SQR - mkilgore/QB64pe GitHub Wiki

The SQR function returns the square root of a numerical value.

Syntax

square_root = SQR(value)
  • The square root returned is normally a SINGLE or DOUBLE numerical value.
  • The value parameter can be any positive numerical type. Negative parameter values will not work!
  • Other exponential root functions can use fractional exponents(^) enclosed in parenthesis only. EX: root = c ^ (a / b)
Example 1: Finding the hypotenuse of a right triangle: 
 '' ''
 A% = 3: B% = 4
 PRINT "hypotenuse! ="; SQR((A% ^ 2) + (B% ^ 2)) '' ''

 hypotenuse = 5

Example 2: Finding the Cube root of a number. 

 '' ''
 number = 8
 cuberoot = number ^ (1/3)
 PRINT cuberoot '' ''

 2

Example 3: Negative roots return fractional values of one. 

 '' ''
 number = 8
 negroot = number ^ -2
 PRINT negroot '' ''

 .015625
Explanation: A negative root means that the exponent value is actually inverted to a fraction of 1. So x ^ -2 actually means the result will be: 1 / (x ^ 2).
Example 4: Fast Prime number checker limits the numbers checked to the square root (half way). 
DEFLNG P
DO
PRIME = -1   'set PRIME as True
INPUT "Enter any number to check up to 2 million (Enter quits): ", guess$
PR = VAL(guess$)
IF PR MOD 2 THEN              'check for even number
  FOR P = 3 TO SQR(PR) STEP 2 'largest number that could be a multiple is the SQR
    IF PR MOD P = 0 THEN PRIME = 0: EXIT FOR 'MOD = 0 when evenly divisible by another
  NEXT
ELSE : PRIME = 0 'number to be checked is even so it cannot be a prime
END IF
IF PR = 2 THEN PRIME = -1 '2 is the ONLY even prime
IF PR = 1 THEN PRIME = 0  'MOD returns true but 1 is not a prime by definition
IF PRIME THEN PRINT "PRIME! How'd you find me? " ELSE PRINT "Not a prime, you lose!"
LOOP UNTIL PR = 0 '' ''

Enter any number to check up to 2 million (Enter quits): 12379
PRIME! How'd you find me?
Note: Prime numbers cannot be evenly divided by any other number except one.

See also:

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