#
# Print the first 100 prime numbers.
#
# The program is structured for clarity:
# - A helper method determines whether a number is prime.
# - A generator method collects primes until reaching the desired count.
# - Comments explain the reasoning behind each step.
#
def prime?(n)
#
# Return true if n is a prime number.
#
# The method uses a straightforward and efficient approach:
# - Reject numbers below 2.
# - Only test divisors up to the square root of n.
# Using i * i <= n avoids repeated Math.sqrt calls.
#
return false if n < 2
i = 2
while i * i <= n
return false if n % i == 0 # Found a divisor → not prime
i += 1
end
true # No divisors found → prime
end
def first_n_primes(count)
#
# Generate an array containing the first `count` prime numbers.
#
# The method increments through natural numbers,
# checks primality, and collects primes until the array is full.
#
primes = []
number = 2 # Start from the first prime candidate
while primes.length < count
primes << number if prime?(number)
number += 1
end
primes
end
#
# Main execution: compute and print the first 100 primes.
# Each prime is printed on its own line.
#
first_n_primes(100).each { |p| puts p }
#
# run:
#
# 2
# 3
# 5
# 7
# 11
# 13
# 17
# 19
# 23
# 29
# 31
# 37
# 41
# 43
# 47
# 53
# 59
# 61
# 67
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# 127
# 131
# 137
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# 149
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# 157
# 163
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# 199
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# 223
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# 239
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# 367
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# 383
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# 401
# 409
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# 439
# 443
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# 457
# 461
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# 491
# 499
# 503
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# 521
# 523
# 541
#
