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# Minigraf: Expression Clauses Demo

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# Demonstrates arithmetic filter predicates and

# arithmetic binding expressions (Phase 7.2b).

#

# Run with: cargo run < demos/demo_expr.txt

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# 1. COMPARISON FILTERS

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# [(op ?var value)] filters rows where the predicate holds.

# Supported operators: < > <= >= = !=

# Type mismatches are silently dropped (not an error).

(transact [[:alice :person/name "Alice"] [:alice :person/age 30]

[:bob :person/name "Bob"] [:bob :person/age 17]

[:carol :person/name "Carol"] [:carol :person/age 25]])

# Find adults (age >= 18)

# Expected: "Alice", "Carol"

(query [:find ?name

:where [?e :person/name ?name]

[?e :person/age ?age]

[(>= ?age 18)]])

# Find people younger than 28

# Expected: "Bob", "Carol"

(query [:find ?name

:where [?e :person/name ?name]

[?e :person/age ?age]

[(< ?age 28)]])

# Find people whose name is exactly "Alice"

# Expected: "Alice"

(query [:find ?name

:where [?e :person/name ?name]

[(!= ?name "Bob")]])

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# 2. TWO-VARIABLE COMPARISONS

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# Both sides of the operator can be variables.

(transact [[:match-1 :home-score 3] [:match-1 :away-score 1]

[:match-2 :home-score 2] [:match-2 :away-score 2]

[:match-3 :home-score 0] [:match-3 :away-score 2]])

# Find matches where home team won (home-score > away-score)

# Expected: :match-1

(query [:find ?match

:where [?match :home-score ?h]

[?match :away-score ?a]

[(> ?h ?a)]])

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# 3. ARITHMETIC BINDINGS

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# [(expr) ?result] binds the result of an arithmetic

# expression to a new variable.

# Operators: + - * / (integer division truncates; div-by-zero drops row)

(transact [[:order-1 :price 10] [:order-1 :qty 3]

[:order-2 :price 25] [:order-2 :qty 2]])

# Compute line total

# Expected: [[:order-1 30], [:order-2 50]] (order may vary)

(query [:find ?order ?total

:where [?order :price ?p]

[?order :qty ?q]

[(* ?p ?q) ?total]])

# Apply a 10% tax (integer arithmetic — result truncated)

# Expected: [[:order-1 33], [:order-2 55]] (order may vary)

(query [:find ?order ?with-tax

:where [?order :price ?p]

[?order :qty ?q]

[(* ?p ?q) ?subtotal]

[(* ?subtotal 11) ?scaled]

[(/ ?scaled 10) ?with-tax]])

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# 4. ARITHMETIC COMBINED WITH AGGREGATION

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(transact [[:item-a :cost 40] [:item-a :markup 10]

[:item-b :cost 60] [:item-b :markup 15]])

# Sum the selling prices (cost + markup) across all items

# Expected: [[125]] (50 + 75)

(query [:find (sum ?price)

:where [?i :cost ?c]

[?i :markup ?m]

[(+ ?c ?m) ?price]])

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# 5. TYPE-CHECK PREDICATES

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# (string? ?x), (integer? ?x), (float? ?x),

# (boolean? ?x), (nil? ?x)

# Used as filters or as bindings (return true/false).

(transact [[:v1 :val "hello"]

[:v2 :val 42]

[:v3 :val 3.14]])

# Keep only string values

# Expected: [[:v1 "hello"]]

(query [:find ?e ?v

:where [?e :val ?v]

[(string? ?v)]])

# Bind type-check result as a variable

# Expected: two rows — one true, one false for each entity

(query [:find ?e ?is-int

:where [?e :val ?v]

[(integer? ?v) ?is-int]])

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# 6. STRING PREDICATES

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# (starts-with? ?s prefix), (ends-with? ?s suffix),

# (contains? ?s substring), (matches? ?s regex)

(transact [[:file-a :path "src/main.rs"]

[:file-b :path "src/lib.rs"]

