Add eager if(cond, t, f) builtin#20
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What: - Register `if(cond, t, f)` in Builtins(). Truthy condition picks t; falsey picks f. Both branches always evaluate. - Rewrite the Go `if` keyword token to a sentinel identifier in preprocessSource so the parser accepts the call. The rewrite uses the same scheme already in place for `map`; the rewrite list is factored out so future additions stay symmetric. - Translate the sentinel back via displayIdent in evalIdent, resolveCallable, and prewalk so user-visible env entries, registered shadows, error messages, and the prepared-func cache all key on "if". - Update templates.md and higher-order-patterns.md to use `if(cond, t, f)` instead of the brittle `cond && t || f` idiom. Update spec.md and llms.txt to document the new builtin. Why: - `if(cond, t, f)` reads cleanly even when both branches are non-nil values, where `cond && t || f` silently picks `f` whenever `t` happens to be falsey. - Consolidating the keyword-rewrite plumbing keeps the next addition (`?.` / `?[` in step 7) easy and consistent.
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What
if(cond, t, f)as an eager builtin. Truthy condition returnst, falsey returnsf. Both branches always evaluate.ifkeyword token to a sentinel before parsing, mirroring the existingmaprewrite. The keyword-rewrite list is factored out so future additions stay symmetric.displayIdentinevalIdent,resolveCallable, andprewalkso env entries, registered shadows, error messages, and the prepared-func cache all key on the user-visible name"if".templates.mdandhigher-order-patterns.mdto useif(cond, t, f)instead of the brittlecond && t || fidiom. Updatespec.mdandllms.txtto document the new builtin.Why
if(cond, t, f)reads cleanly even when both branches are non-nil values, wherecond && t || fsilently picksfwheneverthappens to be falsey. Consolidating the keyword-rewrite plumbing also keeps the next addition (?./?[in step 7) easy and consistent.Test plan
go test ./...go test -race ./...go test -run=^$ -fuzz=FuzzCompile -fuzztime=20s .go test -run=^$ -fuzz=FuzzEval -fuzztime=20s .