Ошибка expected primary expression before token

И что такое

if (p1 > 0 && p2 > 0) || (p1 < 0 && p2 < 0);

Инструкция if имеет вид

if ( условие )  { что-то-там } [else { что-то-там-еще }] 

У вас одно условие без скобок и без инструкций для выполнения… По сути —

if условие 

Вот как должен выглядеть ваш код:

#include <iostream>
#include <math.h>

using namespace std;
int main()
{
    int a, b, c, d, s, t, u, p, p1, p2;
    s != 0;
    t != 0;
    cout << "Vvedite a,b,c,d,s,t,u " << endl;
    cin >> a >> b >> c >> d >> s >> t >> u;
    p1 = sa + tb + u;
    p2 = sc + td + u;

    if ((p1 > 0 && p2 > 0) || (p1 < 0 && p2 < 0))
    {
        cout << "Nalezat odniy ploschini" << endl;
        return 0;
    }

    if ((p1 < 0 && p2 > 0) || (p1 > 0 && p2 < 0))
    {
        cout << "Nalezat riznim ploschinam" << endl;
        return 0;
    }
}

Кстати, обратите внимание на угловые скобки <> в директивах #include!

“Expected primary-expression before ‘some‘ token” is one of the most common errors that you can experience in Arduino code. Arduino code is written in C++ with few additions here and there, so it is a C++ syntax error. There are multiple versions of this error, depends on what is it that you messed up. Some are easy to fix, some not so much.

Most of the times (but not always), the error occurs because you have missed something or put it at the wrong place. Be it a semicolon, a bracket or something else. It can be fixed by figuring out what is that you missed/misplaced and placing it at the right position. Let us walk through multiple versions of the error and how to fix them one by one.

We all like building things, don’t we? Arduino gives us the opportunity to do amazing things with electronics with simply a little bit of code. It is an open-source electronics platform. It is based on hardware and software which are easy to learn and use. If I were to explain in simple language what Arduino does – it takes an input from the user in different forms such as touch or light and turns it into an output such as running a motor. Actually, you can even post tweets on Twitter with Arduino.

I’ll walk you through multiple examples of where the error can occur and how to possibly fix it. The codes that I use as examples in this article are codes that people posted on forums asking for a solution, so all credits of the code go to them. Let’s begin.

Type 1: Expected primary-expression before ‘}’ token

This error occurs when when the opening curly brackets ‘{‘ are not properly followed by the closing curly bracket ‘}’. To fix this, what you have to do is: check if all of your opening and closing curly brackets match properly. Also, check if you are missing any curly brackets. There isn’t much to this, so I’ll move on to the other types.

Type 2: Expected primary expression before ‘)’ token

Example 1: All credits to this thread. Throughout all of my examples, I will highlight the line which is causing the issue with red.