[:file-c :path "tests/integration.rs"]

[:file-d :path "README.md"]])

# Find Rust source files

# Expected: src/main.rs, src/lib.rs, tests/integration.rs

(query [:find ?path

:where [?f :path ?path]

[(ends-with? ?path ".rs")]])

# Find files in src/

# Expected: src/main.rs, src/lib.rs

(query [:find ?path

:where [?f :path ?path]

[(starts-with? ?path "src/")]])

# Find files matching a regex (any .rs file with "lib" in name)

# Expected: src/lib.rs

(query [:find ?path

:where [?f :path ?path]

[(matches? ?path "lib.*\\.rs$")]])

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# 7. EXPR INSIDE not BODY

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(transact [[:prod-a :product/name "Widget"] [:prod-a :product/price 50]

[:prod-b :product/name "Gadget"] [:prod-b :product/price 200]])

# Find products that are NOT expensive (price <= 100)

# Expected: "Widget"

(query [:find ?name

:where [?p :product/name ?name]

[?p :product/price ?price]

(not [(> ?price 100)])])

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# 8. EXPR IN A RULE BODY

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(transact [[:student-a :grade 85]

[:student-b :grade 55]

[:student-c :grade 72]])

(rule [(passing ?s) [?s :grade ?g] [(>= ?g 70)]])

# Expected: :student-a, :student-c

(query [:find ?s

:where (passing ?s)])

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# 9. TEMPORAL QUERIES WITH EXPR CLAUSES

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# :as-of and :valid-at compose with expression filters

# and arithmetic bindings.

# --- tx-time (:as-of) ---

(transact [[:prod-x :item/price 80]])

(transact [[:prod-y :item/price 120]])

# Current: both products exist; only prod-x is under 100

# Expected: [:prod-x]

(query [:find ?e

:where [?e :item/price ?p]

[(< ?p 100)]])

# As of first item transact (only prod-x was recorded)

# Sections 1–8 issued several transacts; adjust :as-of to the tx

# counter printed after the prod-x transact.

# Expected: [:prod-x]

(query [:find ?e

:as-of 9

:where [?e :item/price ?p]

[(< ?p 100)]])

# --- valid-time (:valid-at) ---

# Prices that were valid during a promotional period

(transact {:valid-from "2024-11-01" :valid-to "2024-11-30"}

[[:promo-a :promo/price 50]])

(transact {:valid-from "2024-11-01" :valid-to "2024-11-30"}

[[:promo-b :promo/price 200]])

# During November 2024, find promotions under 100

# Expected: [:promo-a]

(query [:find ?e

:valid-at "2024-11-15"

:where [?e :promo/price ?p]

[(< ?p 100)]])

# Outside the promotion window, no results

# Expected: no results

(query [:find ?e

:valid-at "2025-01-01"

:where [?e :promo/price ?p]

[(< ?p 100)]])

EXIT

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# Summary

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# FILTER PREDICATES:

# [(< ?x ?y)] [(> ?x ?y)] [(= ?x ?y)]

# [(<= ?x ?y)] [(>= ?x ?y)] [(!= ?x ?y)]

#

# ARITHMETIC BINDINGS:

# [(+ ?a ?b) ?result] [(- ?a ?b) ?result]

# [(* ?a ?b) ?result] [(/ ?a ?b) ?result]

# Integer division truncates; divide-by-zero drops row silently.

# Int/float mixing promotes to float.

#

# TYPE CHECKS:

# [(string? ?x)] [(integer? ?x)] [(float? ?x)]

# [(boolean? ?x)] [(nil? ?x)]

# Can be used as a filter or bound: [(string? ?x) ?flag]

#

# STRING PREDICATES:

# [(starts-with? ?s "prefix")]

# [(ends-with? ?s "suffix")]

# [(contains? ?s "substring")]

# [(matches? ?s "regex")] — invalid regex → parse error

#

# TYPE MISMATCH:

# Applying a numeric operator to a non-numeric value

# silently drops that row — it is not an error.

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