Doubles/floats
- Range of +/- 1.7e308 |
- 16 digits of precision |
- Overflow = +/- inf, underflow = 0 |
- Double = 8b, float = 4b |
- Floats are less precise, used in Arduino |
Integers
- Max value is +/-2147483647 |
- 2 or 4 bytes |
Vari changes
- Short int x: half the byte size of int (half range) |
- Long int x: double byte size of int (double range) |
- Unsigned: positive numbers (double range) |
Functions
- Usually double, int, void (depends on what you want to return) |
- type _name(what it inputs){} |
Arduino
- void setup () is used to initialized variables and configurations |
- pinMode (pin1, OUTPUT) means that the pin will have a output role |
- Serial.begin(115200) initializes for print out |
- void loop () runs the code repeatedly, like while(1) |
- use float instead of double |
- digitalWrite(pin1, HIGH) sets the pin to have 5V |
- Serial.print( ) will print to the IDE |
- micros()*1.0e-6 is time in s |
- digital is 0V or 5V, analog is continuous |
Arrays/dynamic
- Always starts at 0 |
- Dynamic array is only for 1D |
- 2D arrays: A[row][column] |
- Size must be an int |
- A[] is allowed, not A[][] |
- A[i]++; means increase the value of A[i] by 1 |
Dynamic array:
double *A;
int n; // which we'll use for input
A = new double [n];
if(A == NULL){
// check if it exists and can run code
cout << "\nerror in dynamic allocation";
exit(1);
}
delete[] A;
A = nullptr;
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Char/strings
- Used for strings |
- String is char array |
- Max range of -128/127 |
- '\0' is the term char |
- char a = ''a'' |
- For space, ' ' |
| |
- Always make char size 100 or 1000 |
Reverse string:
void string_reverse(char str1[], char str2[]){
int i=0;
int counter=0;
while(str1[i] != '\0'){
counter++;
i++; // this finds string length
}
for (i=0;i<counter;i++){
str2[i] = str1[counter -1 -i]; // because at counter its '\0'
}
str2[counter] = '\0'; // to stop the string
}
Files
- ofstream fout // writing to file |
- ifstream fin // reading file |
- fout.close() at end of file part |
- create file: fout.open(".txt") |
- have #include <fstream> |
Check error:
if (!fout or !fin){
cout << "\nerror with file";
exit(1);
}
Pointers
- Can store anything (int, double, function, etc) |
- int*b checks what's inside b |
- p = &b means p is b's address |
- *(&b)=b is simply the address of b |
- *p=11 means there's 11 stored inside b |
- *(p+1) increments the pointer |
- *p +1 increments what's inside p |
- For char, it prints everything after the address |
- For double it prints what's at the specific address |
Special info
- Break to stop loop |
- Bool has 1 = true and 0 = false |
- Exit(0) to stop program |
- && means and |
- Dot product: sum+= A[i] * B[i] |
- || means or |
- cout <<scientific << setprecision(9) |
- sizeof(int) =4 |
- sizeof(double) = 8 |
- sizeof (bool) = 1 |
- sizeof(float)=4 |
Call by reference:
&x means that it brings changes to main, not a copy of x
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Examples
Transpose:
for (i=0;i<3;i++){
for (j=0;j<3;j++){
tA[i][j] = A[j][i];
Dynamic array:
double *p1;
n = 10 or cin >> n;
p1 = new double [n];
if (p1 == NULL) return 1;
delete p1;
No_space:
void no_space ( char str1 []) {
int i, newsize=0;
for (i=0; str1[i]; i++){
if (str1[i]!=' '){
str1[newsize]=str1[i];
newsize++;
}
}
str1[newsize]='\0';
}
Alternating string:
j = 0;
for(i=0;i<n_min;i++) {
str3[j] = str1[i]; j++;
str3[j] = str2[i]; j++;
}
for(i=n_min;i<n_max;i++) {
if(n_max == n1) str3[j] = str1[i];
else str3[j] = str2[i]; j++;
}
str3[j] = '\0';
Arduino example:
float t0, t, v = 30;
int p;
int input0;
float v0;
// a)
servo1.attach(3);
servo1.write(0);
delay(1000); // wait for the servo
// b) (30 deg / s)
t0 = micros()*1.0e-6; // initial time
// p = p0 + v(delta_t) = p0 + v(t-t0)
// trajectory
while(1) {
t = micros()*1.0e-6;
p = v*(t-t0); // trajectory
servo1.write(p);
if(p >= 90) break;
}
while(1) {
input0 = analogRead(A0);
v0 = (input0/1023.0)*5;
// convert int to volts
if(v0 > 3) break;
}
servo1.write(0);
delay(1000);
exit(0);
}
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