#include <Adafruit_NeoPixel.h>
#include <BlynkSimpleEsp8266.h>
#include <ESP8266WiFi.h>
#define PIN D1
#define NUMPIXELS 597
int red = 0;
int green = 0;
int blue = 0;
int game = 0;
  Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
///////////////////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
  Blynk.begin("d410a13b55560fbdfb3df5fe2a2ff5", "8", "12345670");
  pixels.begin();
  pixels.show();
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////
BLYNK_WRITE(V1) {
  game = 1;
  int R = param[0].asInt();
  int G = param[1].asInt();
  int B = param[2].asInt();
  setSome(R, G, B);
}
BLYNK_WRITE(V2) {
  if (param.asInt()==1) {
    game = 2;
    rainbow(uint8_t); // Rainbow
  }
  else {
  }
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////
void loop()
{
Blynk.run();
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////
void rainbow(uint8_t wait) {
  uint16_t i, j;
  for(j=0; j<256; j++) {
    for(i=0; i<NUMPIXELS; i++) {
      pixels.setPixelColor(i, Wheel((i+j) & 255));
    }
    pixels.show();
    delay(wait);
  }
 // delay(1);
}
uint32_t Wheel(byte WheelPos) {
  WheelPos = 255 - WheelPos;
  if(WheelPos < 85) {
    return pixels.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  }
  if(WheelPos < 170) {
    WheelPos -= 85;
    return pixels.Color(0, WheelPos * 3, 255 - WheelPos * 3);
  }
  WheelPos -= 170;
  return pixels.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
}BLYNK_WRITE(V3) {
  if (param.asInt()) {
    game = 3;
    setAll(125, 47, 0); //candle
  }
  else {
  }
}
BLYNK_WRITE(V4) {
  game = 4;
  int Bright = param.asInt();
  pixels.setBrightness(Bright);
  pixels.show();
}
BLYNK_WRITE(V5) {
  if (param.asInt()) {
    game = 5;
    setAll(85, 0, 255);
  }
  else {
  }
}
BLYNK_WRITE(V6) {
  if (param.asInt()) {
    game = 6;
    oFF(red, green, blue);
//    fullOff();
  }
  else {
  }
}
BLYNK_WRITE(V7) {
  if (param.asInt()) {
    game = 7;
    setAll(255, 0, 85);
  }
  else {
  }
}
BLYNK_WRITE(V8) {
  if (param.asInt()) {
    game = 8;
    setAll(90, 90, 90);
  }
  else {
  }
}
BLYNK_WRITE(V9) {
  if (param.asInt()) {
    game = 9;
    setAll(255, 130, 130);
  }
  else {
  }
}


////////////////////////////////////////////////////////////////////////////////////////////////////////////
void oFF(byte r, byte g, byte b) {
  if (game == 1) {
    offsome(r, g, b);
  }
  else if (game == 2) {
    offall(r, g, b);
  }
  else if (game == 3) {
    offall(r, g, b);
  }
  else if (game == 4) {
    offall(r, g, b);
  }
  else if (game == 5) {
    offall(r, g, b);
  }
  else if (game == 6) {
    offall(r, g, b);
  }
  else if (game == 7) {
    offall(r, g, b);
  }
  else if (game == 8) {
    offall(r, g, b);
  }
  else if (game == 9) {
    offall(r, g, b);
  }
}

void offall(byte r, byte g, byte b) {
  uint32_t x = r, y = g, z = b;
  for (x; x > 0; x--) {
    if( y > 0 )
      y--;
    if( z > 0 )
      z--;
    for(int i = 0; i < NUMPIXELS; i++ ) {
      pixels.setPixelColor(i, pixels.Color(x, y, z));
    }
    pixels.show();
    delay(0);
  }
  //delay(0);
}

void offsome(byte r, byte g, byte b) {
  uint32_t x = r, y = g, z = b;
  for (x; x > 0; x--) {
    if( y > 0 )
      y--;
    if( z > 0 )
      z--;
    for(int i = 87; i < 214; i++ ) {
      pixels.setPixelColor(i, pixels.Color(x, y, z));
    }
    for(int i = 385; i < 510; i++ ) {
      pixels.setPixelColor(i, pixels.Color(x, y, z));
    }
    pixels.show();
    delay(0);
  }
}
void setAll(byte r, byte g, byte b) {
  uint16_t x = 0, y = 0, z = 0;
  for (x; x < r; x++) {
    if( y < g )
      y++;
    if( z < b )
      z++;
    for(int i = 0; i < NUMPIXELS; i++ ) {
      pixels.setPixelColor(i, pixels.Color(x, y, z));
    }
    pixels.show();
    red = r;
    green = g;
    blue = b;
    delay(0);
  }
  //delay(0);
}

void setSome(byte r, byte g, byte b) {
  uint16_t x = 0, y = 0, z = 0;
  for (x; x < r; x++) {
    if( y < g )
      y++;
    if( z < b )
      z++;
    for(int i = 86; i < 212; i++ ) {
      pixels.setPixelColor(i, pixels.Color(x, y, z));
    }
    for(int i = 385; i < 512; i++ ) {
      pixels.setPixelColor(i, pixels.Color(x, y, z));
    }
    pixels.show();
    red = r;
    green = g;
    blue = b;
    delay(0);
  }
  //delay(0);
}

void fullOff() {
  for(int i = 0; i < NUMPIXELS; i++ ) {
    pixels.setPixelColor(i, pixels.Color(0, 0, 0));
  }
    pixels.show();
}

