GOALSEEK_PACKAGE

const GOALSEEK_PACKAGE: IEnginePackage;

Defined in: packages/engine/src/packages/goalseek/GoalSeekPackage.ts:33

Goal seek, inverting a line against a target.

solve line 4 for rate = 900 reads as “find the value of rate that makes line 4 equal 900”. It is the answer to the forwards-only engine’s one standing gap: every “what input gives me this answer” otherwise means editing a number and re-reading the result until it looks right (see GitHub issue #98). The relationship comes from a line reference, so there is a well-defined target to solve against without inventing any syntax for the relationship itself, the line already expresses it.

Grammar and search live apart, the same split every other package here uses:

• GoalSeekNormalizerRule fuses the bare word solve into a GOAL_SEEK token, but only directly before a LINE_REF, so solve(x^2-4=0, x) (the algebra verb) and :solve = 2 (a variable) are both untouched.
• GoalSeekParselet reads line N for <var> = <target> and emits the plugin call.
• GoalSeekPluginFunctions does the work: a closed-form inversion when the line is closed form in the variable, a bounded, hard-capped numeric search otherwise. See its module doc for the search domain, the monotonicity assumption, and the iteration cap.

Trigger-word decision: solve is never a bare lexer keyword (it is the product’s own name and a plausible variable), so, exactly like the algebra verbs’ own symbolic:call rule, it is fused only in the one shape that means goal seek, solve immediately before a line reference.