a);                  // NOT
expr operator&&(expr const& a, expr const& b);  // AND
expr operator||(expr const& a, expr const& b);  // OR
expr operator==(expr const& a, expr const& b);  // Equality
expr operator!=(expr const& a, expr const& b);  // Disequality
expr implies(expr const& a, expr const& b);     // Implication

Example:

z3::context c;
z3::expr p = c.bool_const("p");
z3::expr q = c.bool_const("q");

z3::expr formula = (!p || q) && (p || !q);

Arithmetic Operators

expr operator+(expr const& a, expr const& b);   // Addition
expr operator-(expr const& a, expr const& b);   // Subtraction
expr operator-(expr const& a);                   // Negation
expr operator*(expr const& a, expr const& b);   // Multiplication
expr operator/(expr const& a, expr const& b);   // Division
expr operator%(expr const& a, expr const& b);   // Modulo

Example:

z3::context c;
z3::expr x = c.int_const("x");
z3::expr y = c.int_const("y");

z3::expr formula = 2*x + 3*y == 10;

Comparison Operators

expr operator<(expr const& a, expr const& b);
expr operator<=(expr const& a, expr const& b);
expr operator>(expr const& a, expr const& b);
expr operator>=(expr const& a, expr const& b);

Example:

z3::context c;
z3::expr x = c.int_const("x");
z3::expr y = c.int_const("y");

z3::expr constraint = (x >= 0) && (x < 10) && (x < y);

Bitvector Operators

expr operator&(expr const& a, expr const& b);   // Bitwise AND
expr operator|(expr const& a, expr const& b);   // Bitwise OR
expr operator^(expr const& a, expr const& b);   // Bitwise XOR
expr operator~(expr const& a);                   // Bitwise NOT
expr extract(unsigned hi, unsigned lo) const;    // Bit extraction

Example:

z3::context c;
z3::expr x = c.bv_const("x", 8);  // 8-bit
z3::expr y = c.bv_const("y", 8);

z3::expr formula = (x & y) == c.bv_val(0, 8);
z3::expr low_nibble = x.extract(3, 0);

Helper Functions

Quantifiers

expr forall(expr const& x, expr const& body);
expr forall(expr_vector const& xs, expr const& body);
expr exists(expr const& x, expr const& body);
expr exists(expr_vector const& xs, expr const& body);

Create quantified formulas. Example:

z3::context c;
z3::expr x = c.int_const("x");
z3::expr y = c.int_const("y");
z3::sort I = c.int_sort();
z3::func_decl f = c.function("f", I, I, I);

// forall x, y: f(x, y) >= 0
z3::expr formula = forall(x, forall(y, f(x, y) >= 0));

Array Operations

expr select(expr const& a, expr const& i);
expr store(expr const& a, expr const& i, expr const& v);
expr const_array(sort const& s, expr const& v);

Manipulate array expressions. Example:

z3::context c;
z3::sort I = c.int_sort();
z3::sort A = c.array_sort(I, I);

z3::expr a = c.constant("a", A);
z3::expr i = c.int_const("i");
z3::expr v = c.int_const("v");

z3::expr read = select(a, i);
z3::expr updated = store(a, i, v);

Other Helpers

expr ite(expr const& c, expr const& t, expr const& e);  // if-then-else
expr distinct(expr_vector const& args);                  // All different
expr concat(expr const& a, expr const& b);               // Concatenate
expr mk_and(expr_vector const& args);                    // N-ary AND
expr mk_or(expr_vector const& args);                     // N-ary OR

Additional Classes

z3::config

Configuration object for context creation.

z3::config cfg;
cfg.set("timeout", 5000);
cfg.set("auto_config", true);
z3::context c(cfg);

z3::params

Parameters for solvers and tactics.

z3::params p(c);
p.set("unsat_core", true);
p.set("timeout", 30000);
s.set(p);

z3::expr_vector

Vector of expressions.

z3::expr_vector v(c);
v.push_back(x);
v.push_back(y);
unsigned sz = v.size();
z3::expr e = v[0];

z3::sort_vector

Vector of sorts.

z3::sort_vector sv(c);
sv.push_back(c.int_sort());
sv.push_back(c.bool_sort());

Next Steps

Getting Started Guide - Learn basic usage patterns
Core Concepts - Theory and advanced topics
Examples - Complete example programs

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​C++ API Reference

​Core Classes

​z3::context

​Constructor

​Sort Creation Methods

​Constant Creation Methods

​Value Creation Methods

​Function Declaration

​Configuration

​Parsing

​z3::solver

​Constructor

​Adding Constraints

​Checking Satisfiability

​Extracting Models

​Backtracking

​Getting Information

​z3::expr

​Type Checking

​Getting Information

​Extracting Numeral Values

​Application Information

​Simplification

​Substitution

​z3::model

​Evaluating Expressions

​Inspecting the Model

​Operator Overloading

​Boolean Operators

​Arithmetic Operators

​Comparison Operators

​Bitvector Operators

​Helper Functions

​Quantifiers

​Array Operations

​Other Helpers

​Additional Classes

​z3::config

​z3::params

​z3::expr_vector

​z3::sort_vector

​Next Steps

Build docs developers (and LLMs) love

C++ API Reference

Core Classes

z3::context

Constructor

Sort Creation Methods

Constant Creation Methods

Value Creation Methods

Function Declaration

Configuration

Parsing

z3::solver

Constructor

Adding Constraints

Checking Satisfiability

Extracting Models

Backtracking

Getting Information

z3::expr

Type Checking

Getting Information

Extracting Numeral Values

Application Information

Simplification

Substitution

z3::model

Evaluating Expressions

Inspecting the Model

Operator Overloading

Boolean Operators

Arithmetic Operators

Comparison Operators

Bitvector Operators

Helper Functions

Quantifiers

Array Operations

Other Helpers

Additional Classes

z3::config

z3::params

z3::expr_vector

z3::sort_vector

Next Steps