Solution 1:

The error occurs in this code because the rainbow function is supposed to have a variable as its argument, however the argument given here is ‘uint8_t’ which is not a variable.

BLYNK_WRITE(V2) {
  if (param.asInt()==1) {
    game = 2;
    rainbow(uint8_t); // Rainbow
  }
  else {
  }
}

Here all you have to do is define uint8_t as a variable first and assign it a value. The code will work after that.

Type 3: Expected primary-expression before ‘enum’

Example 1: All credits to this thread.

#include <iostream>

using namespace std;

int main()
{
     enum userchoice
    {
        Toyota = 1,
        Lamborghini,
        Ferrari,
        Holden,
        Range Rover
    };
    
    enum quizlevels
    {
        Hardquestions = 1,
        Mediumquestions, 
        Easyquestions
    };  

    return 0;
}

Solution 1:

The “expected primary-expression before ‘enum’ ” error occurs here because the enum here has been defined inside a method, which is incorrect. The corrected code is:

#include <iostream>

using namespace std;


enum userchoice
    {
    Toyota = 1,
    Lamborghini,
    Ferrari,
    Holden,
    RangeRover
    };

enum quizlevels
    {
    HardQuestions = 1,
    MediumQuestions,
    EasyQuestions
    };

int main()
    {
    return 0;
    }

Note: Another mistake has been fixed in this code i.e. the space in “Range Rover” variable. Variable names cannot contain spaces.

Type 4: Expected primary expression before ‘.’

Example 1: All credits go to this thread.

#include <iostream>
using std::cout;
using std::endl;

class square {

public:
    double length, width;
    
    square(double length, double width);
    square();
    
    ~square();
    
    double perimeter();
};

double square::perimeter() {
return 2*square.length + 2*square.width;
}

int main() {

square sq(4.0, 4.0);

cout << sq.perimeter() << endl;

return 0;
}

Solution 1: Here the error occurs because “square” is being used as an object, which it is not. Square is a type, and the corrected code is given below.

#include <iostream>
using std::cout;
using std::endl;

class square {

public:
    double length, width;
    
    square(double length, double width);
    square();
    
    ~square();
    
    double perimeter();
};

double square::perimeter() {
return 2*length + 2*width;
}

int main() {

square sq(4.0, 4.0);

cout << sq.perimeter() << endl;

return 0;
}

Type 5: Expected primary-expression before ‘word’

Example 1: All credits go to this thread.

#include <iostream>
#include <string>
using namespace std;

string userInput();
int wordLengthFunction(string word);
int permutation(int wordLength);

int main()
{
    string word = userInput();
    int wordLength = wordLengthFunction(string word);

    cout << word << " has " << permutation(wordLength) << " permutations." << endl;
    
    return 0;
}

string userInput()
{
    string word;

    cout << "Please enter a word: ";
    cin >> word;

    return word;
}
int wordLengthFunction(string word)
{
    int wordLength;

    wordLength = word.length();

    return wordLength;
}

int permutation(int wordLength)
{    
    if (wordLength == 1)
    {
        return wordLength;
    }
    else
    {
        return wordLength * permutation(wordLength - 1);
    }    
}

Solution 1:

Here, they are incorrectly using string inside wordLengthFunction().

Fixing it is simple, simply replace

int wordLength = wordLengthFunction(string word);

by

int wordLength = wordLengthFunction(word);

Type 6: Expected primary-expression before ‘else’

Example 1: All credit goes to this thread.

