---

name: evaluate-boolean-expression locale: caveman-ultra source_locale: en source_commit: 82c77053 fence_basis_commit: 82c77053 translator: "Julius Brussee homage — caveman" translation_date: "2026-04-24" description: > Evaluate and simplify Boolean expressions using truth tables, algebraic laws (De Morgan, distributive, absorption, idempotent, consensus), and Karnaugh maps for up to six variables. Use when you need to reduce a Boolean expression to its minimal sum-of-products or product-of-sums form, verify logical equivalence between two expressions, or prepare a minimized function for gate-level implementation. license: MIT allowed-tools: Read Grep Glob WebFetch WebSearch metadata: author: Philipp Thoss version: "1.0" domain: digital-logic complexity: basic language: multi tags: digital-logic, boolean-algebra, truth-tables, karnaugh-maps, simplification

Evaluate Boolean Expression

Reduce Boolean expr → minimal form. Parse → canonical, truth table, algebraic laws, K-map (≤6 vars), verify equivalent to original.

Use When

• Simplify before map to gates
• Verify 2 exprs equivalent
• Generate minimal SOP or POS
• Teach/review Boolean algebra
• Prep for design-logic-circuit

In

• Required: Boolean expr any common notation (e.g., A AND (B OR NOT C), A * (B + C'), A & (B | ~C))
• Required: Target form — minimal SOP, POS, or both
• Optional: Variable ordering preference for K-map
• Optional: Don't-care conditions (minterms/maxterms unspecified)
• Optional: Second expr for equivalence check

Do

Step 1: Parse + Canonical

Convert to standard internal rep.

1. Tokenize: Vars (letters/short names), ops (AND, OR, NOT, XOR, NAND, NOR), parens.
2. Op notation: Consistent — * AND, + OR, ' NOT, ^ XOR.
3. Var count: Unique vars. Assign bit (A=MSB, ... Z=LSB default or provided).
4. Canonical SOP: Expand → sum of all minterms via X = X*(Y + Y').
5. Canonical POS: Alt → product of all maxterms via X = X + Y*Y'.

## Normalized Expression
- **Variables**: [A, B, C, ...]
- **Variable count**: [n]
- **Original expression**: [as given]
- **Canonical SOP (minterms)**: Sigma m(i, j, k, ...)
- **Canonical POS (maxterms)**: Pi M(i, j, k, ...)
- **Don't-care set**: d(i, j, ...) [if any]

→ Expr converted canonical SOP/POS w/ all min/maxterms listed, don't-cares separated.

If err: syntax/precedence ambiguous → clarify. Standard: NOT (highest) > AND > XOR > OR (lowest). >6 vars → K-map needs Quine-McCluskey.

Step 2: Truth Table

Build complete table for behavior over all inputs.

1. Rows: All 2^n combos binary order (000, 001, 010, ...).
2. Eval: Sub values → compute output (0/1).
3. Don't-cares: Mark X instead of 0/1.
4. Cross-check minterms: Rows w/ output 1 match minterm list Step 1.

## Truth Table
| A | B | C | F |
|---|---|---|---|
| 0 | 0 | 0 | _ |
| 0 | 0 | 1 | _ |
| ... | ... | ... | ... |

→ Complete 2^n rows, outputs match canonical, don't-cares marked.

If err: table disagrees w/ canonical → recheck Step 1 expansion. Common: misapply De Morgan during canonical → verify each step.

Step 3: Algebraic Simplify

Reduce via Boolean identities.

1. Identity/null: A + 0 = A, A * 1 = A, A + 1 = 1, A * 0 = 0.
2. Idempotent: A + A = A, A * A = A.
3. Complement: A + A' = 1, A * A' = 0.
4. Absorption: A + A*B = A, A * (A + B) = A.
5. De Morgan: (A * B)' = A' + B', (A + B)' = A' * B'.
6. Distributive: A * (B + C) = A*B + A*C, A + B*C = (A + B) * (A + C).
7. Consensus: A*B + A'*C + B*C = A*B + A'*C (B*C redundant).
8. XOR: A*B' + A'*B = A ^ B.
9. Document each step: Expr after each law, cite law.

