diff --git a/tool/plinko/lib/cmp.c b/tool/plinko/lib/cmp.c index 131700343..47542a739 100644 --- a/tool/plinko/lib/cmp.c +++ b/tool/plinko/lib/cmp.c @@ -19,21 +19,31 @@ #include "tool/plinko/lib/plinko.h" /** - * Compares LISP data structures. + * Compares LISP data structures * - * (cmp 𝑥 𝑥) ⟹ eq everything's equal to itself - * (≡ 𝑥 𝑦) ⟶ (≡ (cmp 𝑥 𝑦) 'eq) (eq) and (cmp) agree if (eq) returns t - * (≡ (cmp 𝑥 𝑦) 'eq) ⟺ (equal 𝑥 𝑦) (cmp) returns eq iff (equal) returns t - * (cmp (ℶ x 𝑦) (ℶ x 𝑦)) ⟹ eq i.e. this does deep comparisons - * (cmp ⊥ 𝑥) ⟹ lt nil is less than everything non-nil - * (cmp 𝑥 ⊥) ⟹ t comparisons are always symmetric - * (cmp 𝑖 𝑗) ⟹ lt atom vs. atom compares unicodes - * (cmp 𝑖𝑗 𝑘𝑙) ⟺ (cmp (𝑖 𝑗) (𝑘 𝑙)) atom characters treated like lists - * (cmp 𝑖 (x . 𝑦)) ⟹ lt atom vs. cons is always less than - * (cmp (x . 𝑦) (x . 𝑦)) ⟹ eq cons vs. cons just recurses - * (cmp (𝑥) (⊥ 𝑦)) ⟹ t e.g. cmp returns gt because 𝑥 > ⊥ - * (cmp (𝑥) (𝑧 𝑦)) ⟹ lt e.g. cmp returns lt because ⊥ < (𝑦) - * (cmp (x . 𝑦) (x 𝑦)) ⟹ lt e.g. cmp returns lt because 𝑦 < (𝑦) + * (≷ 𝑥 𝑦) ⟹ (⊥) | ⊥ | ⊤ + * + * Where + * + * (⊥) means less than a.k.a. -1 + * ⊥ means equal a.k.a. 0 + * ⊤ means greater than a.k.a. +1 + * + * The comparison is performed as follows: + * + * (≷ 𝑥 𝑥) ⟹ ⊥ everything's equal to itself + * (≡ 𝑥 𝑦) ⟶ (≡ (≷ 𝑥 𝑦) ⊥) (eq) and (cmp) agree if (eq) returns t + * (≡ (≷ 𝑥 𝑦) ⊥) ⟺ (equal 𝑥 𝑦) (cmp) returns eq iff (equal) returns t + * (≷ (ℶ x 𝑦) (ℶ x 𝑦)) ⟹ ⊥ i.e. this does deep comparisons + * (≷ ⊥ 𝑥) ⟹ (⊥) nil is less than everything non-nil + * (≷ 𝑥 ⊥) ⟹ ⊤ comparisons are always symmetric + * (≷ 𝑖 𝑗) ⟹ (⊥) atom vs. atom compares unicodes + * (≷ 𝑖𝑗 𝑘𝑙) ⟺ (≷ (𝑖 𝑗) (𝑘 𝑙)) atom characters treated like lists + * (≷ 𝑖 (x . 𝑦)) ⟹ (⊥) atom vs. cons is always less than + * (≷ (x . 𝑦) (x . 𝑦)) ⟹ ⊥ cons vs. cons just recurses + * (≷ (𝑥) (⊥ 𝑦)) ⟹ ⊤ e.g. cmp returns gt because 𝑥 > ⊥ + * (≷ (𝑥) (𝑧 𝑦)) ⟹ (⊥) e.g. cmp returns lt because ⊥ < (𝑦) + * (≷ (x . 𝑦) (x 𝑦)) ⟹ (⊥) e.g. cmp returns lt because 𝑦 < (𝑦) * * @return -1, 0, +1 */