// Items for sale:
// Gizmos - Product number 0-999
// Widgets - Product number 1000-1999
// doohickeys - Product number 2000-2999
// thingamajigs - Product number 3000-3999
// Product number >3999 = Invalid Item

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

float ProdNumb; // Product Number

double PrG; // Product Number for Gizmo
double NG; // Number of items
double PG; // Price of Item

double PrW; // Product Number for Widgets
double NW; // Number of items
double PW; // Price of Item


double PrD; // Product Number for Doohickeys
double ND ; // Number of items
double PD ; // Price of Item


double PrT; // Product Number for Thingamajigs
double NT; // Number of items
double PT; // Price of Item


double PrI; //Product Number for Invalid (> 3999)
double NI; // Number of items
double PI; // Price of Item

double total = 0;

int main ()

{

cout << "Enter the product number of the item sold: ";
cin >> ProdNumb;

while (ProdNumb != -1)
{
if (ProdNumb >= 0 && ProdNumb <= 999)
{
	ProdNumb == PrG;
cout << "Enter the number of items sold: ";
cin >> NG;
cout << "Enter the price of one of the items sold: ";
cin >> PG;
}
cout << "Enter the product number of the item sold: ";
cin >> ProdNumb;

else (ProdNumb >= 1000 && ProdNumb <= 1999)
{
	ProdNumb == PrW;
cout << "Enter the number of items sold: ";
cin >> NW;
cout << "Enter the price of one of the items sold: ";
cin >> PW;	   


cout << "Enter the product number of the item sold: ";
cin >> ProdNumb;
}

else (ProdNumb >= 2000 && ProdNumb <= 2999)
{
	ProdNumb == PrD;
cout << "Enter the number of items sold: ";
cin >> ND;
cout << "Enter the price of one of the items sold: ";
cin >> PD;	   

cout << "Enter the product number of the item sold: ";
cin >> ProdNumb;
}

else (ProdNumb >= 3000 && ProdNumb <= 3999)
{
	ProdNumb == PrT;
cout << "Enter the number of items sold: ";
cin >> NT;
cout << "Enter the price of one of the items sold: ";
cin >> PT;


cout << "Enter the product number of the item sold: ";
cin >> ProdNumb;
}

else (ProdNumb <= -2 && ProdNumb == 0 && ProdNumb >= 4000)
{
	ProdNumb == PrI;
cout << "Enter the number of items sold: ";
cin >> NI;
cout << "Enter the price of one of the items sold: ";
cin >> PI;
				


cout << "Enter the product number of the item sold: ";
cin >> ProdNumb;
}
}

cout << "***** Product Sales Summary *****";
cout << "n";
cout << "n";

cout << "Gizmo Count: ";
total += NG;
cout << NG;
cout << "n";
cout << "Gizmo Sales Total: ";
cout << (NG)*(PG);
cout << "n";
cout << "n";

cout << "Widget Count: ";
total += NW;
cout << NW;
cout << "n";
cout << "Widget Sales Total: ";
cout << (NW)*(PW);
cout << "n";
cout << "n";

cout << "Dookickey Count: ";
total += ND;
cout << ND;
cout << "n";
cout << "Doohickey Sales Total: ";
cout << (ND)*(PD);
cout << "n";
cout << "n";

cout << "Thingamajig Count: ";
total += NT;
cout << NT;
cout << "n";
cout << "Thingamajig Sales Total: ";
cout << (NT)*(PT);
cout << "n";
cout << "n";

cout << "Invalid Sales: ";
total += NI;
cout << NI;

return 0;
}

Solution 1:

This code is not correct because after the if statement is closed with ‘}’ in this code, there are two statements before the else statement starts. There must not be any statements between the closing curly bracket ‘}’ of if statement and the else statement. It can be fixed by simply removing the part that I have marked in red.