## Algebraic Simplification Trace
1. Original: [expression]
2. Apply [law name]: [result]
3. Apply [law name]: [result]
...
n. Final algebraic form: [simplified expression]

→ Step-by-step reduction w/ law citations, converging simpler. Trace = verifiable proof.

If err: no further simplify but non-minimal → Step 4 (K-map). Algebraic ≠ guaranteed global min — depends on order.

Step 4: K-map Minimize

Provably minimal SOP/POS (≤6 vars).

1. Draw: Gray code on axes.
   • 2 vars: 2x2
   • 3 vars: 2x4
   • 4 vars: 4x4
   • 5 vars: two 4x4 stacked
   • 6 vars: four 4x4 stacked
2. Fill: 1s (minterms), 0s (maxterms), Xs (don't-cares).
3. Group adj 1s: Rectangular groups of 1, 2, 4, 8, 16, 32 (powers of 2). Wrap edges. Include don't-cares if enlarge.
4. Prime implicants: Each group → product term. Constant vars appear, changing eliminated.
5. Essential prime implicants: Minterms covered by only 1 PI → essential.
6. Cover remaining: Fewest additional PIs (Petrick's if needed).
7. Minimal expr: Combine selected PIs → minimal SOP. For POS group 0s.

## K-map Result
- **Prime implicants**: [list with covered minterms]
- **Essential prime implicants**: [list]
- **Minimal SOP**: [expression]
- **Minimal POS**: [expression, if requested]
- **Literal count**: [number of literals in minimal form]

→ Minimal SOP/POS fewest literals, all PIs documented.

If err: ambiguous (multiple minimal covers) → list all equivalent. >6 vars → Quine-McCluskey tabular or Espresso heuristic, note change.

Step 5: Verify

Confirm logical equivalence simplified vs original.

1. Truth table compare: Eval simplified all 2^n → compare Step 2. Every non-don't-care row must match.
2. Algebraic proof (optional): Derive original from simplified (vice versa) via Step 3 laws.
3. Spot-check: All-zeros, all-ones, tricky simplification inputs.
4. Document: Equivalence holds? Final minimal form.

## Equivalence Verification
- **Method**: [truth table comparison / algebraic proof / both]
- **Mismatched rows**: [none, or list row numbers]
- **Verdict**: [Equivalent / Not equivalent]
- **Final minimal expression**: [the verified result]

→ Simplified matches original all non-don't-care. Final min form clear.

If err: mismatch → trace Steps 3-4. Common: incorrect K-map grouping (non-rect / non-power-of-2), forget wrap, group 0 cell.

Check

• All vars accounted for
• Canonical SOP/POS lists correct min/maxterms
• Truth table 2^n rows correct outputs
• Don't-cares handled (in groups, not coverage req)
• Algebraic steps cite law + verifiable
• K-map Gray code both axes
• All groups rect + power-of-2
• Essential PIs identified
• Simplified matches on non-don't-care
• Final = min literals

Traps

• K-map adjacency: Leftmost/rightmost cols + top/bottom rows adjacent (wrap). Essential for largest groups.
• Non-power-of-2 groups: 3 or 5 cells. Must be 1, 2, 4, 8, 16, 32. Irregular ≠ valid product.
• Ignore don't-cares: Treating as 0s not using to enlarge. Include when reduces, but not required for coverage.
• Precedence err: Assuming AND/OR equal. Standard: NOT > AND > OR. A + B * C ≠ (A + B) * C.
• Stop at algebraic: Local min not global. Cross-check K-map (Quine-McCluskey >6 vars) to confirm.
• Min vs maxterm: Minterms = AND (products) in SOP. Maxterms = OR (sums) in POS. m3 3 vars = A'BC; M3 = A+B'+C'.

→

• design-logic-circuit — map minimized expr → gate-level
• argumentation — structured logical reasoning, shares formal logic