Text and Parsing Utilities

Extract Prefix

substr copies part of a string, which is useful when a record has a fixed prefix.

substr `substr(start, count)` returns a new string starting at `start` with at most `count` characters.
prefix A prefix is the leading part of a string.

Extract Prefix

width
extract_prefix.cpp
Replay: real traced execution (multi-file project)
#include <iostream>
#include <string>

int main() {
    int width = 3;

    std::string code = "INV-2048";
    std::string prefix = code.substr(0, width);
    int size = static_cast<int>(prefix.size());

    std::cout << "prefix=" << prefix << std::endl;
    std::cout << "size=" << size << std::endl;
    return 0;
}

#include <iostream>
#include <string>

int main() {
    int width = 2;

    std::string code = "INV-2048";
    std::string prefix = code.substr(0, width);
    int size = static_cast<int>(prefix.size());

    std::cout << "prefix=" << prefix << std::endl;
    std::cout << "size=" << size << std::endl;
    return 0;
}

#include <iostream>
#include <string>

int main() {
    int width = 5;

    std::string code = "INV-2048";
    std::string prefix = code.substr(0, width);
    int size = static_cast<int>(prefix.size());

    std::cout << "prefix=" << prefix << std::endl;
    std::cout << "size=" << size << std::endl;
    return 0;
}

  1. width ← 3, code ← INV-2048, prefix ← INV, size ← 3

    4int main() {5    int width→ 3 = 3; //@width=2, 567    std::string code→ INV-2048 = "INV-2048";8    std::string prefix→ INV = codeINV-2048.substr(0, width3);9    int size→ 3 = static_cast<int>(prefixINV.size());1011    std::cout << "prefix=" << prefixINV << std::endl;12    std::cout << "size=" << size3 << std::endl;13    return 0;14}
    outputprefix=INV
size=3

  1. width ← 2, code ← INV-2048, prefix ← IN, size ← 2

    4int main() {5    int width→ 2 = 2;67    std::string code→ INV-2048 = "INV-2048";8    std::string prefix→ IN = codeINV-2048.substr(0, width2);9    int size→ 2 = static_cast<int>(prefixIN.size());1011    std::cout << "prefix=" << prefixIN << std::endl;12    std::cout << "size=" << size2 << std::endl;13    return 0;14}
    outputprefix=IN
size=2

  1. width ← 5, code ← INV-2048, prefix ← INV-2, size ← 5

    4int main() {5    int width→ 5 = 5;67    std::string code→ INV-2048 = "INV-2048";8    std::string prefix→ INV-2 = codeINV-2048.substr(0, width5);9    int size→ 5 = static_cast<int>(prefixINV-2.size());1011    std::cout << "prefix=" << prefixINV-2 << std::endl;12    std::cout << "size=" << size5 << std::endl;13    return 0;14}
    outputprefix=INV-2
size=5