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Nim / Control Flow

when compile-time

Learn when compile-time in Nim with a construct-specific explanation, unique example, engineering boundary, and mastery check.

10 min read • Beginner

when compile-time is a focused Nim topic inside Control Flow. This lesson explains the construct itself, the state or value it operates on, and the observable result it produces.

Read the example as a small executable experiment. Identify the exact syntax that belongs to when compile-time, then change one input and predict the result before running it.

Topic-specific example

nim-02-08-when-compile-time.nim
nim Try It Live 
when defined(windows): echo "win"
else: echo "other"
Edge case / engineering note

when compile-time has rules that are easy to miss when the example is copied mechanically. Check the feature-specific boundary shown by this construct: scope, mutability, evaluation order, type constraints, lifetime, error behavior, compile-time restrictions, or resource cleanup where applicable.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

when compile-time Mastery Check →
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