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do

do evaluates all expressions in sequence, sharing a context between them. This effectively forms a sub program and is useful for combining with other functions that require exactly 1 expression, like an if: (if .condition (do (step-1) (step-2)))

do purposefully makes its child expressions have side effects, so that setting variables has an effect on subsequent expressions.

Examples

  • (do true 42) ➜ 42
  • (do (set! $foo 1) (+ $foo 2)) ➜ 3

Forms

(do expr:expression…) ➜ any

  • expr is 1 or more expressions

do evaluates sets up a new context and then evaluates all expressions in sequence, sharing the context between them, forming a sub program. The return value of do is the return value of the last expression in it.

When any expression encounters an error, do stops evaluation and returns the error.

Context

do shares a context between all child expressions.