Initializing ap_[u]fixpt Types

The ap_[u]fixpt types can be constructed and assigned from other fixed points, the ap_[u]int types, C++ integer and floating point types, as well as concatenations and bit selections. They can also be initialized from a hexadecimal string describing the exact bits. Note that construction and assignment will always trigger the quantization and overflow handling of the ap_[u]fixpt being constructed or assigned to, except when copying from the exact same type, or initializing from a hexadecimal string. For logical assignments of bits, bit selection assignments can be used, as well as the from_raw_bits function, or the ap_[u]int to_fixpt<I_W>() functions in the case of ap_[u]int types.

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Initializing ap_[u]fixpt types from floating point types in hardware is expensive, and should be avoided when possible. However, initializing ap_[u]fixpt from floating point literals is free, and happens at compile time.

Some examples of initializing fixed point types are shown in the following code snippet.
#include "hls/ap_int.hpp"
#include "hls/ap_fixpt.hpp"
#include <iostream>
#include <stdio.h>

using namespace hls;

    //...
    // Initialized to -13.75
    ap_fixpt<8, 4> fixed1 = -13.75;
    std::cout << "fixed1 = " << fixed1 << std::endl;
    // Initialized to 135
    ap_ufixpt<8, 8> fixed2 = 135;
    std::cout << "fixed2 = " << fixed2 << std::endl;
    // Initialized to -112
    // Could also write "0x9"
    // 0x is optional
    ap_fixpt<4, 8> fixed3("9");
    std::cout << "fixed3 = " << fixed3 << std::endl;
    // Initialized to 14
    ap_ufixpt<10, 4> fixed4 = ap_uint<16>(14);
    std::cout << "fixed4 = " << fixed4 << std::endl;
    // Initialized to -1 (AP_SAT triggered)
    ap_fixpt<4, 1, AP_TRN, AP_SAT> fixed5 = -4;
    std::cout << "fixed5 = " << fixed5 << std::endl;
    // Initialized to 1.5 (AP_RND triggered)
    ap_ufixpt<4, 3, AP_RND> fixed6 = 1.25;
    std::cout << "fixed6 = " << fixed6 << std::endl;
    // Initialized to 15.75 from a logical string of bits
    ap_ufixpt<8, 4> fixed7;
    fixed7(7, 0) = ap_uint<8>("FC");
    std::cout << "fixed7 = " << fixed7 << std::endl;
    // Assign an existing ap_uint variable to an ap_ufixpt variable
    ap_uint<8> ap_uint_var = 15;
    ap_ufixpt<8, 4> fixed8;
    fixed8(7, 0) = ap_uint_var;
    std::cout << "fixed8 = " << fixed8 << std::endl;
    // Initialize to 13 from a logical string of bits
    ap_fixpt<6, 5> fixed9;
    fixed9.from_raw_bits(ap_uint<6>(26));
    std::cout << "fixed9 = " << fixed9 << std::endl;
    // Initialize to -32 from a logical string of bits
    // (First convert ap_uint<4> to ap_fixpt<4, 6> logically,
    // then perform fixed point assignment)
    ap_fixpt<1, 6> fixed10 = ap_uint<4>("8").to_fixpt<6>();
    std::cout << "fixed10 = " << fixed10 << std::endl;
    // Initialize to 32 from a logical string of bits
    // (First convert ap_int<4> to ap_ufixpt<4, 6> logically,
    // then perform fixed point assignment)
    ap_ufixpt<1, 6> fixed11 = ap_int<4>("8").to_ufixpt<6>();
    std::cout << "fixed11 = " << fixed1 << std::endl;