Conclusion

And that’s it, I hope you were able to fix the expected primary-expression before error. This article wasn’t easy to write – I’m in no way an expert in C++, but I do know it to a decent level. I couldn’t find any articles related to fixing this error on the internet so I thought I’d write one myself. Answers that I read in forums helped me immensely while researching for this article and I’m thankful to the amazing community of programmers that we have built! If you would like to ask me anything, suggest any changes to this article or simply would like to write for us/collaborate with us, visit our Contact page. Thank you for reading, I hope you have an amazing day.

Also, tell me which one of the 6 types were you experiencing in the comments below.

I know this is a common question but the truth is every code is different. Sometimes it’s hard to apply the concept to your code, it does not work. So please help me. What is wrong with this code? I got it from GitHub. I’m trying to compile it first before I can do a little modification, it sends temp and humidity data to ThingSpeak cloud servers.

#include <DHT.h>  // Including library for dht
#include <ESP8266WiFi.h>

String api_key = "YOUR API KEY"; // Enter your Write API key from ThingSpeak
const char *ssid = "YOUR WIFI SSID"; // replace with your wifi ssid and wpa2 key
const char *pass = "YOUR WIFI PASSWORD";
const char* server = "api.thingspeak.com";

#define DHTPIN 1 // pin where the dht11 is connected
DHT dht;

WiFiClient client;

void setup() {
  Serial.begin(115200);
  delay(10);
  pinMode(2, OUTPUT);
  digitalWrite(2, 0);
  Serial.println("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, pass);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");
}

void loop() {
  int chk = DHT.read(DHTPIN);
  float hum = DHT.humidity;
  float temp = DHT.temperature;
  if (isnan(hum) || isnan(temp)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }
  if (client.connect(server, 80)) {
    // "184.106.153.149" or api.thingspeak.com
    String data_to_send = api_key;
    data_to_send += "&field1=";
    data_to_send += hum;
    data_to_send += "&field2=";
    data_to_send += temp;
    data_to_send += "rnrn";
    client.print("POST /update HTTP/1.1n");
    client.print("Host: api.thingspeak.comn");
    client.print("Connection: closen");
    client.print("X-THINGSPEAKAPIKEY: " + api_key + "n");
    client.print("Content-Type: application/x-www-form-
    urlencodedn");
    client.print("Content-Length: ");
    client.print(data_to_send.length());
    client.print("nn");
    client.print(data_to_send);
    delay(1000);
    Serial.print("Temperature: ");
    Serial.print(temp);
    Serial.print(" degrees Celcius, Humidity: ");
    Serial.print(hum);
    Serial.println("%. Send to Thingspeak.");
  }
  client.stop();
  Serial.println("Waiting...");
  // ThingSpeak needs minimum 15 sec delay between updates, I've set it to 30 seconds
  delay(10000);
}

When I compile I get this error,

  Arduino: 1.8.10 (Windows 10), Board: "NodeMCU 1.0 (ESP-12E 
  Module), 80 MHz, Flash, 
  Legacy (new can return nullptr), All SSL ciphers (most 
  compatible), 
 4MB (FS:2MB OTA:~1019KB), 2, v2 Lower Memory, Disabled, None, Only Sketch, 115200"

    C:UsersAgent 96Desktopthingspeakthingspeak.ino: In function 'void loop()':

   thingspeak:37:20: error: expected primary-expression before '.' token

  int chk = DHT.read(DHTPIN);

                ^

  thingspeak:38:22: error: expected primary-expression before '.' token

  float hum = DHT.humidity;

                  ^

  thingspeak:39:23: error: expected primary-expression before '.' token

  float temp = DHT.temperature;

                   ^

  Multiple libraries were found for "DHT.h"
  Used: C:UsersAgent
  Not used: C:UsersAgent
  Multiple libraries were found for "ESP8266WiFi.h"
  Used: C:UsersAgent
  exit status 1
  expected primary-expression before '.' token

  This report would have more information with
  "Show verbose output during compilation"
   option enabled in File -> Preferences.

Please help, I’m kind of a beginner.