Case 021

Fibonacci sequence (iterative)

fibonacci_sequence.eml generates the first 15 Fibonacci numbers using a while loop with two running variables (a, b) that are swapped and advanced each iteration — deliberately iterative, since recursion is already covered elsewhere in this corpus (examples/phase6-control-flow/ covers a similar iterative shape for a single Fibonacci value; this case generates the whole sequence as a list and prints both the full sequence and its last term).

ok: true — round-trip fixpoint reached (python1 == python2)updated 2026-07-19

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EML

eml

# Self-authored for the EML case corpus (no external origin). Generates the
# first N Fibonacci numbers iteratively — two running variables updated in a
# `while` loop — not via recursion, which is already covered elsewhere in
# this corpus.

def first_n_fibonacci(n):
    sequence^+[]
    a^+0
    b^+1
    count^+0
    while count < n:
        sequence + [a] => sequence
        a + b => next_value
        b => a
        next_value => b
        count^+1
    return sequence

first_n_fibonacci(15) => fib_sequence
"First 15 Fibonacci numbers: " + str(fib_sequence) => sequence_message
sequence_message^0

fib_sequence[len(fib_sequence) - 1] => last_value
"15th Fibonacci number: " + str(last_value) => last_message
last_message^0

Python (deterministic transpilation)

python

def first_n_fibonacci(n):
    sequence = []
    a = 0
    b = 1
    count = 0
    while count < n:
        sequence = sequence + [a]
        next_value = a + b
        a = b
        b = next_value
        count += 1
    return sequence

fib_sequence = first_n_fibonacci(15)
sequence_message = "First 15 Fibonacci numbers: " + str(fib_sequence)
print(sequence_message)
last_value = fib_sequence[len(fib_sequence) - 1]
last_message = "15th Fibonacci number: " + str(last_value)
print(last_message)

stdout (executed)

text

First 15 Fibonacci numbers: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377]
15th Fibonacci number: 377

Trace event types

eml:run:starteml:defeml:calleml:assigneml:augmenteml:returneml:outputeml:run:done