FA-8896 / Selection controls / Open access

Two-thumb range-slider constraints: The high thumb violates minimum thumb separation · case 01

The high thumb violates minimum thumb separation.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The high separation operation uses `low` where the contract requires `low+gap`.

VERIFIED REPAIR

Implement the high separation operation as `low+gap`.

Unsuccessful approach: Subtracting the gap allows the high thumb below the low thumb.

Case contract

Thumbs clamp to domain and maintain minimum separation; translating preserves span and clamps delta against both domain edges.

Why this case matters

A deterministic model of two-thumb range-slider constraints; this isolates one interface invariant without requiring a browser.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(low, high, target, value, minimum, maximum, gap):
    if target == 'low': low = max(minimum, min(value, high-gap))
    elif target == 'high': high = min(maximum, max(value, low))
    elif target == 'translate':
        delta = max(minimum-low, min(value, maximum-high))
        low += delta; high += delta
    return (low, high)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('low minimum', solve(20, 60, 'low', -10, 0, 100, 10), (0, 60))
check('low gap', solve(20, 60, 'low', 65, 0, 100, 10), (50, 60))
check('high maximum', solve(20, 60, 'high', 120, 0, 100, 10), (20, 100))
check('high gap', solve(20, 60, 'high', 15, 0, 100, 10), (20, 30))
check('translate upper', solve(20, 60, 'translate', 80, 0, 100, 10), (60, 100))
check('translate lower', solve(20, 60, 'translate', -40, 0, 100, 10), (0, 40))
check('ordinary', solve(20, 60, 'low', 30, 0, 100, 10), (30, 60))
check('parameterized range translation', solve(2*N,6*N,'translate',N,0,10*N,N), (3*N,7*N))
for repetition in range(N):
    check('repeat ordinary', solve(20, 60, 'low', 30, 0, 100, 10), (30, 60))
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
low minimum	`[0, 60]`	`[0, 60]`	Passed
low gap	`[50, 60]`	`[50, 60]`	Passed
high maximum	`[20, 100]`	`[20, 100]`	Passed
high gap	`[20, 20]`	`[20, 30]`	Failed
translate upper	`[60, 100]`	`[60, 100]`	Passed
translate lower	`[0, 40]`	`[0, 40]`	Passed
ordinary	`[30, 60]`	`[30, 60]`	Passed
parameterized range translation	`[3, 7]`	`[3, 7]`	Passed
repeat ordinary	`[30, 60]`	`[30, 60]`	Passed

SHA-256 / 5a9bbe5b8563cbefcf41875ba8351e09c5b05fc68df0b311c3cc26612d8db1a5

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(low, high, target, value, minimum, maximum, gap):
    if target == 'low': low = max(minimum, min(value, high-gap))
    elif target == 'high': high = min(maximum, max(value, low-gap))
    elif target == 'translate':
        delta = max(minimum-low, min(value, maximum-high))
        low += delta; high += delta
    return (low, high)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('low minimum', solve(20, 60, 'low', -10, 0, 100, 10), (0, 60))
check('low gap', solve(20, 60, 'low', 65, 0, 100, 10), (50, 60))
check('high maximum', solve(20, 60, 'high', 120, 0, 100, 10), (20, 100))
check('high gap', solve(20, 60, 'high', 15, 0, 100, 10), (20, 30))
check('translate upper', solve(20, 60, 'translate', 80, 0, 100, 10), (60, 100))
check('translate lower', solve(20, 60, 'translate', -40, 0, 100, 10), (0, 40))
check('ordinary', solve(20, 60, 'low', 30, 0, 100, 10), (30, 60))
check('parameterized range translation', solve(2*N,6*N,'translate',N,0,10*N,N), (3*N,7*N))
for repetition in range(N):
    check('repeat ordinary', solve(20, 60, 'low', 30, 0, 100, 10), (30, 60))
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
low minimum	`[0, 60]`	`[0, 60]`	Passed
low gap	`[50, 60]`	`[50, 60]`	Passed
high maximum	`[20, 100]`	`[20, 100]`	Passed
high gap	`[20, 15]`	`[20, 30]`	Failed
translate upper	`[60, 100]`	`[60, 100]`	Passed
translate lower	`[0, 40]`	`[0, 40]`	Passed
ordinary	`[30, 60]`	`[30, 60]`	Passed
parameterized range translation	`[3, 7]`	`[3, 7]`	Passed
repeat ordinary	`[30, 60]`	`[30, 60]`	Passed

SHA-256 / 2bbbdebed76a8e0fa838556b0704e01b1ce7796db6d1e95917930487dcbc2afb

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(low, high, target, value, minimum, maximum, gap):
    if target == 'low': low = max(minimum, min(value, high-gap))
    elif target == 'high': high = min(maximum, max(value, low+gap))
    elif target == 'translate':
        delta = max(minimum-low, min(value, maximum-high))
        low += delta; high += delta
    return (low, high)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('low minimum', solve(20, 60, 'low', -10, 0, 100, 10), (0, 60))
check('low gap', solve(20, 60, 'low', 65, 0, 100, 10), (50, 60))
check('high maximum', solve(20, 60, 'high', 120, 0, 100, 10), (20, 100))
check('high gap', solve(20, 60, 'high', 15, 0, 100, 10), (20, 30))
check('translate upper', solve(20, 60, 'translate', 80, 0, 100, 10), (60, 100))
check('translate lower', solve(20, 60, 'translate', -40, 0, 100, 10), (0, 40))
check('ordinary', solve(20, 60, 'low', 30, 0, 100, 10), (30, 60))
check('parameterized range translation', solve(2*N,6*N,'translate',N,0,10*N,N), (3*N,7*N))
for repetition in range(N):
    check('repeat ordinary', solve(20, 60, 'low', 30, 0, 100, 10), (30, 60))
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
low minimum	`[0, 60]`	`[0, 60]`	Passed
low gap	`[50, 60]`	`[50, 60]`	Passed
high maximum	`[20, 100]`	`[20, 100]`	Passed
high gap	`[20, 30]`	`[20, 30]`	Passed
translate upper	`[60, 100]`	`[60, 100]`	Passed
translate lower	`[0, 40]`	`[0, 40]`	Passed
ordinary	`[30, 60]`	`[30, 60]`	Passed
parameterized range translation	`[3, 7]`	`[3, 7]`	Passed
repeat ordinary	`[30, 60]`	`[30, 60]`	Passed

SHA-256 / c5bcab482e6424907206e6ec681d206c66b535482629e5f2619ebb054c6c6d72

Verification & scope

This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:38:25.376216+00:00.

Case digest / 512fffa818bb72a678fb0f0143bfbf22ac5eb25639249c2fa9c27b36ccf558bd