Dart vs FxDart › #16 · Compound interest table

Compound interest table

FxDart wins

• range
• scan
• map

Requirement

Print a year-by-year balance table for $1000 at 5% compound interest over six years — one line per year, starting from the year-0 opening balance, each amount formatted to two decimals. The constants are in the code below; both versions must print the lines shown under Expected output.

year 0: $1000.00
year 1: $1050.00
year 2: $1102.50
year 3: $1157.63
year 4: $1215.51
year 5: $1276.28
year 6: $1340.10

Side by side

Why they differ

A running balance is a running fold, and core Dart has no word for it: fold gives only the final value, so the native version falls back to a loop that seeds a list with the year-0 line, mutates balance, and appends — the compounding rule, the iteration, and the formatting all share one body. FxDart's scan turns each intermediate balance into a value in the pipeline: the seed is the year-0 row, the compounding rule is one pure function, and formatting is a separate map step. Want the year the balance first passes $1200? Chain a filter — the loop version has to grow another flag instead.